Sylvatic

Because arthropod-borne viruses, or arboviruses, can be spread by competent mosquito vectors across great distances, they pose substantial risk to other regions in which the disease is currently nonendemic. Zoonotic arboviruses circulate in sylvatic and peridomestic cycles involving wild animals and nearby humans. Often these arboviruses remain undetected by health care systems. Kenya has had multiple arbovirus outbreaks in the past 2 decades resulting in economic and public health distress, including yellow fever, chikungunya fever, and Rift Valley fever.

Yellow fever has two transmission cycles, a sylvatic or jungle cycle and an urban cycle. The sylvatic cycle involving forest canopy mosquitoes as the vectors, and forest primates, mainly monkeys, as the hosts. The urban cycle involves Aedes aegypti as the vector and humans as the hosts. The urban cycle begins when humans become infected in the sylvatic cycle by entering forest habitats and being bitten by infected sylvatic vectors. People infected in this way return to their villages or cities, thereby initiating urban transmission... The oriental rat flea, "Xenopsylla cheopis", found on commensal rats in many parts of the world, is the most important vector of bubonic plague and murine typhus. The plague bacilli and murine typhus rickettsiae are ordinarily acquired by the flea during feeding on infected rats. Then the pathogens may be transmitted to humans in the absence of the flea's normal hosts, as when the rats are dying of plague in an epizootic. Plague exists in a sylvatic form in widespread parts of the world, and many of the 2,000 species of fleas are vectors of this disease.