1. Overview.
A. Estimating the spread of HIV/AIDS among MSM.
B. Reviewing the history of the projections.
C. What the future may hold.
2. National Strategy on HIV/AIDS.
3. More References.
18.3.10
1. OVERVIEW.
A. Estimating the Spread of HIV/AIDS among MSM.
Statistical models are tools.
Diagnosed infections are counted and sorted by relevant criteria. Incidence rates and prevalence ratios and baseline assumptions are fed into the process whereby epidemiologists assess the available evidence and offer recommendations to help society respond to an outbreak of disease. Projections help form the basis for contingencies at multiple levels -- from the individual person, to the local community, to the nation and, in the HIV/AIDS pandemic, right through to the international level.
The CDC's data is the basis for the 30% by 30 forecast. In 1994, epidemiologists at Columbia University reported that the CDC's data led them to forecast that
Odets said:
He was not alone in making estimates in that range.
By 2001, researchers at the CDC reported that the HIV prevalence (i.e. those living with infection or with AIDS) in the 15-22 age group
B. Reviewing the history of the projections.
Since the outbreak of HIV/AIDS, the CDC has gathered statistics from across the country. In 2005, the CDC revised and refined its analysis of the available evidence. It released more accurate incidence rates and prevalence ratios.
By that time the indications were that the 30% by age 30 projection had been fulfilled, tragically, in 1995-2005.
In 2005, a leading HIV/AIDS researcher at the CDC, R. Stall, presented his findings at the International AIDS Conference.
He reviewed the historical data and the current trends. Stall calculated the lifelong risk for twenty-year-old homosexually-active men (i.e. men who have sex with men, aka MSM) of becoming infected with HIV. By age 30 -- some ten years hence -- about 25% would be infected; 40% by age 40; and 50% by age 50.
C. What the future may hold.
In 2008, at the Conference on Retroviruses and Opportunistic Infections, R. Stall presented more research and a new projection for coming decades.
Taking as his starting point the current incidence of HIV infection among 15-22 year-old men who have sex with men (MSM), professor Stall ran a mathematic model to see how this would translate into HIV prevalence as the 18-year-old group got older.
In a press conference he explained:
A. Estimating the Spread of HIV/AIDS among MSM.
"Epidemiologists estimate that 30 percent of all 20-year-old homosexually-active men will be HIV positive or dead of AIDS by the time they are 30."
E. Goldman, “Psychological Factors Generate HIV Resurgence in Young Gay Men,” Clinical Psychiatry News, Oct. 1994.
Statistical models are tools.
Diagnosed infections are counted and sorted by relevant criteria. Incidence rates and prevalence ratios and baseline assumptions are fed into the process whereby epidemiologists assess the available evidence and offer recommendations to help society respond to an outbreak of disease. Projections help form the basis for contingencies at multiple levels -- from the individual person, to the local community, to the nation and, in the HIV/AIDS pandemic, right through to the international level.
The CDC's data is the basis for the 30% by 30 forecast. In 1994, epidemiologists at Columbia University reported that the CDC's data led them to forecast that
"lifetime individual risks of seroconversion of over 50 percent, with the highest annual hazard (4.4 percent per year) occurring before age 25 years."In 1994, W. Odets, a clinical psychiatrist in California, presented a paper to the international science community on the epidemiology of HIV/AIDS.
Odets said:
"Some simple epidemiology helps answer these questions: To date, more San Franciscans have died of AIDS - 90% of them gay men - than all the San Franciscans dead from the four wars of the 20th century, combined and quadrupled. Nationally, 30 percent of 20 year- old gay men will be infected with HIV or dead of AIDS by age 30. A majority of gay 20 year-olds will contract HIV during their lifetimes. In San Francisco, our current rates of seroconversion will much more than maintain a 50% prevalence of HIV infection indefinitely."Odets is the source for the article that Goldman wrote and which is quoted at the top of this blogpost.
He was not alone in making estimates in that range.
By 2001, researchers at the CDC reported that the HIV prevalence (i.e. those living with infection or with AIDS) in the 15-22 age group
"rose steadily with increasing age, to nearly 10% among 22-year-olds. [...] The emerging data presented here suggest that we may be headed toward a resurgence in HIV infections among MSM".In other words, the prevalence and incidence rates pointed toward fulfilling the 1994 projection quoted at the top of this blogpost.
B. Reviewing the history of the projections.
Since the outbreak of HIV/AIDS, the CDC has gathered statistics from across the country. In 2005, the CDC revised and refined its analysis of the available evidence. It released more accurate incidence rates and prevalence ratios.
By that time the indications were that the 30% by age 30 projection had been fulfilled, tragically, in 1995-2005.
In 2005, a leading HIV/AIDS researcher at the CDC, R. Stall, presented his findings at the International AIDS Conference.
He reviewed the historical data and the current trends. Stall calculated the lifelong risk for twenty-year-old homosexually-active men (i.e. men who have sex with men, aka MSM) of becoming infected with HIV. By age 30 -- some ten years hence -- about 25% would be infected; 40% by age 40; and 50% by age 50.
C. What the future may hold.
In 2008, at the Conference on Retroviruses and Opportunistic Infections, R. Stall presented more research and a new projection for coming decades.
Taking as his starting point the current incidence of HIV infection among 15-22 year-old men who have sex with men (MSM), professor Stall ran a mathematic model to see how this would translate into HIV prevalence as the 18-year-old group got older.
