On 20 April 2020, WHO received information regarding a confirmed yellow fever case in Galangashie health area, located 30 km from Mango village, Oti district, Savanes region in the northern part of Togo.
The case is a 55-year-old woman with no vaccination history for yellow fever. She had onset of symptoms on 31 January 2020 and presented to a health facility on 3 February 2020 with fever and aches. The following day she developed jaundice and a blood sample was taken. On 7 February , the blood sample was transported to the national laboratory. On 10 February , the sample from the case was received at the national laboratory and test results on 17 March were Immunoglobulin M (IgM) positive for yellow fever. The positive yellow fever result was confirmed by the Institute Pasteur in Dakar Senegal, a yellow fever reference laboratory on 14 April 2020 by seroneutralisation.
On 22 March 2020, a multi-disciplinary investigation was conducted. 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 during active case finding in the community. The parents of the case reported that she was vaccinated in 2007; however no vaccination certificate is available. According to a survey conducted as part of the investigation, no additional cases of acute febrile jaundice were identified and 84% (132/157) of respondents reported previous yellow fever vaccination (through verbal recall and/or vaccination cards).
Togo has a robust febrile jaundice surveillance system, with weekly case reporting and sample testing. In 2019, 349 cases of febrile jaundice were reported and tested negative for yellow fever in the laboratory. All 44 health districts reported at least one case of febrile jaundice in 2019.
The last yellow fever outbreak in Togo occurred during late 2006 and early 2007, when three cases were reported from two adjacent districts: Dankpen district, Kara region and Oti district, Savanes region in the northern part of the country. In January 2007, two additional laboratory confirmed cases were reported: one from Kara region (Kozah district) and one from Maritime region (Lacs district). During preparation for the outbreak campaign, two additional laboratory confirmed cases were reported from Haho district. Following this outbreak, a national reactive vaccination campaign was conducted in 2007 and covered the entire country, targeting over 5.3 million people with over 102% reported administrative coverage.
From January to April 2020, 52 cases of febrile jaundice were reported, including one confirmed case of yellow fever in Oti district.
The yellow fever vaccine was introduced into routine immunization in January 2005. Yellow fever vaccination coverage in Togo is reported to be high (>85%), however, it is lower in the affected health area (Galangashie) (78% coverage in 2019). As a whole, Savanes region had a high coverage following the 2007 mass vaccination campaigns.
While immunity gaps may persist or have been introduced following population movements, there is a relatively high population immunity that has benefited from past vaccination activities and is anticipated to be protective against a widespread epidemic. This confirmed case illustrates that occasional yellow fever cases may occur in unvaccinated individuals due to sylvatic transmission, even in the context of high population immunity. This case underscores the importance of ensuring every person living in a high-risk area has lifelong protection afforded them by a single dose of yellow fever vaccine.
Public health responseA field investigation team was deployed on 22 March 2020. An epidemiological investigation has been conducted in Savanes region. Togo has rapidly mounted a targeted vaccination response and routine immunization strengthening on 14 May 2020, focusing on targeting the unvaccinated children in the affected area to ensure protection against yellow fever. The country plans to conduct an entomological survey in Savanes region.
WHO risk assessment
The detection of the yellow fever case in Savanes region shows that even in the context of relatively high population immunity there is a possibility of sylvatic yellow fever in unvaccinated people in rural areas. This highlights the importance of maintaining high population immunity in all high-risk areas for yellow fever. Recent entomological studies have indicated the presence of competent vectors, including the Aedes species, and the potential for spread to surrounding regions.The onset of the rainy season could increase the density of mosquito vectors, further exacerbating the risk of spread.
While mass immunization took place in Togo in 2007, the country is considered to be high risk for endemic transmission. Unvaccinated people remain vulnerable to yellow fever infection, particularly in rural areas.
Due to current COVID-19 pandemic, there is a risk of disruption to routine immunization activities due to both COVID-19 related burdens on the health system and a decreased demand for vaccination because of physical distancing requirements or community reluctance. A disruption of immunization services, even for brief periods, will result in increased numbers of susceptible individuals and raise the likelihood of outbreak-prone vaccine preventable diseases. As of 04 June 2020, there have been 452 confirmed cases of COVID-19 in Togo.
Togo is a high priority country for the Eliminate Yellow Fever Epidemic (EYE) strategy. In January 2005 the yellow fever vaccination was introduced into the routine immunization programme in Togo. Vaccination is the primary means for 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 Togo, from nine months of age. Togo also requires a yellow fever vaccination certificate for travellers aged nine months or older arriving from countries with risk of yellow fever transmission and for travellers having more than 12 hours of transit through an airport in a country with risk of yellow fever transmission.
Yellow fever vaccination is safe, highly effective and provides life-long protection. In accordance with the International Health Regulations (2005), Third edition, 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 is currently developing specific operational guidance for conducting mass vaccination campaigns in the COVID-19 context. When conditions permit, the EYE Strategy will support rapid resumption of preventive yellow fever vaccination activities according to WHO guidance.
WHO encourage 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 symptoms and signs and instructed to rapidly seek medical advice if experiencing signs and symptoms suggestive of yellow fever infection. Travellers returning to Togo who may be infected with possible high levels of the virus in the blood 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 Togo 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