On 30 August, the Ministry of Health in Niger notified WHO of unexplained deaths among humans, along with deaths in livestock in the Tahoua region of Niger. On 23 September, human and animal specimens were tested at the Institut Pasteur de Dakar (IPD) and were reported positive for Rift Valley Fever (RVF) virus by PCR and for specific IgM antibodies confirming the first outbreak of RVF in Niger. Initially the outbreak was centered in the north west of the country in areas bordering Mali, in particular around Tassara and Tchintabaraden in the Tahoua Region, however suspected cases of RVF have recently been identified in new areas to the north and south of Tchintabaraden.
The outbreak also coincided with the annual Cure Salée gathering in Ingall (close to Agadez), Tahoua region, where nomadic stockbreeders from Niger and surrounding countries gather with their animals. It is estimated that around 2 million cattle and smaller ruminants were in the affected area during the beginning of the outbreak. Furthermore, there were reports of waves of abortions and deaths among livestock in Boni-Bangou in Niger while human RVF suspected cases and animals were confirmed with specific IgM in the neighbouring region of Menaka in Mali.
From 8 August to 21 November, 266 suspected human cases including 32 deaths have been reported from Abalak, Keita, Madaoua, Tilia, Tassara, Tahoua department and Tchintabaraden in the Tahoua Region. From 8 August to 18 November, 196 specimens were tested and 17 patients were confirmed positive by RVF PCR and/or serological identification of IgM antibodies. Further testing of RVF negative specimens is being performed at IPD.
Given that more than 90% of the samples were tested negative for a recent RVF infection (IgG, PCR negative) and the increasing proportion of house wives and children affected there is a need to broaden the investigation to identify possible other underlying cause(s). In this regard an adapted investigation protocol is currently being developed which includes infectious and non-infectious diseases as well as chemicals and toxins.
Since October 2016, the epidemiological situation has evolved. Since August 2016, out of 196 specimen tested, only 17 patients have been confirmed with RVF, including 2 confirmed in November 2016 and 2 in October 2016. The epidemiological data are showing that the RVF outbreak amplitude is modest.
The spread of the RVF outbreak to previously unaffected areas should still be monitored as the health infrastructure is limited and the areas and populations dispersed along the stock routes.
The stockbreeder population is highly mobile and moves along stock routes to find pasture for their herds in the Sahel region that incorporates a number of neighboring countries. The RVF outbreak caused concern and posed a serious public health threat in Niger as the health infrastructure is limited and populations are dispersed along the stock routes. Surrounding countries previously considered at risk including Mali, Burkina Faso, Nigeria, Chad, Benin, Togo and Cameroon have not reported any RVF cases.