In a press conference he explained:
"The model that we constructed yielded an estimate that at about age 25, about 15% of the men would be HIV positive; by age 35, about a third; and by age 40, about 41%."He continued:
"We were kind of horrified that our model yielded prevalence estimates that high.
[...]
What we find is that the model actually fits exactly what's going on in terms of HIV prevalence among gay men, at least in America's largest urban centers. This model that we are extrapolating based on the incidence rates, which culminates in an HIV prevalence rate of 40% at age 40, is not a prediction of something that may happen one day. We are describing epidemiological phenomena that are occurring all around us, and will continue to occur among young American men, if we do not find ways to lower HIV incidence rates further."
The rest of this series of blogposts expands on each section (A to C) of this overview. References are included.
Return to Table of Contents.
A. Estimating the spread of HIV/AIDS among MSM.
In 1994 Erik Goldman, reporting for the Clinical Psychiatry News, wrote that:
The researcher had based his projection on data from the Centers for Disease Control's surveillance of the HIV/ADS epidemics across the US.
Early data and early trends.
In 1991, about a decade after the start of the HIV/AIDS epidemic, the American Journal of Epidemiology published the research of Hoover and colleagues.
Based on their analysis of the historical spread of HIV infection in homosexual and bisexual men, the team of researchers projected the growth of the epidemic among that subpopulation.
See: Donald R. Hoover (1991) Estimating the 1978-1990 and future spread of human immunodeficiency virus type 1 in subgroups of homosexual men. American Journal of Epidemiology. 134, 10: 1190-205.
Morris and Dean are Epidemiologists at Columbia University. In 1994 their research on HIV/AIDS appeared in The American Journal of Epidemiology, which is published by Johns Hopkins University School of Hygiene and Public Health.
Lifelong risk of infection.
Walter Odets is a clinical psychologist in San Francisco. According to his website, Odets has "written extensively about the psychological and social issues of gay men and gay communities, HIV prevention, and the US AIDS epidemic."
In 1994 he wrote about the available evidence on HIV prevalence, incidence, and risk for homosexualy-active men: "Reinventing HIV Prevention for Gay Men".
Also: Odets, (1994) AIDS Education and Harm Reduction for Gay Men: Psychological Approaches for the 21st Century. AIDS & Public Policy Journal. 9, 1: 1 - 15.
Resurgence among homosexually-active men.
Odets was cited by Wolitski and collegues in their 2001 research paper, "Are We Headed for a Resurgence of the HIV Epidemic Among Men Who Have Sex With Men?"
It was published in American Journal of Public Health Vol. 91, No. 6, pg 883-888. They are with the National Center for HIV, STD, and TB Prevention, Centers for Disease Control and Prevention.
The researchers cited a leading CDC researcher, R. Stall, who wrote in 1994 that the best way to lose the fight against HIV among MSM is to declare victory and leave the field.
In 2005, at the 16th International AIDS Conference, R. Stall, a leading CDC researcher presented his paper, "Emerging HIV Epidemics among Gay and non-Gay Identified MSM".
He calculated the lifelong risk for twenty-year-old homosexually-active men (i.e. men who have sex with men, aka MSM) of becoming infected with HIV. By age 30 -- some ten years hence -- about 25% would be infected; 40% by age 40; and 50% by age 50.
A young black twentysomething is at higher risk: 50% infected by age 40 and about 75% by age 50. He estimated that 1 in 3 would not know that they had been infected.
This is not a test of faith -- of blindly believing -- but epidemiologists do substantiate their work and they expect that as the epidemic continues to unfold their assumptions, analyses, modelling, and projections will be tested by surveillance of HIV/AIDS.
In 1994 Erik Goldman, reporting for the Clinical Psychiatry News, wrote that:
"HIV/AIDS is rampant in the homosexual community. Epidemiologists estimate that 30 percent of all 20-year-old homosexually-active men will be HIV positive or dead of AIDS by the time they are 30."He was referring to a paper written by a San Francisco clinical pychiatrist who presented it to a meeting comprised of international scientists who were studying HIV and clinicians who were treating people with HIV. That event eventually grew into the Conference on Retroviruses and Opportunistic Infections which has become the most important annual conference on HIV/AIDS. The researchers were among the leading pioneers in the fight against HIV/AIDS.
Goldman, “Psychological Factors Generate HIV Resurgence in Young Gay Men,” Clinical Psychiatry News, Oct. 1994.
The researcher had based his projection on data from the Centers for Disease Control's surveillance of the HIV/ADS epidemics across the US.
Early data and early trends.
In 1991, about a decade after the start of the HIV/AIDS epidemic, the American Journal of Epidemiology published the research of Hoover and colleagues.
Based on their analysis of the historical spread of HIV infection in homosexual and bisexual men, the team of researchers projected the growth of the epidemic among that subpopulation.
Future seroconversion among homosexual men was predicted assuming that the "stabilized" 1986-1990 hazards (stratified by age) observed here will be representative of future rates. [...] [A] seronegative 20-year-old [...] has a 20.2% chance of serocon-verting before reaching the age of 25 years (a 4.4% yearly hazard). The annual hazard drops to 2.5% between 25 and 30 years, to about 1.5% between 30 and 45 years, and to 1.0% between 45 and 55 years. The overall probability of seroconversion prior to age 55 years is about 50%, with seroconversion still continuing at and after age 55. Given that this cohort consists of volunteers receiving extensive anti-HIV-1 transmission education, the future seroconversion rates of the general homosexual population may be even higher than those observed here.In other words, a twenty year old MSM had about 30% chance of being HIV-infected by age 30 and about a 50% chance by age 55.
