Report Type: Anticipatory Assessment
Location: South Africa
Disease Entity: Rift Valley Fever (RVF)
In six weeks, the Fédération
Internationale de Football Association (FIFA) World Cup championship
matches will be underway in various cities across South Africa. Current
estimates indicate approximately 375,000 foreign visitors are expected to
arrive in the region for the sporting event. At present, there is an active
Rift Valley Fever (FVF) outbreak in South Africa affecting both humans and
animals. The risk of infection to travelers to the country has been addressed
by both national and international health authorities. On April 20th, the Deputy Director of the South African
National Institute of Communicable Disease (NICD) made a public statement
indicating there is no risk of infection to visitors if contact with infected
farm animals and meat products is avoided. Similarly, on May 4th, the World
Health Organization (WHO) provided recommendations for safe travel noting that
individuals should avoid contact with animal tissue and animal products,
including blood, as well as avoiding the consumption of unpasteurized/uncooked
milk or raw meat. In addition, travelers are advised to protect themselves
against mosquito bites as Rift Valley Fever virus is vectored by a variety of
mosquito species including Aedes, Anopheles, Coquiletidia, Culex, Culicoides,
Erethmapodites and Mansonia, as well as by hematophagous flies. Heightened awareness of the biological risk situation in
South Africa came after RVF was confirmed in a 50-year-old female tourist
originating from Germany who visited Eastern Cape and Western Cape provinces of
South Africa in March and April. She developed symptoms on April 7th while in
Capt Town prior to her flight and arrival in Germany on April 8th. This is the
first recognized translocated case of RVF from an RVF-endemic country to a
temperate zone northern hemisphere country. To date, a total of 172 human cases, including 15 deaths,
have been documented in the provinces of Eastern Cape, Free State, Northern
Cape, North West and Western Cape. Infection has primarily occurred in farm
workers and veterinarians, as the virus has been transmitted to thousands of
domesticated animals resulting in illness. Praecipio International assesses: 1. The current level of risk to foreign visitors traveling
in South Africa to be negligible if precautions noted by the World Health
Organization are abided. 2. The risk to passengers on the flight from South Africa to
Germany to be negligible. 3. The risk for an RVF outbreak to occur is negligible in
the German community due to suboptimal temperatures to support mosquito-borne
transmission. Person to person transmission is negligible. In the healthcare
setting, risk of infection is also negligible if universal precautions are
observed. 4. The risk for triggering an outbreak in Cape Town is
negligible due to ambient temperatures currently falling below the range for
optimized mosquito biting activity and virus transmission competency. We have
received no report of RVF activity in Cape Town. 5. The already low risk for ongoing RVF activity in South
Africa continues to decline rapidly due to the abovementioned seasonal
conditions. According to 2008 statistics from the United States
Department of Transportation, direct non-stop air traffic from Johannesburg,
Cape Town, Durban, and Waterkloof, South Africa routes are active to and from:
This does not take into account indirect air flights.
South Africa’s environment is asynchronous from the United States, meaning the seasonal cycles are opposite. The period of concern would be at the overlap point where the potential for RVF activity is decreasing in South Africa while conditions to support RVF activity in the US are increasing. We are now exiting this overlap period.
Indigenous U.S. mosquitoes are competent to transmit RVF virus, and environmental temperatures are increasing, which contributes to increased mosquito counts, biting activity, and time for virus transmission competency (if the mosquito feeds on a viremic host).
However, the risk for
1. a traveler to become infected with RVF;
2. board an air craft bound for the US;
3. arrive in the US and be bit by a mosquito (which assumes levels of viremia in the host sufficient to ensure transfer of the virus to the mosquito);
4. and that mosquito bite cloven-hoofed animals or humans to trigger an localized outbreak is negligible.
The major concern regarding RVF is related to the agriculture industry and exposure of cloven-hoofed livestock, considered by some to represent a potential disaster. Detection and warning of an outbreak of RVF in the US, for example, would likely be delayed to the point where transmission and environmental presence of the virus would be pervasive enough to seriously compromise any containment strategy. It is questionable whether enough effective vaccine could be mobilized quickly enough to avert an epidemic and its associated high level of socio-economic disruption. If an epidemic occurs, the potential exists for permanent ecological establishment similar to what happened with West Nile virus in 1999.
In summary, we consider the risk of RVF translocation, subsequent epidemic triggering, and ecological establishment in the US to be negligible; however, the potential impact of such an event warrants awareness and careful monitoring of the situation.
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