According to the Washington Post, the problem of AIDS in Africa was overstated. In the worst example, the actual infection rate in Rwanda is a tenth of what was previously assumed - 3% instead of 30%. The original figures came from tests done on women during pre-natal examinations. As it turns out, sexually active women living in urban centers who have access to pre-natal care are much more likely to have AIDS than the general population.
That explains where the exaggerated numbers came from. It does not explain why they were accepted. This has to do with issue advocates and their relationship with media and policy makers.
If a reporter or a legislator needs information on a subject, they normally go to an expert. This is fine if the expert happens to be an expert because of the type of work he does. Asking an engineer for advice on bridges is a safe choice.
The problem comes when the expert is also an advocate for the issue at hand. They are often very biased, exaggerating threats and denigrating contrary evidence. In this case, an entire UN organization was created separate from the WHO to work on AIDS in Africa. Between the prestige and the billions in funding, people from this organization are unlikely to announce that they threat was never as big as originally believed.
I have referred to Dr. James Hansen from NASA as a Global Warming evangelist. That is because he is a true believer and wants to convert everyone else. He is on record as exaggerating the facts. A decade ago he predicted a .8 degree rise in global temperature. It only rose .2 degrees. When asked about this he admitted that he exaggerated the expected increase in order to get attention.
This constantly happens with issue advocates. In one notorious case, advocates for missing children claimed that 30,000 children were kidnapped each year. It later turned out that they had taken the number of children who were reported missing each year from all causes (mainly run-aways and parental custody disputes) and attributed them all to kidnapping by a stranger.
This sort of exaggeration is almost universal and is usually taken at face value by reporters. Worse, the reporters become converted and start acting as advocates themselves. Opponents of the issue are usually scrutinized and dismissed as having been paid off by some corporate interest or another. Nearly anyone who disputed warming is assumed to be a pawn of the oil companies (for lack of a better target).
Advocates have other harmful behaviors. In the case of AIDS, the original advocates were gays who feared that they would not sufficient funding unless the population was convinced that they were at risk, also. Accordingly, any studies on how AIDS is transmitted are discouraged. The truth of the matter is that the transmission rate between heterosexual couples is very low. Nearly every case in the US can be attributed to an exchange of blood, either through needles or gay sex. Twenty years ago when AIDS started appearing in hookers it was predicted that this was the beginning of its spread into heterosexual America. This never happened. AIDS in America is still limited to drug-users (many of whom earn money for their drugs by hooking) and gays.
Because of the gay lobby in the US, no study has ever been done on AIDS transmission in Africa. In Rwanda the numbers are low enough that the original studies could have been inflated by drug-using prostitutes. In other countries the populace could be infected through improperly-sterilized medical equipment. No one will look so no one knows.
In my last post I complained about the way that Global Warming is presented. Not only is it given as a fact but it is always given as a disaster. The issue advocates are at work here. They make sure that no one can hear about any possible benefits. The cause is more important that the truth.
Is there a solution? Not that I can see. The best advice I can offer is that the more someone insists in the urgency of his cause the more skeptical one should be.