See: Donald R. Hoover (1991) Estimating the 1978-1990 and future spread of human immunodeficiency virus type 1 in subgroups of homosexual men. American Journal of Epidemiology. 134, 10: 1190-205.
Morris and Dean are Epidemiologists at Columbia University. In 1994 their research on HIV/AIDS appeared in The American Journal of Epidemiology, which is published by Johns Hopkins University School of Hygiene and Public Health.
The current levels of unsafe sex reported in the Longitudinal AIDS Impact Project are shown to be almost exactly on the epidemic threshold. If this behavior were maintained, HIV prevalence would slowty decline in the population, but with just one additional unsafe sexual partner per year HIV would instead become endemic, with seroprevalence of about 65% in the oldest group and about 25% in the youngest.See: Morris, M., Dean, L. (1994) Effects of Sexual Behavior Change on Long-Term Human Immunodeficiency Virus Prevalence among Homosexual Men. American Journal of Epidemiology. 140, 3: 217 - 32.
[...]
Cohort studies continue to document annual seroconversion rates of 1-2 percent per year or higher in some groups [...] this leads to lifetime individual risks of seroconversion of over 50 percent, with the highest annual hazard (4.4 percent per year) occurring before age 25 years.
Lifelong risk of infection.
Walter Odets is a clinical psychologist in San Francisco. According to his website, Odets has "written extensively about the psychological and social issues of gay men and gay communities, HIV prevention, and the US AIDS epidemic."
In 1994 he wrote about the available evidence on HIV prevalence, incidence, and risk for homosexualy-active men: "Reinventing HIV Prevention for Gay Men".
Some simple epidemiology helps answer these questions: To date, more San Franciscans have died of AIDS - 90% of them gay men - than all the San Franciscans dead from the four wars of the 20th century, combined and quadrupled. Nationally, 30 percent of 20 year-old gay men will be infected with HIV or dead of AIDS by age 30. A majority of gay 20 year-olds will contract HIV during their lifetimes. In San Francisco, our current rates of seroconversion will much more than maintain a 50% prevalence of HIV infection indefinitely.Clinical psychiatrist, Walt Odets wrote and presented a paper for the Dallas Prevention Summit of the Gay and Lesbian Medical Association: "Young Gay and Bisexual Men".
Younger men thus engaged our hopes that they would not have to suffer with AIDS, and they have been burdened with our expectations that the epidemic could be brought to an end in the gay and bisexual communities. By 1990 it had become clear that very young men would suffer with AIDS. In 1992 the San Francisco Department of Health estimated (by means of a voluntary enlistment study) that 15 percent of 20 to 24 year old gay-identified men were already HIV infected, and young gay and bisexual men seeking services at San Francisco city STD clinics have shown an astonishing 40 percent infection rate. Because the young, in general, seek fewer medical services than older individuals, the level of ELISA testing among young men is unknown. It is thus possible that infection rates are higher than those seen in the self-selected study groups that generate our current figures. The projections we do have suggest that 30 percent of 20 year old gay men will be infected with HIV or dead of AIDS by age 30, and that a majority will become HIV infected during their lifetimes. [Odets' emphasis.]See: Odets, Ph.D., "Psychosexual and Educational Challenges for the Gay and Bisexual Male Communities," a report to the American Association of Physicians for Human Rights, AIDS Prevention Summit, Dallas, Texas, July 15-17, 1994.
Also: Odets, (1994) AIDS Education and Harm Reduction for Gay Men: Psychological Approaches for the 21st Century. AIDS & Public Policy Journal. 9, 1: 1 - 15.
Resurgence among homosexually-active men.
Odets was cited by Wolitski and collegues in their 2001 research paper, "Are We Headed for a Resurgence of the HIV Epidemic Among Men Who Have Sex With Men?"
It was published in American Journal of Public Health Vol. 91, No. 6, pg 883-888. They are with the National Center for HIV, STD, and TB Prevention, Centers for Disease Control and Prevention.
The HIV prevalence rate for MSM is substantially higher than that for the general population. In a population-based study of MSM in 4 major metropolitan areas conducted from 1996 through 1998, 18% of participants, compared with less than 1% of the overall population, reported that they were HIV-seropositive. Compared with older MSM, younger MSM have lower HIV prevalence rates, but they are at substantial risk for infection over time. According to a 7-city study of MSM aged 15 to 22 years conducted from 1994 through 1998, 7% were infected with HIV. Although none of the 15-year-olds in this study were infected, the rates of infection rose steadily with increasing age, to nearly 10% among 22-year-olds.
[...]
The emerging data presented here suggest that we may be headed toward a resurgence in HIV infections among MSM, unless we act decisively to reevaluate, refocus, and reinvigorate our prevention efforts.
The researchers cited a leading CDC researcher, R. Stall, who wrote in 1994 that the best way to lose the fight against HIV among MSM is to declare victory and leave the field.
In 2005, at the 16th International AIDS Conference, R. Stall, a leading CDC researcher presented his paper, "Emerging HIV Epidemics among Gay and non-Gay Identified MSM".
He calculated the lifelong risk for twenty-year-old homosexually-active men (i.e. men who have sex with men, aka MSM) of becoming infected with HIV. By age 30 -- some ten years hence -- about 25% would be infected; 40% by age 40; and 50% by age 50.
A young black twentysomething is at higher risk: 50% infected by age 40 and about 75% by age 50. He estimated that 1 in 3 would not know that they had been infected.
