Viral Profile:

Tanapox

 

Background: Tanapox, a member of the Yatapoxvirus genus, was found in 1957 and 1962 epidemics where acute febrile illnesses were associated with localized skin lesions. The name of the virus comes from the fact that the epidemics occurred in individuals inhabiting the flood plains of the Tana River in Kenya. The virions are very similar to those of orthopoxviruses, however most of the virions are enveloped.

 

Incubation: The natural incubation period for tanapox is unknown, but in humans who have been intradermally inoculated with 100 infectious particles, erythema begins to appear by the fourth day.

 

Epidemiology: The virus is known to exist in Kenya and the DRC, but may also be in other parts of tropical Africa. Tanapox is spread through zoonosis, but neither its reservoir host nor transmission from animals to humans is known. However, it is known that there was a higher frequency of occurrence in those who worked or played close to the Zaire River than in those who hunted and worked on plantations. Both males and females of all age groups can be affected by this virus, but there does not yet seem to be any indication of person to person transmission even though cases have occurred in clusters. One method of transmission that seems possible is through arthropods biting monkeys or other reservoir hosts and passing it on to humans.

 

Symptomatology/Outcome: Symptoms include a mild fever before the appearance of lesions as well as possible severe headache and backache. The draining lymph nodes are tender and enlarged about five days after the first lesion appears. Lesions will initially start as nodules that resemble insect bites, but after two weeks may enlarge to be papules that are 15mm in diameter. The lesion will often be characterized as itchy, firm, cheesy, non-pustular nodules. By the third week, the lesions will ulcerate and at the end of five to six weeks, the lesions should have gradually healed and scarred. Most of the time there is only one lesion on an individual, but when there were multiple lesions, they seem to evolve and cluster together. Once an individual is infected, lifelong immunity occurs.

Prevention/Management: There are presently no known antiviral drugs that can effectively treat poxvirus infections. However, according to experimental data, cidofovir may provide some antiviral activity. Immunization with or exposure to other poxviruses will not prevent infection with the Tanapox virus. Transmission can be curbed through proper and effective control of arthropods since it is believed that arthropods are spreading the virus from reservoir hosts to humans. If the virus is transmitted through direct contact with a lesion, it might be best to bandage lesions to prevent their spread.

Knipe D.M., Howley P.M., Fields Virology Vol.2 4 th ed. Lippincott Williams &Wilkins. Philadelphia. 2001. pp2909-2911.

Dhar A.D., Werchniak A.E., Li Y., et al. “Tanapox Infection in a College Student.” NEJM. 350(4):361:366. Jan 22, 2004.

Peter J.B. “Tanapox Virus.” http://www.specialtylabs.com/books/display.asp?id=1914