Zika fever is an illness caused by the Zika virus, a member of the family Flaviviridae. The fever and virus are named after the Ugandan forest where the virus was first isolated. The virus is commonly found in Africa but has also been found in Malaysia and Micronesia, including Yap Island. Symptoms are similar to dengue fever, but are milder in form and usually last four to seven days. Hemorrhagic manifestations have been documented in only one instance, hematospermia (red–brown fluid in ejaculate). Common symptoms include a maculopapular skin rash that starts on the face or trunk before moving to the rest of the body, conjunctivitis, joint pain, low-grade fevers and headache. It is generally believed that the virus is spread by mosquitoes, making vector control an essential element to disease control. A single instance of sexual transmission of Zika virus between humans was reported in April, 2011 by a university biologist bitten by mosquitoes while performing research in Senegal who after returning to the US unknowingly transmitted the Zika virus to his wife by vaginal intercourse before he became symptomatic.