This is not a test of faith -- of blindly believing -- but epidemiologists do substantiate their work and they expect that as the epidemic continues to unfold their assumptions, analyses, modelling, and projections will be tested by surveillance of HIV/AIDS.
Return to Table of Contents.
B. Reviewing the history of the projections.
As noted in Part A of this series, Goldman reported on a paper by clinical psychiatrist Walt Oteds who had referred to the work of HIV/AIDS researchers and epidemiologists most of whom worked with the CDC.
At that time they were looking forward from the vatange point of 1994; for now let's look backward to the period 1994-2005.
While epidemiologists use very sophisticated statistical modelling for reviewing the history of epidemics, and for projecting estimates of the spread of disease, we can also do a very simple back-of-envelope review of the CDC's historical data on the HIV/AIDS epedimic for the period leading up to 2005. We need data broken down by age and category of transmission; and we need to use basic assumptions from sero-surveys and the like. This will give readers a general idea of the available evidence and it will provide a test of the plausibity of the projections cited earlier.
Please note that the epidemiology of HIV/AIDS is documented in peer-reviewed research and this is just a basic simulation of a much more sophisticated process.
Here are a couple of ways to look back and compare with the projection that was made in 1994.
The 1994 projection:
Scenario 1.
Based on 10-year average of 13,000 diagnosed infections per year.
Range of estimates of new HIV infection. By 1995, there was a wide range of estimates for projecting HIV incidence -- as high as 90,000 per year for all cases. However, modest estimates used a mid-range such as 10,000 infections per year among homosexually-active men (MSM); and another 3,000 per year among homosexually-active men who had used injection drugs (MSM & IDU).
Tracking 20 year-olds. Looking back on 1985-2004, the CDC reported that .05% of all HIV incidences in 1985-1995 were among the under 20 age group, and 13.2% among the 20-29 age group in 1996-2000, and 12% among that group in 2001-2004. This covers the ten year period during which men who were 20 years old in 1995 became 30 years old in 2005.
Undiagnosed cases. Assuming that the homosexually-active subpopulation is 4% the general male population, there were 80,000 homosexually active men of that age in 1995. Among these men, thousands became infected with HIV/AIDS. The CDC has estimated that diagnosed cases represented about 75% of all infections. So thousands more new HIV infections went unreported.
Estimating HIV infection by age 30. Now, using these parameters, we can estimate the number of new HIV infections among homosexually active men and then calculate the infected share of the homosexual men who reached 30 years old by 2005.
Accordingly, in 1995 only a few 20-year-olds had been infected; but in 1996-2000 about 8,600 of that age cohort had been infected; and another 6,200 by 2004. The accumulated total would have been about 14,800 which represented 75% of all infections. This means that by 2005 about 20,000 homosexually-active men had been infected by age 30 years (diagnosed and undiagnosed).
That would be about 25% of the homosexual male population in that age group.
Scenario 2.
Based on counting the newly diganosed infections by interim periods.
The subpopulation size. In 1995 there were 2 million men aged 20 years in the general population. Of these, about 80 thousand (4%) were homosexually-active. By the end of the following decade, thousands of these young homosexually-active men were living with or were dead due to HIV/AIDS.
Proportion of new cases by age. In its 25th year review of the epidemic, the CDC reported that 0.5% of new HIV infections had occured to the under 20 age group by 1995, 13% to the 20-29 age group by 2000, and 12% to the 20-29 group by 2004. The cohort that was 20 in 1995 passed through the decade and accumulated thousands of new diagnosed cases of HIV.
Number of new cases by transmission. Infections transmitted by men who had sex with men (MSM) and MSM who used injected drugs (MSM & IDU) are referred to here as MSM infections. The CDC estimated 325,200 new MSM infections in 1985-1995, another 106,200 in 1996-2000, and another 74,735 in 2001-2004. About 72% of all new infections among men were MSM in 1985-1995 and 60% in 1996-2000 and in 2001-2004.
Estimated number and proportion of homosexually-active men who, by the year 2005, had been infected by age 30. At age 20 about 1,600 had already been infected; five years later another 14,000; and five years later another 9,000 newly infected. About 24,600 HIV infections had accumulated among those who became 30 years old in 2005.
Expressed as a percentage: Of the 80,000 homosexually active men who were 20 years old in 1995, about 24,600 (30%) had been infected with HIV/AIDS by age 30.
Summary.
Of course, epidemiologists use much more sophisticated modelling to compare projections to the history of epidemics; and, also, to construct and to refine models to forecast the near and distant future spread of disease. However, given the CDC's count of diagnosed infections, and the assumptions regarding undiagnosed infections and the size of the MSM subpopulation, it is plausible that the 1994 projection regarding twenty-year-olds was realized.
In 2006 there were over 1 million infected people in the US; and yet, even with all the awareness programs and the identification of risk factors and improvements in testing, that number must be read with the caution that probably another 300 thousand people do not know they are already infected.
Here is a quote from the CDC's review of HIV/AIDS epidemiology 25 years after the outbreak:
The CDC's data for 2006 showed that in that year alone almost 40% (11,000) of newly infected homosexually-active men were under the age of thirty. Assuming that represents only 75% of all infections, as per the CDC, then in 2006 there were almost 14,500 new infections -- diagnosed plus undiagnosed -- in the under-30 age group.
