South Africa faces wide outbreak of Rift Valley fever

Maryn McKenna

Mar 30, 2010 (CIDRAP News) – An outbreak of Rift Valley fever that began in South Africa in February has expanded to five of the country's nine provinces, with 63 human cases and 2 deaths in three provinces, according to national and international health agencies.

The outbreak is concentrated in the central province of Free State, where 54 of the 63 human cases and both of the fatalities resided, the South Africa Press Association reported Mar 27, citing national health officials. The human cases have been in farmers, farm workers, and veterinarians, the World Health Organization (WHO) said today. More than 70,000 animals have been vaccinated against the disease in Free State.

According to the World Organization for Animal Health, South African authorities have responded to 27 separate outbreaks in cattle, sheep, and goat herds, with 4% to 9% of herds falling ill and the case-fatality rates among animals ranging from 36% to 61% of those affected. The WHO said 78 farms had reported confirmed livestock cases as of yesterday.

Rift Valley fever is transmitted among animals by mosquitoes and passed to humans primarily through contact with the blood or organs of slaughtered animals carrying the disease. Most human cases are mild, with severe disease occurring in about 1% of cases.

In severe cases, the virus can cause meningoencephalitis, retinal disease, or bleeding, and there is no specific treatment, according to South Africa's National Institute for Communicable Disease (NICD).

The disease is primarily found in Africa. Disease experts are concerned about the possibility of an introduction of the virus into the United States; in recent years a US organization called the Rift Valley Fever Working Group has developed a research agenda and a response plan to address the threat.

South Africa is particularly alert to disease outbreaks at the moment, because the country will host the 2010 FIFA World Cup soccer tournament from June 11 to July 11 in venues around the country, including in Free State's capital, Bloemfontein.

South Africa has had sporadic cases of Rift Valley fever in recent years. The last major outbreak was in 1974-76, when an estimated 10,000 to 20,000 human cases occurred, the NICD said.

News editor Robert Roos contributed to this report.