4. Flaviviruses
These viruses often infect animals such as birds, or rats. They can also be carried and spread by ticks and mosquitos. While they can cause a lot of problems for animals, they can be harder on people. They can mutate and spread to humans easily.
While they all have their own symptoms and can cause a variety of problems, meningitis is one of the biggest risks. These viruses can appear as something mild such as the flu or a cold but quickly become worse. If they make their way to the bloodstream or into the spinal fluid, they can cause encephalitis and meningitis.
Since it takes so long for a person to show symptoms with these viruses, meningitis is often severe before a person seeks medical attention. Most of these viruses don’t have vaccines, so it’s almost impossible to avoid them. Luckily, they are somewhat rare and don’t cause serious problems in healthy people.