The basis for the back-of-envelope scenario #1 above, is that there would be about 13,000 new infections per year, on average, amongs MSM of all ages during 1995-2005. So if the average climbs closer toward 14,5000, then, it could be that more than 30% of twenty-year-olds will be infected by age 30.
How the data might break-down by age group during the next ten-twenty years, time will tell. At some point a saturation of the subpopulation is reached and growth is slowed to the rate at which young people who enter the sexually active population become infected.
For now we rely on the epidemiological modelling that produces the most plausible projections. We can look back in ten years and compare to see how well the prjection did.
References:
As noted in Part A of this series, Goldman reported on a paper by clinical psychiatrist Walt Oteds who had referred to the work of HIV/AIDS researchers and epidemiologists most of whom worked with the CDC.
At that time they were looking forward from the vatange point of 1994; for now let's look backward to the period 1994-2005.
While epidemiologists use very sophisticated statistical modelling for reviewing the history of epidemics, and for projecting estimates of the spread of disease, we can also do a very simple back-of-envelope review of the CDC's historical data on the HIV/AIDS epedimic for the period leading up to 2005. We need data broken down by age and category of transmission; and we need to use basic assumptions from sero-surveys and the like. This will give readers a general idea of the available evidence and it will provide a test of the plausibity of the projections cited earlier.
Please note that the epidemiology of HIV/AIDS is documented in peer-reviewed research and this is just a basic simulation of a much more sophisticated process.
Here are a couple of ways to look back and compare with the projection that was made in 1994.
The 1994 projection:
Epidemiologists estimate that 30 percent of all 20-year-old homosexually-active men will be HIV positive or dead of AIDS by the time they are 30.
E. Goldman, “Psychological Factors Generate HIV Resurgence in Young Gay Men,” Clinical Psychiatry News, Oct. 1994.
Scenario 1.
Based on 10-year average of 13,000 diagnosed infections per year.
Range of estimates of new HIV infection. By 1995, there was a wide range of estimates for projecting HIV incidence -- as high as 90,000 per year for all cases. However, modest estimates used a mid-range such as 10,000 infections per year among homosexually-active men (MSM); and another 3,000 per year among homosexually-active men who had used injection drugs (MSM & IDU).
Tracking 20 year-olds. Looking back on 1985-2004, the CDC reported that .05% of all HIV incidences in 1985-1995 were among the under 20 age group, and 13.2% among the 20-29 age group in 1996-2000, and 12% among that group in 2001-2004. This covers the ten year period during which men who were 20 years old in 1995 became 30 years old in 2005.
Undiagnosed cases. Assuming that the homosexually-active subpopulation is 4% the general male population, there were 80,000 homosexually active men of that age in 1995. Among these men, thousands became infected with HIV/AIDS. The CDC has estimated that diagnosed cases represented about 75% of all infections. So thousands more new HIV infections went unreported.
Estimating HIV infection by age 30. Now, using these parameters, we can estimate the number of new HIV infections among homosexually active men and then calculate the infected share of the homosexual men who reached 30 years old by 2005.
Accordingly, in 1995 only a few 20-year-olds had been infected; but in 1996-2000 about 8,600 of that age cohort had been infected; and another 6,200 by 2004. The accumulated total would have been about 14,800 which represented 75% of all infections. This means that by 2005 about 20,000 homosexually-active men had been infected by age 30 years (diagnosed and undiagnosed).
That would be about 25% of the homosexual male population in that age group.
Scenario 2.
Based on counting the newly diganosed infections by interim periods.
The subpopulation size. In 1995 there were 2 million men aged 20 years in the general population. Of these, about 80 thousand (4%) were homosexually-active. By the end of the following decade, thousands of these young homosexually-active men were living with or were dead due to HIV/AIDS.
Proportion of new cases by age. In its 25th year review of the epidemic, the CDC reported that 0.5% of new HIV infections had occured to the under 20 age group by 1995, 13% to the 20-29 age group by 2000, and 12% to the 20-29 group by 2004. The cohort that was 20 in 1995 passed through the decade and accumulated thousands of new diagnosed cases of HIV.
Number of new cases by transmission. Infections transmitted by men who had sex with men (MSM) and MSM who used injected drugs (MSM & IDU) are referred to here as MSM infections. The CDC estimated 325,200 new MSM infections in 1985-1995, another 106,200 in 1996-2000, and another 74,735 in 2001-2004. About 72% of all new infections among men were MSM in 1985-1995 and 60% in 1996-2000 and in 2001-2004.
Estimated number and proportion of homosexually-active men who, by the year 2005, had been infected by age 30. At age 20 about 1,600 had already been infected; five years later another 14,000; and five years later another 9,000 newly infected. About 24,600 HIV infections had accumulated among those who became 30 years old in 2005.
Expressed as a percentage: Of the 80,000 homosexually active men who were 20 years old in 1995, about 24,600 (30%) had been infected with HIV/AIDS by age 30.
Summary.
Of course, epidemiologists use much more sophisticated modelling to compare projections to the history of epidemics; and, also, to construct and to refine models to forecast the near and distant future spread of disease. However, given the CDC's count of diagnosed infections, and the assumptions regarding undiagnosed infections and the size of the MSM subpopulation, it is plausible that the 1994 projection regarding twenty-year-olds was realized.
In 2006 there were over 1 million infected people in the US; and yet, even with all the awareness programs and the identification of risk factors and improvements in testing, that number must be read with the caution that probably another 300 thousand people do not know they are already infected.
