Novelist and theoretical epidemiologist
Perhaps we are doomed - but it's unlikely that we'll be wiped out by some deadly disease. We still live in the shadow of events such as the 1918 influenza pandemic, which claimed over 50 million lives, but I don't believe that this sort of thing will happen again. In those days, there were many populations that had never encountered certain infectious agents, so their sudden arrival from different parts of the world could cause widespread mortality. This has changed - mainly because of air travel - so it is far less likely now that we will be completely vulnerable to an immigrant pathogen.
But air travel also increases the probability of a deadly bug arriving in the first place. A lot of time and money is invested in trying to determine what might be lurking in other species in some remote jungle, waiting to jump across and kill us in our comfortable homes.
What we must remember is that, each year, approximately 15 million people die of infectious diseases, some of which are preventable by vaccines and better sanitation and others for which we still have no vaccines. Rather than trying to hunt down and kill every infectious organism that could pose a threat to us, perhaps we should be spending our money on protecting the millions of people who are losing their lives to the diseases that are already with us.