By Jill McGivering
The United Nations has reduced its estimates of how many people are infected with HIV.
About three-quarters of all Aids-related deaths occur in Africa
The Joint United Nations Programme on HIV/Aids (UNAids) has said the number of HIV cases around the world now stands at 33.2m, compared with approximately 39m last year.
These latest figures appear to show a dramatic drop in cases. Almost 6m fewer people have HIV this year, it seems, compared with last year's figures.
But the UN officials involved in the report say that does not reflect reality.
The main reason for the fall, they say, is that they have adjusted their estimates after receiving more reliable data for some key countries.
The global prevalence - the percentage of people with HIV - has stayed roughly the same.
India accounts for about half of these apparently missing cases.
That is because there has been an intensive reassessment in the last 6 months of the numbers there.
Experts also think they have a better picture of the global epidemic as well.
There is more information, for example, about survival time - the average number of years someone with HIV will live without treatment.
That is now estimated to be up to 11 years.
Almost 7,000 people are newly infected with HIV every day - so the message is certainly not that the world can stop worrying about Aids
In countries which have a high rate of HIV, experts are now using household survey data, which also seems to give a more accurate picture.
So what does all this mean? Well, there is some positive news.
Experts say the number of new infections each year seemed to peak in the late 1990s and has declined since then.
There has also been a slight decline in the number of Aids-related deaths.
In some countries, prevention and treatment programmes do seem to have had an impact.
In Kenya, the Ivory Coast, Zimbabwe, Thailand and Cambodia, there seem to be signs of safer behaviour amongst people who are sexually active or who inject drugs.
But those gains have been off-set by other countries.
In Eastern Europe, the number of people with HIV has increased by 150% in the last 6 years - mostly in Ukraine and Russia.
In sub-Saharan Africa, the situation is still severe.
About two out of three people with HIV live in the region and about three-quarters of all Aids-related deaths are there.
So the message is certainly not that the world can stop worrying about Aids.
Almost 7,000 people are newly infected with HIV every day. Aids is still one of the biggest challenges facing global health.