Here is a quote from the CDC's review of HIV/AIDS epidemiology 25 years after the outbreak:
"Analysis of data collected by the National HIV Behavioral Surveillance System, which surveys populations at high risk for HIV to assess prevalence and trends in risk behavior, HIV testing, and use of prevention services, revealed that of MSM surveyed in five U.S. cities, 25% were infected with HIV and of those, 48% were unaware of their infection."The cited study's large sample of homosexually-active men has a median age of 32 years; 76% of those already infected were over the age of 30 years; the highest proportion of unrecognized infection (75%) was among those younger than 30.
The CDC's data for 2006 showed that in that year alone almost 40% (11,000) of newly infected homosexually-active men were under the age of thirty. Assuming that represents only 75% of all infections, as per the CDC, then in 2006 there were almost 14,500 new infections -- diagnosed plus undiagnosed -- in the under-30 age group.
The basis for the back-of-envelope scenario #1 above, is that there would be about 13,000 new infections per year, on average, amongs MSM of all ages during 1995-2005. So if the average climbs closer toward 14,5000, then, it could be that more than 30% of twenty-year-olds will be infected by age 30.
How the data might break-down by age group during the next ten-twenty years, time will tell. At some point a saturation of the subpopulation is reached and growth is slowed to the rate at which young people who enter the sexually active population become infected.
For now we rely on the epidemiological modelling that produces the most plausible projections. We can look back in ten years and compare to see how well the prjection did.
References:
Twenty-Five Years of HIV/AIDS - United States, 1981-2006 [PDF]
TABLE. Estimated numbers and percentages of HIV/AIDS and AIDS cases, by year of diagnosis and selected characteristics - United States, 1981-2004.
Figures 1, 2, and 3, page 591.
Department of health and human services, Centers for Disease Control and Prevention.
Morbidity and Mortality Weekly Report. June 2, 2006 / Vol. 55 / No. 21
Glynn M, Rhodes P. What is really happening with HIV trends in the United States? Modeling the national epidemic. In: Proceedings of National HIV Prevention Conference, Atlanta, GA, June 12-15, 2005.
CDC. Trends in HIV/AIDS diagnoses-33 states, 2001-2004. MMWR 2005;54:1149-53.
CDC. HIV prevalence, unrecognized infection, and HIV testing among men who have sex with men-five U.S. cities, June 2004-April 2005. MMWR 2005;54:597-601.
Table: HIV Prevalence in 2 Probability Telephone Samples of Men Who Have Sex With Men: San Francisco, 1997 and 2002.
Return to Table of Contents.
C. What the future may hold.
As discussed in part A and part B, the 30% by age 30 projection for 1995-2005 appears to have been tragically prescient.
But what of the coming decades?
CDC Revises and Updates.
In 2006 TheBody.com published an article: "HIV/AIDS and Young Men Who Have Sex With Men".
The article cited multiple studies and reports from the CDC.
According to its new detailed analysis of national data, the CDC reported that 53% (28,720) of all new HIV infections were among gay and bisexual men and of those about 38% (10,850) were under the age of 30. Note: that's new infections in 2008 alone.
Each year's number of infected people adds to the next because the survival rate has now vastly improved. The count of those living with HIV/AIDS has been going up by about 30,000 per year. Add to the count of infections those infected who have died in the epidemic.
As a larger share of the subpopulation of homosexually-active men becomes infected, the share of uninfected men shrinks. There may come a point where the rate of increase will slow due to reaching a near-saturation level.
Professor Stall, CROI, and refined CDC evidence.
Credible Sources?
In 2008, AIDSmap reported on the Conference on Retroviruses and Opportunistic Infections (CROI).
AIDSmaps has many funders including UNAIDS and the World Health Organization.
US Centers for Disease Control.
The AIDSmap article cited the the CDC's major statistical report on the epidemic:
Centers for Disease Control and Prevention. Trends in HIV/AIDS diagnoses among men who have sex with men - 33 states, 2001-2006. MMWR 57: 681-686, 2008.
Longtime HIV/AIDS researcher, Ron Stall, presented a major paper at the 2008 the Conference on Retroviruses and Opportunistic Infections in which he made a projection based on updated data from the CDC:
POZ reported on Stall's research and interviewed him:
POZ is
Credible Researcher?
Ron Stall, PhD, MPH, has been a CDC researcher at the Division of HIV/AIDS Prevention; he is currently Professor and Chair of the Department of Behavioral and Community Health Sciences at the Graduate School of Public Health, University of Pittsburgh; more recently he has served as a member of the external peer review panel for the CDC.
He explains his work on HIV/AIDS reasearch:
TheBody.com
TheBody.com is the largest source of HIV and AIDS information on the internet. It covers "HIV prevention, HIV testing, HIV symptoms, HIV/AIDS treatment and HIV/AIDS-related health issues, as well as first-person stories from HIV-positive people."
Here is a transcript from a 2008 press conference that Professor Stall held at one of the most important HIV-related medical conferences of that year [MP3 file available]. He estimated that by age 35 more than 30% of men who have sex with men (MSM) will have been infected with HIV:
Stall has worked as a leading CDC researcher and is recognized as an expert in behavioral epidemiology and the HIV/AIDS epidemic. He has recently estimated that about a third of MSM will be HIV-infected by age 35 and about 40% by age 40.
Conclusion.
Several well-respected sources, each considered highly credible by pro-gay groups and by the CDC and other prominent HIV/AIDS researchers, have been reporting for more than fifteen years now that the risk of HIV-infection is very high for homosexually-active men in the USA.
