Eli5; how we find “patient zero” when there is disease outbreak? (Like how they found who started the ebola outbreak in 2014)

Question

Eli5; how we find “patient zero” when there is disease outbreak? (Like how they found who started the ebola outbreak in 2014)

In: 5171

Answer 1

The quick answer is that we don’t. The idea of patient zero is a misunderstanding that stems from the AIDS epidemic.

What people usually mean when they say patient zero though is the index case, which is the first documented case of an epidemic disease *within a population*. In other words, it’s not the person who started the pandemic or anything. That would be almost impossible to find out.

To find the index case though, you ask every known patient who they have had contact with in the time before they got sick, then you check if any of them have been sick and ask them the same question until you’ve found the common origin. Oftentimes there are more than one, especially with global pandemics like Covid.