On 15 April 2020, WHO received information regarding a confirmed case of yellow fever in Magandi village, Tchibanga city in Nyanga Province of southern Gabon, 590 km from the capital, Libreville.
The case is an 83-year-old male with no known vaccination history for yellow fever. He had onset of symptoms on 30 January 2020 and presented to a health facility on 2 February 2020 with abdominal pain and jaundice. Between 2 February and 9 April, he consulted the Urban Health Centre in Tchibanga, the Christian Alliance Hospital in Bongolo and the University hospital in the capital Libreville where the case received anti-malarial treatment and remained hospitalized until his death on 9 April 2020. On 14 April 2020, the laboratory results received from the WHO Regional Reference Laboratory at the Institute Pasteur in Dakar, Senegal, confirmed yellow fever infection, by seroneutralisation test. The additional differential diagnostic tests performed were negative for dengue, West Nile fever, chikungunya, Crimean-Congo Haemorrhagic fever, Zika and Rift Valley fever.
On 15 April 2020, a multi-disciplinary investigation was conducted in Tchibanga by the Ministry of Health (MoH) with technical support from WHO. According to the field investigation report, the case had no recent travel history prior to the onset of illness and no additional cases were found in the community despite extensive case finding activities.
The last cases of yellow fever in Gabon were detected in 2019. These two confirmed cases of yellow fever were in unvaccinated international workers in the health district of Mitzic, Woleu-Ntem Region.
The yellow fever vaccine was introduced into routine immunization in 2000. Yellow fever vaccination coverage in Gabon is reported to be suboptimal (less than 85%) (WHO/UNICEF estimates, 2018). The case is from Mongo health area, where vaccination coverage is 76% in 2020.
Public health responseA field investigation team was deployed on 15 April 2020. An epidemiological investigation was conducted in the case’s village of residence. Enhanced routine immunization is being planned. An entomological survey is being planned.
WHO risk assessment
Yellow fever is an acute viral haemorrhagic disease that has the potential to spread rapidly and cause serious public health impact in unvaccinated populations.
The detection of the confirmed case of yellow fever in Nyanga Province shows the possibility of spill-over of sylvatic yellow fever in endemic areas to unvaccinated people in a rural area even in the context of moderately high population immunity (70%). This highlights the importance of achieving and maintaining high population immunity in all high-risk areas for yellow fever.
There is currently a risk of disruption to routine immunization activities due to COVID-19 related impacts on the health system and a decreased demand for immunization due to physical distancing requirements or community reluctance. Disruption of immunization services, even for brief periods, will increase the numbers of susceptible people and the likelihood of outbreaks of vaccine preventable diseases. As of 12 June 2020, there have been 3,463 confirmed cases of COVID-19 in Gabon.
Gabon is a high priority country for the Eliminate Yellow Fever Epidemic (EYE) strategy. Vaccination is the primary intervention for the prevention and control of yellow fever. In urban centres, targeted vector control measures are also helpful to interrupt transmission. WHO and partners will continue to support local authorities to implement these interventions to control the current outbreak.
WHO recommends vaccination against yellow fever for all international travellers to Gabon, from nine months of age.
Yellow fever vaccination is safe, highly effective and provides life-long protection. In accordance with the International Health Regulations (2005), the validity of the international certificate of vaccination against yellow fever extends to the life of the person vaccinated. A booster dose of yellow fever vaccine cannot be required of international travellers as a condition of entry.
WHO has published guiding principles for immunization activities during the COVID-19 pandemic and has developed specific operational guidance for conducting mass vaccination campaigns in the COVID-19 context. The EYE Strategy will support rapid resumption of preventive yellow fever activities according to WHO guidance.
WHO encourages its Member States to take all actions necessary to keep travellers well informed of risks and preventive measures, including vaccination. Travellers should also be made aware of yellow fever signs and symptoms and instructed to rapidly seek medical advice if experiencing signs and symptoms suggestive of yellow fever infection. Travellers returning to Gabon who may be infected with yellow fever may pose a risk for the establishment of local cycles of yellow fever transmission in areas where the competent vector is present.
WHO does not recommend any restrictions on travel and trade to Gabon on the basis of the information available on this outbreak.
For more information on yellow fever:WHO yellow fever fact sheet WHO strategy for yellow fever epidemic preparedness and response WHO list of countries with vaccination requirements and recommendations for international travellers A Global strategy to Eliminate Yellow Fever Epidemics (EYE) 2017-2026, WHO 2018, Guiding principles for immunization activities during the COVID-19 pandemic A Global Strategy to Eliminate Yellow Fever Epidemics (EYE), document for SAGE – 26 September 2016 Framework for decision-making: implementation of mass vaccination campaigns in the context of COVID-19