Rift Valley Fever Outbreak

INTERIM REPORT ON THE 2011 RIFT VALLEY FEVER(RFV)OUTBREAK IN SOUTH AFRICA
Data and information last updated: 20 May 2011

Report issued by:
The Outbreak Response Unit, Special Pathogens Unit, and South African Field Epidemiology and Laboratory Training Programme (SAFELTP), National Institute for Communicable Diseases (NICD) of the National Health Laboratory Service (NHLS). In collaboration with the South African Department of Health and Department of Agriculture, Forestry and Fisheries.

2011 case summary

 Sporadic human RVF infections have been detected in recent weeks (Figure 1) and we continue to encourage clinicians to collect specimens and complete a case investigation form (available on the NICD Website) for all cases meeting the suspected RVF case definition.    
 
From 1 January to 20 May 2011, we have identified a total of 32 laboratory-confirmed human RVF infections, with zero fatalities. The table and map (Figure 2) below provide an indication of the current geographical distribution of human infections. Most cases work regularly with animals within the farming (n=24, 75%), veterinary (n=4, 13%) or hunting (n=2, 6%) sectors. Prior to onset of illness, 81% (n=26) of cases report direct contact with infected animal tissue and/or body fluids, 59% (n=19) report mosquito bites, 22% (n=7) report acquisition and handling of meat not sourced from a retail outlet (i.e. informal slaughter), and 15% (n=5) report consuming unpasteurised milk.
 

 Number of laboratory-confirmed RVF cases and deaths by province,South Africa,2011
Province (Place exposed) cases Deaths
Eastern Cape 15 0
Free State 3 0
Gauteng 0 0
KwaZulu-Natal 0 0
Limpopo 0 0
Mpumalanga 0 0
Northern Cape 2 0
North West 0 0
Western Cape 12 0
Pending investigation (Free State / Western Cape) 0 0
South Africa Total 32 0

 2010 case summary
A total of 242 laboratory-confirmed human RVF cases with 26 deaths was identified in South Africa during 2010. Cases occurred from February to September 2010 (Figure) and ranged in age from 1 – 86 years (median 42.5 years). The majority (86%, 208/242) were male.  Of the 242 confirmed cases, data on occupation was available for 231 cases (95%). Of these, the majority (82%, 190/231) worked within occupations where direct contact with animals frequently occurs. Further history regarding exposure was obtained for 92% (218/242) of the total cases. Amongst these cases, 94% (205/218) reported a history of direct contact with RVF-infected ruminants prior to onset of symptoms, 3% (7/218) reported exposure to mosquitoes in the absence of direct animal/animal tissue or unpasteurised milk exposure, and 3% (6/218) re­port drinking unpasteurised milk but no direct con­tact with infected animals.


 
Figure 1: Epidemic curve illustrating the number of laboratory-confirmed RVF cases by epidemiological week of illness onset, by province, South Africa, last updated 20 May 2011 
 
Figure 2: Map Showing the number of laboratory-confirmed human RVF cases by administrative sub-district,South Africa,1 January 2011 to 20 May 2011