Sure, but as a method it's completely scattershot, and if that's where one is, one just isn't ready. I got dengue and a viral lung infection a few years ago, and the dengue at least actually put me in danger of death, and both felt like they were killing me. I live in India, it's easier to catch such diseases in this environment. There's dengue in our neighborhood again these days, it's carried by mosquitoes, and there are lots of mosquitoes now that the monsoon has begun. Two people in our apartment building have died of it. But it's nothing to count on.