In early November 2020, positive samples for yellow fever were reported from five Nigerian states. Nigeria is a high risk country for yellow fever and a priority country for the global strategy to eradicate yellow fever epidemics (EYE). The recurrence of the virus there in September 2017 was marked by outbreaks across the country.
The county has made great strides in improving yellow fever protection, vaccinating around 70 million people through reactive and preventive measures since 2017. However, given the ongoing COVID-19 measures, the country’s health system and human resources are under strain and responding to a challenge.
The World Health Organization (WHO) is helping Nigeria respond to the outbreak. As of December 3, and since the outbreak began, the country’s Center for Disease Control has reported a total of 530 suspected cases and 48 confirmed cases, with 172 suspected deaths occurring in the five affected states. Sample tests are currently being carried out in the country’s national reference laboratories.
Yellow fever is caused by a virus spread by the bite of infected Aedes and Haemogogus mosquitos. The mosquito bites of the Aedes aegypti type during the day. People who are infected can develop serious symptoms, including high fever, loss of appetite, nausea, muscle pain, headache, cramps, and jaundice. Some die from complications of internal bleeding and organ failure.
As the current outbreak began, epidemiologists and other health professionals have been deployed in each of the affected states. The investigation into the outbreak is being carried out by Rapid Response Teams (RRTs) under the coordination of the relevant state health ministries. Staff at selected hospitals in each of the five affected states were trained and provided with tools to treat yellow fever patients.
Dr. Onyinye Emefiene, WHO National Monitoring Officer / State Coordinator, leads one of the teams responding to the Delta State outbreak.
“When I got wind of the outbreak, the first reaction was to go straight to the Rapid Response Team to investigate the outbreak very early on a Saturday morning,” said Dr. Emefiene. “Since then, it has been a marathon to ensure that the active search for suspected cases is carried out, cases are properly managed, and reactive vaccination is started. Although reactive vaccination has been completed in the affected areas, the fight against the yellow fever epidemic in Delta State and beyond continues to contain and control struggles by strengthening our surveillance system and making effective vaccines available to all eligible individuals in the state. “
An accelerated mass preventive vaccination campaign against yellow fever was launched in the other counties of Delta state in the first week of December 2020. In the meantime, an awareness campaign is being carried out in the affected communities to avoid mosquito bites during the day, to keep the home environment clean and to eliminate mosquito breeding areas.
Yellow fever virus infection can easily be prevented with a vaccine that provides lifelong immunity. Large yellow fever epidemics occur when infected people introduce the virus into densely populated areas with high mosquito density and poor coverage for yellow fever vaccines. In Delta State, for example, there is no history of yellow fever vaccination in any of the cases, including a one-year-old baby.
Simultaneously with the outbreak, Nigeria’s COVID-19 response efforts have demanded an extraordinarily large amount of time and resources from the country’s health system, while lockdowns, travel restrictions and other measures to slow the spread have severely affected access to key health services.
National and state authorities are currently focused on responding to the COVID-19 pandemic, which limits the human resources required to conduct research and action to combat the yellow fever outbreak.
The relative proximity of the states of Delta, Enugu, Benue, and Ebonyi to Lagos is an additional problem, as the introduction of yellow fever outbreaks in urban settings with large unvaccinated populations can lead to rapid amplification with serious implications. Population movements that could contribute to the spread of the virus may have been reduced in the COVID-19 context. However, there is a lack of data and the risk of spread should be monitored.
Dr. Walter Kazadi Mulombo, WHO representative in Nigeria, said of the outbreak that the country is one of the high priority countries implementing the Yellow Fever Epidemic Elimination Strategy (EYE). Launched in 2017, the strategy includes more than 50 partners supporting 40 vulnerable countries in Africa and America to prevent, detect and respond to cases and outbreaks of yellow fever.
The partnership aims to protect vulnerable populations, prevent the virus from spreading internationally, and rapidly contain yellow fever outbreaks. The work carried out under this strategy is expected to protect more than 1 billion people from the disease by 2026. This strategy is steered by the WHO, Gavi, The Vaccine Alliance and the United Nations Children’s Fund (UNICEF).
This year, proactive vaccination campaigns were planned for most of the risk countries in Nigeria, including Delta. In total, over 31 million people are protected.
“As part of the EYE strategy, Nigeria has developed a 10-year strategic plan to eradicate yellow fever epidemics. Through this strategy, the country plans to vaccinate at least 80% of the target population in all states by 2026, ”said Dr. Mulombo.
34 countries in Africa and 13 countries in America are either endemic to or have regions endemic to yellow fever. Detecting yellow fever quickly and responding quickly through reactive vaccination campaigns are essential to fighting outbreaks. However, underreporting is a problem – the actual number of cases is estimated to be 10 to 250 times the number of currently reported cases.