Yellow fever is a mosquito borne viral disease. It was the first human virus to be isolated and identified, although the condition was identified by the 17th century. Once endemic in the southern United States, eradication efforts against the mosquito vectors have made it very rare in North America. However, it is still endemic in many tropical countries and vaccination is recommended when travelling, as is taking precautions to avoid mosquito bites. It still causes 200,000 infections and 30,000 deaths per year, primarily in Africa. Unfortunately, due to increasing urbanization, the number of infections has been increasing since the 1980s.
The condition's initial symptoms are prosaic - fever, chills, nausea, lack of appetite and muscle pain. In most patients, these symptoms self-resolve in about five days. However, in about 15% of patients, the symptoms return in about one day and progress to bleeding (including bloody black vomit), abdominal pain and liver damage, resulting in the jaundice that gives the condition its name. This phase is life-threatening and requires intensive care until the condition resolves itself. If the disease continues to progress, it causes death by cytokine storm, shock and multiple organ failure.
The condition is difficult to identify as it's symptoms are similar to other diseases from malaria to Ebola. Although it can be identified by a careful differential diagnosis, only specialized tests are definitive, and often take days or weeks to get a confirmatory result. Any patient suspected to have yellow fever should be quarantined to prevent a larger outbreak.
In American history, Dr. Samuel Mudd, who had been imprisoned in Florida for his part in the assassination of President Abraham Lincoln, was pardoned four years later after he helped to deal with a severe prison outbreak.