Question: How do epidemiologists pinpoint the origin of outbreaks of epidemics such as AIDS, Ebola, Swine Flu, and Cholera?

Wei Xun answered on 17 Jun 2011:

That’s a toughie! It’s very difficult to pin down the origin of these things, and as things move so fast, it’s quite common that the source is only found after the infections have peaked (ie reached the highest number of people infected), so in the end it’s not that useful anymore.

We have a system that links all the GPs and hospitals in the UK called “flagging”, any serious infectious diseases such as swine flu will be reported to a centre which is constantly watching what’s happening. With this system, you have the date and place of the infection. If there are other cases, you can use this info to draw a map of how the disease is spreading if you know how long it takes for someone to show symptoms from being infected. Once we know that we can try to stop the spreading such as giving people near the infected individual drugs like Tamiflu.

For something like AIDs that have been around for decades, the virus can be genetically tested to see if the strain matches any ones we already know about. I’m not sure how much use it is to find the origin of AIDs as it’s more important to stop people from catching it.

I really hope we won’t have to worry about Ebola in the future, it’s a really terrible infection.