Rift Valley Fever

I recently returned from Tanzania having spent two weeks in Arusha. The headline in the Arusha Times the day after we arrived read “Fear grips town as Rift Valley Fever spreads.” The article described fear surrounding the outbreak of Rift Valley fever that had spread through Kenya and was then suspected in Arusha and surrounding areas. Had I not understood how Rift Valley Fever is spread, I may have been alarmed, as many of the residents in Arusha were. Because of the outbreak, the prices of chicken and fish became prohibitive for many people, and butchers could not give away their beef. Goat meat was even less desired, because the first two reported deaths resulting from Rift Valley fever in Tanzania were supposedly related to goat meat.

Rift Valley fever is caused by the Rift Valley virus, named for the Rift Valley of Kenya where it was first isolated in 1930. The Rift Valley fever virus (RVF virus) is a member of the Bunyaviridae family of viruses (RVF virus, Hantaan virus, Dugbe virus and Bunyamwera virus).

Rift Valley fever primarily affects livestock and can cause disease in a large number of domestic animals including cattle, sheet, goats, and camels. RVF is spread by infected mosquitos and other biting insects (animal-to-animal, animal-to-human and human-to-human). Rift Valley fever is also occasionally transmitted to humans through contact with blood, body fluids or tissues of infected animals (veterinarians, slaughter-house workers, etc.).

The risk of RVF infection associated with eating beef, goat or any other animal that may be infected with the virus is minimal, especially if the meat is properly cooked. It would seem that the fear that has affected the eating habits of residents and livelihood of numerous people associated with the meat industry is largely unwarranted.

Rift Valley fever periodically occurs in sub-Saharan Africa, but has also occurred in Egypt, the Arabian Peninsula, and Madagascar (see Map).

The outbreak of Rift Valley fever that began last fall in Kenya is believed to be on the decline. RVF has occurred in the North Eastern, Coast, Eastern, Central and Rift Valley Provinces of Kenya. As of January 30, 2007, 411 suspected cases were reported, including 121 deaths.

An outbreak of Rift Valley fever has also been reported in Somalia. As of January 30, 2007, 100 suspected cases were reported in Somalia, including 48 deaths.

Symptoms associated with RVF are mild for most people infected: fever, generalized weakness, back pain, and dizziness lasting 2-7 days. However, some patients progress to a severe hemorrhagic fever, encephalitis or ocular disease.

The risk of acquiring Rift Valley fever when traveling to an outbreak area is relative to the risk of exposure to mosquitos carrying the virus from infected animals. As there is no licensed preventive vaccine currently available, prevention involves avoiding contact with mosquitos and other blood-sucking insects! See aritcles under "related content" below for precautions against mosquito-borne diseases.

Related content:

Travel-associated dengue.

Mosquito-borne disease prevention.

Sources:

Rift Valley Fever in Kenya and Somalia - update 3 (WHO).

Update on Rift Valley Fever in Kenya and Somalia (CDC).

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