On 14 September 2017, the Nigeria Centre for Disease Control (NCDC) informed WHO of a confirmed case of yellow fever in Kwara State. On 15 September, an official notification as per the International Health Regulations (IHR) (2005) was issued by the Nigerian National IHR Focal Point.
The case-patient was a 7 year-old girl from Kwara State who developed symptoms on 16 August 2017 including fever, vomiting and abdominal pain. She had no previous history of yellow fever vaccination and no travel history outside of the state in the two years prior to illness onset. Her blood sample tested positive by Polymerase Chain Reaction (PCR) at the Lagos University Teaching Hospital, and confirmed by serology tests performed at the regional reference laboratory, Institut Pasteur de Dakar (IPD).
From 2 July through 19 December 2017, 341 suspected cases of yellow fever have been reported from 16 states, including Abia, Anambra, Borno, Edo, Enugu, Kano, Katsina, Kogi, Kwara, Kebbi, Lagos, Nasarawa, Niger, Oyo, Plateau, and Zamfara states. Six states have reported confirmed cases of yellow fever (Kano, Kebbi, Kogi, Kwara, Nasarawa and Zamfara).
As of 19 December, a total of 213 samples have been tested in five laboratories in Nigeria. Of these 213 samples, the Nigerian laboratories tested 63 samples positive for yellow fever and there was one inconclusive result. Of 63 samples sent to IPD for laboratory confirmation of yellow fever infection, 32 were positive, 24 were negative, and 7 results are pending at the time of publication of this update.
Of the 341 suspected cases, 214 (62.8%) are males. The most affected age group is people aged 20 years and younger who account for 65.9% of cases. The total number of deaths (among suspected, probable and confirmed cases) is 45 and nine among the confirmed cases. The case fatality rate for all cases (including suspected, probable and confirmed) is 21.1% and 28.1% for confirmed cases. Further epidemiological investigations are underway.