Yellow fever pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Alejandro Lemor, M.D. [2]
Overview
Yellow fever is caused by a single-stranded RNA virus that belongs to the genus Flavivirus. Vectorborne transmission occurs via the bite of an infected mosquito, primarily Aedes or Haemagogusspp. Nonhuman and human primates are the main reservoirs of the virus, with anthroponotic (human-to-vector-to-human) transmission occurring. Humans infected with YFV experience the highest levels of viremia and can transmit the virus to mosquitoes shortly before onset of fever and for the first 3–5 days of illness. Given the high level of viremia, bloodborne transmission theoretically can occur via transfusion or needlesticks.
Pathophysiology
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- Yellow fever is caused by an arbovirus of the family Flaviviridae, a positive single-stranded RNA virus.
- Human infection begins after deposition of viral particles through the skin in infected arthropod saliva.
- The mosquitos involved are Aedes simpsaloni, A. africanus, and A. aegypti in Africa, the Haemagogus genus in South America, and the Sasbethes genera in France.
- Yellow fever is frequently severe but more moderate cases may occur as the result of previous infection by another flavivirus.
- After infection the virus first replicates locally, followed by transportation to the rest of the body via the lymphatic system.[1]
- Following systemic lymphatic infection the virus proceeds to establish itself throughout organ systems, including the heart, kidneys, adrenal glands, and the parenchyma of the liver; high viral loads are also present in the blood.
- Necrotic masses (Councilman bodies) appear in the cytoplasm of hepatocytes.,[2]
- There is a difference between disease outbreaks in rural or forest areas and in towns. Disease outbreaks in towns and non-native people are usually more serious.
Transmission
 Image obtained from CDC[3] |
- Yellow fever virus is an RNA virus that belongs to the genus Flavivirus.
- It is related to West Nile, St. Louis encephalitis, and Japanese encephalitis viruses.
- Yellow fever virus is transmitted to humans primarily through the bite of infected Aedes or Haemagogus species mosquitoes.
- Mosquitoes acquire the virus by feeding on infected primates (human or non-human) and then can transmit the virus to other primates (human or non-human).
- Humans infected with yellow fever virus are infectious to mosquitoes shortly before the onset of fever and for 3–5 days after onset.
- Yellow fever virus has three transmission cycles: jungle (sylvatic), intermediate (savannah), and urban.[3]
Jungle Cycle
- The jungle (sylvatic) cycle involves transmission of the virus between nonhuman primates (e.g., monkeys) and mosquito species found in the forest canopy.
- The virus is transmitted by mosquitoes from monkeys to humans when humans are visiting or working in the jungle.
Intermediate Cycle
- In Africa, an intermediate (savannah) cycle exists that involves transmission of virus from mosquitoes to humans living or working in jungle border areas.
- In this cycle, the virus can be transmitted from monkey to human or from human to human via mosquitoes.
Urban Cycle
- The urban cycle involves transmission of the virus between humans and urban mosquitoes, primarily Aedes aegypti.
- The virus is usually brought to the urban setting by a viremic human who was infected in the jungle or savannah.
References
- ↑ Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed. ed.). McGraw Hill. ISBN 0-8385-8529-9.
- ↑ Quaresma JA, Barros VL, Pagliari C, Fernandes ER, Guedes F, Takakura CF, Andrade HF Jr, Vasconcelos PF, Duarte MI (2006). "Revisiting the liver in human yellow fever: virus-induced apoptosis in hepatocytes associated with TGF-beta, TNF-alpha and NK cells activity". Virology. 345 (1): 22–30. PMID 16278000.
- ↑ 3.0 3.1 "CDC - Transmission of Yellow Fever Virus".