Human Cases of Rift Valley fever, South Africa, 2018

Following confirmation of a Rift Valley fever (RVF) outbreak in sheep on a farm in Jacobsdal area, Free State in May 2018 ( NICD web alert, 22 May 2018), human and vector surveillance was conducted on the affected farm by Provincial Department of Health and NICD. Mosquitoes collected on the affected farm tested negative for RVF virus, suggesting that active transmission had diminished due to decreased mosquito populations. Farmworkers and residents, who had been involved in the handling of potentially contaminated animal tissues during the sheep outbreak, were interviewed and sampled for RVF testing at NICD. Of 10 persons sampled, four individuals were retrospectively confirmed to have been infected with RVF virus; four individuals were shown to have probably been infected with RVFV, pending further tests on follow-up blood samples for confirmation; two individuals were not infected with RVFV despite handling potentially contaminated tissues. Six of the eight cases reported having experienced mild symptoms (fever, muscle pain, headache) in the preceding month, while none developed a severe disease that necessitated hospitalization. Healthcare workers must be aware of RVF and be vigilant for patients who meet the case definition and in such instances submit specimens to the NICD-NHLS for laboratory testing (Healthcare worker guidelines and Case Investigation Form).