It is believed that the evolutionary origins of yellow fever most likely lie in Africa, with transmission of the disease from nonhuman primates to humans. Is a viral disease of typically short duration, which in most cases, symptoms include fever, chills, loss of appetite, nausea, muscle pains particularly in the back, and headaches. The disease is caused by the yellow fever virus and is spread by the bite of an infected female mosquito. Symptoms typically improve within five days but sometimes the fever comes back, abdominal pain occurs, and liver damage begins causing yellow skin.
West Nile Virus
This is a single-stranded virus that causes West Nile fever, a viral infection. It is primarily transmitted through mosquitoes but there been cases where ticks have been found to carry the virus as well. First detected in 1937, it’s detected through blood tests. In most cases of infections people have few or no symptoms, in less cases, they develop a fever, headache, vomiting, or a rash, while in fewer scenarios encephalitis or meningitis occurs.