Yellow Fever

By Chioma Obinna

Nigeria maintains unenviable position as one of the countries with risk of yellow fever transmission. recording 364 suspected cases in 177 Local Government Areas, from 1st January to 3rd March 2019.

According to the Nigerian Centre for Disease Control, NCDC, since September 2017, all Nigerian states (36 + FCT) reported 4,100 suspected cases in 604 (78.0 percent) LGAs.

Of all suspected, probable and confirmed cases, 80 deaths were recorded with 29 deaths among confirmed cases.

Giving update of Yellow fever in the Weekly Epidemiology Report dated 25th February - 3rd March 2019, the NCDC, explained that the outbreak which has been active in Nigeria since September 2017 disclosed that between 1st January - 3rd March 2019, cases have been confirmed in 177 Local Government Areas of the country with four confirmed cases.

In the update of the Epi summary from NCDC's website, it was reported that Nigeria recorded 14 presumptive positives and one inconclusive case from four states in 10 LGAs, viz, Edo (8), Ondo (4), Kebbi (1) Imo (1) and the inconclusive case from Imo.

The Centre also reported that out of the five confirmed cases reported from 2019 samples which were sent to Institute Pasteur, Dakar, two were from Edo, another two from Ondo and one from Imo States. The report indicated that between 25th February and 3rd March 2019, 88 suspected cases were recorded and two new presumptive positive cases.

The Weekly Epidemiology Report also showed that; "The NCDC Central Public Health Laboratory (CPHL) reported two new presumptive positive cases from Edo State – 2 (Uhunmwode LGA), No new confirmed case from the Institute Pasteur Dakar. The last confirmed cases were 20th February 2019 and 18 States have recorded at least one confirmed case from Institute Pasteur Dakar since the onset of the outbreak in 2017,"

In the summary, the NCDC explained that from 2017 to 2018, 139 cases were confirmed in 17 States of Kwara (8), Kogi (10), Kano (1), Zamfara (19), Kebbi (7), Nasarawa (3), Niger (1), Katsina (2), Edo (69), Ekiti (2), Rivers (1), Anambra (1), FCT (10), Benue (1), Delta (1), Ondo (2) and Abia (1): in 46 Local Government Areas (LGAs).

Also, from September 2017 to December 2018, 276 samples (presumptive positive – 239 and inconclusive -37) were sent to IP Dakar for re-confirmation. All Nigerian states (36 + FCT) reported 4,100 suspected cases in 604 (78.0 percent) LGAs and of all suspected, probable and confirmed cases, 80 deaths were recorded with 29 deaths among confirmed cases.

The case fatality ratio (CFR) for all cases (suspected, probable and confirmed) is 2.0 per cent, and 21.0 per cent for confirmed cases.

Meanwhile, WHO says Nigeria is a high priority country for the Eliminate Yellow Fever Epidemic (EYE) strategy and planned a phased preventive Yellow fever vaccination campaigns to cover the entire country by 2024. Vaccination is the primary intervention for prevention and control of Yellow fever.

WHO has also recommended that vaccination against Yellow fever for all international travellers more than nine months of age coming into the country as there is evidence of persistent or periodic Yellow fever virus transmission.

The World Health Organisation, WHO, describes yellow fever as an acute viral haemorrhagic disease transmitted by infected Aedes mosquitoes and has the potential to spread rapidly and cause serious public health impact. Yellow fever is spread by the bite of infected Aedes aegypti mosquitoes. A mosquito becomes infected when it bites a person who has yellow fever in his or her blood. Direct spread of yellow fever from one person to another does not occur.

Currently, there is no specific treatment, although the disease is preventable using a single dose of yellow fever vaccine, which provides immunity for life. Supportive care to treat dehydration, respiratory failure and fever and antibiotic treatment for associated bacterial infections is recommended.

One of the reasons why Yellow fever is prevalent in the country is due to inadequate surveillance.

In a report, a researcher at the Nigeria Institute of Medical Research (NIMR), Yaba, Dr Abiodun Iwalokun, said the cycle of transmission of the fever must be broken.

Iwalokun, who heads the Immunology and Vaccinology Research Department of the Institute, stated: "We need to step up our vector surveillance patterns to determine first to stop yellow fever transmission before talking about elimination. "This can be done by breaking the transmission cycle and get an appreciable number of Nigerians vaccinated as well as encourage early detection," Iwalokun remarked.

On 23 October 1969, the Virus Research Laboratory of the University of Ibadan, Nigeria, was notified that cases of suspected yellow fever had occurred in the Jos area.

The diagnosis was confirmed by virus isolation and the existence of a widespread outbreak on the Jos Plateau and adjacent areas was established. This was the first recognized epidemic of yellow fever in Nigeria since 1953. Between September and the end of December 1969, an estimated total of 252 patients with yellow fever were hospitalised.

The case-fatality ratio for hospitalized patients was approximately 40 percent. The diagnosis of yellow fever was confirmed by virus isolation, serology, or pathology in 55 patients. It is estimated that up to 100 000 cases of yellow fever may have occurred during the epidemic.

VANGUARD