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Estimates on HIV called too high

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  • Scott Geibel
    Now that surveys like the DHS are doing population-based HIV testing in national sample surveys, previous national estimates of HIV prevalence should continue
    Message 1 of 3 , Jun 22, 2004
      Now that surveys like the DHS are doing population-based HIV testing in
      national sample surveys, previous national estimates of HIV prevalence should
      continue to be revised downward- Scott

      Estimates on HIV called too high
      New data cut rates for many nations
      By John Donnelly, Globe Staff | June 20, 2004

      PRETORIA -- Estimates of the number of people with the AIDS virus have been
      dramatically overstated in many countries because of errors in statistical
      models and a possible undetected decline in the pandemic, according to new
      data and specialists on the disease.

      In many nations, analysts are cutting the estimates of HIV prevalence by
      half or more.

      Rwanda, for instance, a new United Nations estimate due out next month will
      put HIV prevalence at about 5 percent, according to Rwandan officials, down
      from more than 11 percent four years ago. In Haiti, a recent unpublished
      study by the Centers for Disease Control and Prevention has found HIV prevalence
      was less than 3 percent, compared with the UN's most recent estimate of
      6 percent. And the numbers in India are coming under increasing scrutiny
      because surveys in AIDS hot spots are indicating a prevalence rate that
      is much lower than the national average.

      Even with lower estimates, health specialists agree that AIDS remains the
      most dangerous pandemic in the developing world. In particular, it threatens
      to ravage societies in southern Africa, and throughout the continent the
      disease has killed millions in the prime of their lives.

      Several AIDS specialists said they think the current estimate of 40 million
      people living with the AIDS virus worldwide is inflated by 25 percent to
      50 percent, based on a wide spectrum of household surveys in nearly a dozen
      countries. That would go against the grain of years of assertions by UNAIDS
      that the disease is relentlessly on the rise.

      A significant downward revision in AIDS and HIV numbers calls into question
      many of the lessons on fighting AIDS that are based on prior estimates.
      It also is likely to affect future budgets and cause many countries to consider
      revising strategies on how to prevent and treat the disease.

      "It is fundamental that we have accurate information of what we're up against,"
      said Robert R. Redfield, cofounder of the University of Maryland's Institute
      of Human Virology and a leading AIDS specialist. "If you are overestimating
      the epidemic, you may attribute positive impacts to things that have nothing
      to do with it."

      UN epidemiologists and statisticians responsible for the current estimates
      acknowledged in interviews that some country figures will be sharply cut
      in a forthcoming report, but they played down any possibility now of a sizable
      reduction in the overall number of infected people. They declined to disclose
      their most recent estimates for 2003, set to be released next month before
      the 15th International AIDS Conference in Bangkok.

      The major error in the estimation of HIV and AIDS numbers has occurred primarily
      because epidemiologists relied too heavily on HIV rates in urban areas and
      failed to factor in much lower prevalence in rural areas, where surveys
      are rare, AIDS specialists said.

      Suggestions that prevalence may be overstated may not be embraced by some
      who work to fight HIV or in countries hard hit by the epidemic. Billions
      of dollars in aid is at stake in the coming years. If HIV seems less menacing,
      more dollars may go to fighting other diseases or may be redirected away
      from global health initiatives entirely.

      Already, earlier this year, US officials told Rwandan AIDS administrators
      that if HIV prevalence estimates were to drop to 5 percent, the country's
      AIDS funding may be cut, according to both US and Rwandan officials, speaking
      on condition of anonymity.

      Another reason behind the plunging rates, some AIDS specialists say, is
      that the pandemic may be slowing.

      The upcoming UNAIDS report is expected to show that HIV prevalence is declining
      in eastern Africa and leveling off or slightly slowing in West Africa, but
      still maintaining a high rate in southern Africa.

      Statisticians traditionally have had a difficult time estimating the size
      of the pandemic. In 1986, Jim Chin, then a state epidemiologist in California
      who later developed models for the World Health Organization to calculate
      HIV prevalence, and several other US officials met in a West Virginia hotel
      room to figure out how many Americans had HIV.

      Chin recollected that the group arrived at a range of 1 million to 1.5 million
      people; 18 years later, the number is at about 1 million Americans. "A lot
      of it was guesswork, based on limited studies," Chin said. "It was the best
      we could do."

      The tools today are much more refined but still based on a long list of
      assumptions.

      More than a decade ago, AIDS researchers in sub-Saharan Africa found that
      HIV tests on blood samples from pregnant women at prenatal clinics provided
      a good indicator of HIV prevalence among adults aged 15 to 49 in countries
      with high rates; early household surveys confirmed the finding.

      But the surveys were limited at first to a few sites in countries. "We were
      talking about four or five urban sites and one or two rural sites, and extrapolating
      that to the whole country. You can see what potential inaccuracies there
      can be with this crude methodology," said Chin, who now is an independent
      AIDS analyst and criticizes UN estimates as overstated.

      Other unknowns contribute to potential errors. One is estimating a country's
      population; the estimates for Nigeria, for instance, range from 120 million
      to 160 million people, but a census of the country has not been completed
      in more than half a century. Another is that most countries do not collect
      data on deaths.

      Once officials from UNAIDS and the WHO arrive at an HIV prevalence estimate
      for a country, they use that estimate to help determine AIDS deaths, AIDS
      orphans, numbers of people needing antiretroviral treatment, and the average
      life expectancy for people in countries. As HIV prevalence numbers are adjusted
      downward, the numbers for the other AIDS-related categories also will be
      readjusted similarly.