As suggested by CDC evidence and as estimated by credible HIV/AIDS researchers:
As discussed in part A and part B, the 30% by age 30 projection for 1995-2005 appears to have been tragically prescient.
But what of the coming decades?
CDC Revises and Updates.
In 2006 TheBody.com published an article: "HIV/AIDS and Young Men Who Have Sex With Men".
In 2006, an estimated 56,300 people in the United States became infected with HIV. Of these, 34% -- or approximately 19,000 -- were adolescents or young adults aged 13-29 years.[See table]
Of all age groups of MSM, HIV/AIDS cases increased most among YMSM aged 13-24.[See Graph]
The article cited multiple studies and reports from the CDC.
In one recent study, 77% of young, urban MSM aged 15-29 who tested HIV-positive as part of the study mistakenly believed they were not infected. The percentage was even higher for young black HIV-infected MSM, 90% of whom did not know their infection status. People who don't know they are infected might be less likely to take measures to keep from spreading the virus to others.
[...]
[Y]ounger MSM, who did not witness the toll of AIDS in the early years of the epidemic, might view HIV infection as less dangerous and more treatable, leading them to become complacent about risks.
According to its new detailed analysis of national data, the CDC reported that 53% (28,720) of all new HIV infections were among gay and bisexual men and of those about 38% (10,850) were under the age of 30. Note: that's new infections in 2008 alone.
Each year's number of infected people adds to the next because the survival rate has now vastly improved. The count of those living with HIV/AIDS has been going up by about 30,000 per year. Add to the count of infections those infected who have died in the epidemic.
As a larger share of the subpopulation of homosexually-active men becomes infected, the share of uninfected men shrinks. There may come a point where the rate of increase will slow due to reaching a near-saturation level.
Professor Stall, CROI, and refined CDC evidence.
Credible Sources?
In 2008, AIDSmap reported on the Conference on Retroviruses and Opportunistic Infections (CROI).
The annual Conference on Retroviruses and Opportunistic Infections (CROI) began in 1994 as a small meeting of scientists studying HIV and clinicians treating people with HIV. It is now one of the most important annual HIV gatherings and provides a forum for basic scientists, clinical investigators, and global health researchers to present, discuss, and critique their investigations into the epidemiology and biology of human retroviruses and the diseases they produce.AIDSmap is operated by the worldwide non-profit organization, NAM (National AIDS Manual) whose mission is,
"to support the fight agaist AIDS with independent, accurate, accessible and comprehensive information. We aim to create and disseminate information resources rooted in the experience of those most affected, enabling individuals and communities to take action and control in responding to HIV and AIDS."
AIDSmaps has many funders including UNAIDS and the World Health Organization.
US Centers for Disease Control.
The AIDSmap article cited the the CDC's major statistical report on the epidemic:
Centers for Disease Control and Prevention. Trends in HIV/AIDS diagnoses among men who have sex with men - 33 states, 2001-2006. MMWR 57: 681-686, 2008.
Longtime HIV/AIDS researcher, Ron Stall, presented a major paper at the 2008 the Conference on Retroviruses and Opportunistic Infections in which he made a projection based on updated data from the CDC:
Ron Stall of the University of Pittsburgh [...] said that his systematic review of incidence studies concluded that incidence in community samples of American gay men was around 2.4% a year. Moreover, Stall went on to demonstrate the long term implications of such an incidence rate.
Taking this figure as a starting point, Stall ran a mathematic model to see how this incidence in a group of 18 year-olds would translate into HIV prevalence as the group got older. The key assumptions of the model were that each year 2.4% of the group acquired HIV, and that mortality rates were the same as for equivalent age groups in the general population. By age 20, around 5% of the group would be HIV-positive; by age 25, around 15% would have HIV; by age 30, around 25% would be living with HIV, and when they were 40, 41% of the group would be HIV-positive.
POZ reported on Stall's research and interviewed him:
Stall’s conclusion that HIV prevention wasn’t working well for gay and bisexual men was based on his careful scrutiny of all the available data he could find on HIV incidence, which estimates how many new infections occur each year. He and his colleagues found that by the most conservative estimate, 2.39 percent of gay and bisexual men in the U.S. were becoming infected annually between 1995 and 2005. Stall then calculated what would happen to a group of men who were 20 years old in 1995 and had a 2.39 percent HIV incidence rate. He found that by 2005, when the men had turned 30, nearly a quarter of them were likely to be infected with HIV, and that by 2015, when the men would turn 40, over 40 percent would be HIV positive.
POZ is
"the nation’s leading publication and website about HIV/AIDS. Offering unparalleled editorial excellence, POZ and poz.com are identified by our readers as their most trusted sources of information about the disease. [...] More than 150,000 copies of POZ are distributed at thousands of doctors’ offices and AIDS service organizations nationwide. The magazine is also distributed at the world’s most important and well-attended conferences focusing on HIV/AIDS prevention, treatment and community issues."
Credible Researcher?
Ron Stall, PhD, MPH, has been a CDC researcher at the Division of HIV/AIDS Prevention; he is currently Professor and Chair of the Department of Behavioral and Community Health Sciences at the Graduate School of Public Health, University of Pittsburgh; more recently he has served as a member of the external peer review panel for the CDC.
He explains his work on HIV/AIDS reasearch:
The primary focus of my research has been in HIV prevention and behavioral epidemiology, both in the United States and abroad. I also have conducted numerous research projects in the areas of substance abuse epidemiology, smoking, aging, mental health, and housing as health care. Although a great deal of my research has been conducted among gay men, I also have worked with other populations at high risk of HIV infection and expect to expand on this work.
