Question: What is the most dangerous virus in the world?

Harriet Groom answered on 28 Jun 2012:

The most dangerous virus in the world is one that spreads easily (in the air), kills people very quickly and we don’t have a cure for. In science terms these are referred to as hazard group 4 viruses and have to be worked on with extreme caution. These viruses include Bolivian and Argentine hemorrhagic fevers, Marburg virus, Ebola virus, Lassa fever, Crimean-Congo hemorrhagic fever, smallpox, and various other hemorrhagic diseases.
Other viruses that are sometimes treated with this sort of caution are pandemic influenza like avian Flu.