      To estimate the number of people dying from AIDS, for instance, epidemiologists
      assume that on average a person will live for eight or nine years after
      infection; they then plot the progression of a country's epidemic, determining
      how many people were infected in each year. If HIV prevalence estimates
      are significantly wrong in any year, estimates for AIDS deaths will be correspondingly
      wrong eight or nine years later.

      Some specialists raised questions about the estimates in mid-January, after
      a report on a household survey in Kenya that estimated a 6.7 percent national
      HIV prevalence rate, compared with the UN's 15 percent estimate in 2002.

      Two weeks later in Addis Ababa, Ethiopia, at a conference on estimating
      HIV and AIDS prevalence, epidemiologist Peter D. Ghys raised the question
      of potentially inflated AIDS rates before several dozen epidemiologists.
      Ghys estimates HIV and AIDS figures for UNAIDS. On the last slide of his
      presentation, Ghys wrote, "Should UNAIDS/ WHO estimates be lowered by 25
      percent?"

      Asked recently about his question, Ghys said he raised it in light of the
      new Kenyan data: "We already had lowered estimates quite a bit in the previous
      year, but since then, we've had additional information that came in somewhat
      lower than our estimates. Maybe it will change again, but it's difficult
      for us to say, yes, it should be 25 percent or something."

      In 2003, the UN revised HIV prevalence in sub-Saharan Africa to 26.6 million
      people, from 29.4 million the year before.

      Ties Boerma, who is in charge of the WHO's estimates on the HIV virus, said
      the UN was preparing to reduce prevalence estimates again this year, although
      not by 25 percent. Yet Chin and several other specialists say new data from
      several countries and from high-risk groups in countries suggest that the
      UN should do so.

      Chin said he thinks the global rate is inflated by 25 percent to 40 percent,
      while two US health officials working on AIDS said they think the global
      numbers may be 50 percent inflated. The two spoke on condition of anonymity.

      Among their reasons:


      In a slum of the Chennai district in India, a high-risk area for transmission
      of HIV because of prostitutes and drug users, a recent household survey
      found 0.2 percent HIV prevalence. The nationwide rate is 0.8 percent, or
      4 million people. Ghys acknowledged: "It's difficult to say what is going
      on in India. In India, there's always a great deal of uncertainty in those
      estimates. Are we sure it's 0.8 percent? The honest answer is no, we are
      not sure."


      A recent household survey in Burkina Faso put the national estimate at 1.9
      percent; the UN's most recent estimate puts the rate at 7 percent. In Africa,
      other recent surveys showing significantly lower rates have been in Zambia,
      South Africa, Mali, and Ghana. Rates also were lowered by a third in Zimbabwe
      because of significant numbers of faulty HIV tests.


      Several years ago, UNAIDS estimated that up to 60 percent of the Angolan
      military was HIV positive. Dr. Richard Shaffer, head of the US Department
      of Defense's HIV/AIDS Prevention Program, said in an interview the estimate
      was "nowhere near close to that. It's 6 to 7 percent. They based the earlier
      number on a small sample, which included people outside the military, and
      extrapolated that to the military as a whole."


      In the late 1980s and early 1990s, HIV prevalence in adults aged 15 to 49
      in Uganda was estimated as high as 30 percent; now HIV prevalence is estimated
      at 5 percent. But now many no longer believe the 30 percent figure, raising
      questions about the true impact of Uganda's much-touted prevention program.
      Said Ghys: "If we recast our estimates, it wasn't 30 percent, it was maybe
      22 or something."

      Earlier this year, the US government announced its first substantial grants
      in President Bush's multibillion-dollar plan to fight AIDS. The news release
      cited a 15 percent HIV prevalence rate in Kenya and a 6 percent rate in
      Haiti, even though US-funded surveys in both countries had recently concluded
      that the rate was at least half those figures.
    • John Patten
      Let me be the next to congratulate Steve Berry. I believe this past weekend was when he got married. Good luck Steve, and send us a photo when you can. JP
      Message 2 of 3 , Jul 7, 2004
        Let me be the next to congratulate Steve Berry. I
        believe this past weekend was when he got married.
        Good luck Steve, and send us a photo when you can.

        JP



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      • Scott Geibel
        I don t know Steve, but this reminds me of a joke: Two unbiased estimators are sitting at a bar having a drink. One asks So how do you like being married?
        Message 3 of 3 , Jul 7, 2004
          I don't know Steve, but this reminds me of a joke:

          Two unbiased estimators are sitting at a bar having a drink. One asks "So
          how do you like being married?" The other one says "It's okay, but you lose
          a degree of freedom."

          Well... at least it gets a chuckle in a room full of social scientists.



          >-- Original Message --
          >To: ujeni@yahoogroups.com
          >From: John Patten <jppatten98@...>
          >Date: Wed, 7 Jul 2004 05:48:20 -0700 (PDT)
          >Subject: [ujeni] Contratulations Steve Berry
          >Reply-To: ujeni@yahoogroups.com
          >
          >
          >Let me be the next to congratulate Steve Berry. I
          >believe this past weekend was when he got married.
          >Good luck Steve, and send us a photo when you can.
          >
          >JP
          >
          >
          >
          >__________________________________
          >Do you Yahoo!?
          >Yahoo! Mail - 50x more storage than other providers!
          >http://promotions.yahoo.com/new_mail
          >
          >

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