TheBody.com
TheBody.com is the largest source of HIV and AIDS information on the internet. It covers "HIV prevention, HIV testing, HIV symptoms, HIV/AIDS treatment and HIV/AIDS-related health issues, as well as first-person stories from HIV-positive people."
Here is a transcript from a 2008 press conference that Professor Stall held at one of the most important HIV-related medical conferences of that year [MP3 file available]. He estimated that by age 35 more than 30% of men who have sex with men (MSM) will have been infected with HIV:
Our review, using very stringent review criteria, identified 20 different studies from 1995 to 2005, the protease era in Western Europe, North America and Australia, that yielded, in turn, 65 annualized incidence rates across this period.Also see: Paper presented at the American Association of Physicians for Human Rights, AIDS Prevention Summit, 15-17 July. Dallas, Texas. Paul, J., R Stall.
[T]here were no increases or decreases in incidence rates among MSM in the industrialized countries from 1995 to 2000. Rates are not going up or down. The weighted mean incidence rate across all these countries is 2.5% per year.
Turning to the United States model: We looked at just the estimates for the United States. In community-based samples, which were the lowest rate of HIV incidence, compared to HIV alternative test sites or STD [sexually transmitted disease] samples, we calculated a mean incidence rate of about 2.4% per year.
[We] wanted to find out: What does 2.4% mean? What does 2.4%, in particular, mean over long periods of time? So we did a thought experiment, using a closed cohort of young gay men at the age of 18, none of whom were infected at 18, but calculated an incidence rate of infection of 2.4% per year as these men moved from age 20 to age 40. The model that we constructed yielded an estimate that at about age 25, about 15% of the men would be HIV positive; by age 35, about a third; and by age 40, about 41%.
The reason that we used the age of 40 as our cut-point is that AIDS was discovered a quarter of a century ago. These men would have had to have been, by definition, younger than 15 years of age. In addition, because we know that HIV incidence rates were stable from 1995 to the present, the vast majority of their sexual lives would have been in the context of this background incidence rate of about 2.4 or 2.5%.
We were kind of horrified that our model yielded prevalence estimates that high. And accordingly, we went back and looked at the largest samples published by the CDC [U.S. Centers for Disease Control and Prevention] of prevalence rates among men in the United States. The CDC just published, in 2005, a very large study of HIV prevalence rates, by age, in five American cities. What we find is that the model actually fits exactly what's going on in terms of HIV prevalence among gay men, at least in America's largest urban centers. This model that we are extrapolating based on the incidence rates, which culminates in an HIV prevalence rate of 40% at age 40, is not a prediction of something that may happen one day. We are describing epidemiological phenomena that are occurring all around us, and will continue to occur among young American men, if we do not find ways to lower HIV incidence rates further.
Stall has worked as a leading CDC researcher and is recognized as an expert in behavioral epidemiology and the HIV/AIDS epidemic. He has recently estimated that about a third of MSM will be HIV-infected by age 35 and about 40% by age 40.
Conclusion.
Several well-respected sources, each considered highly credible by pro-gay groups and by the CDC and other prominent HIV/AIDS researchers, have been reporting for more than fifteen years now that the risk of HIV-infection is very high for homosexually-active men in the USA.
As suggested by CDC evidence and as estimated by credible HIV/AIDS researchers:
"30% of all 20-year-old homosexually-active men will be HIV positive or dead of AIDS by the time they are 30."
Return to Table of Contents.
2. National Strategy on HIV/AIDS.
In part C of this series of blogposts, Professor Stall was quoted as having said:
In part C of this series of blogposts, Professor Stall was quoted as having said:
"We are describing epidemiological phenomena that are occurring all around us, and will continue to occur among young American men, if we do not find ways to lower HIV incidence rates further.”In March 2010 the following was reported to the American public. Please be sure to read to the end of the quote where President Obama has used this research to set priorities regarding his national strategy on HIV/AIDS -- and will ask Congress to budget accordingly:
A data analysis released today by the Centers for Disease Control and Prevention underscores the disproportionate impact of HIV and syphilis among gay and bisexual men in the United States.This article was produced and disseminated by the U.S. Centers for Disease Control and Prevention on March 10, 2010.
[...]
While CDC data have shown for several years that gay and bisexual men make up the majority of new HIV and new syphilis infections, CDC has estimated the rates of these diseases for the first time based on new estimates of the size of the U.S. population of MSM. Because disease rates account for differences in the size of populations being compared, rates provide a reliable method for assessing health disparities between populations.
[...]
[The] risk of HIV transmission through receptive anal sex is much greater than the risk of transmission via other sexual activities, and some gay and bisexual men are relying on prevention strategies that may be less effective than consistent condom use.
[...]
Preventing HIV and STDs among gay and bisexual men is a top CDC priority. CDC provides funding to health departments and community-based organizations throughout the nation to implement proven behavior-change programs for MSM and will soon expand a successful HIV testing initiative to reach more gay and bisexual men. Additionally, CDC is implementing an updated National Syphilis Elimination Plan in cities where MSM have been hardest hit by the disease, and will release an updated HIV prevention strategic plan within the next year to support the President's upcoming National HIV/AIDS Strategy. CDC officials note that the new analysis released today underscores the importance of the HIV and STD prevention efforts targeting gay and bisexual men recently announced as part of the President's fiscal year 2011 budget proposal.
Return to Table of Contents.
12.3.10
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