WHO | Yellow fever – Togo

On April 20, 2020, the WHO received information on a confirmed case of yellow fever in the Galangashie health area, located 30 km from the village of Mango, Oti district, Savanes region in northern Togo.

The case is of a 55-year-old woman with no history of yellow fever vaccination. Symptoms appeared on January 31, 2020, and the health facility was presented on February 3, 2020 with fever and pain. The next day she developed jaundice and a blood sample was taken. On February 7, a blood sample was transported to a national laboratory. On February 10, a sample of the case was admitted to a national laboratory, and the results of the March 17 test were immunolobulin M (IgM) positive for yellow fever. The positive result of yellow fever was confirmed by seneutralization on April 14, 2020. The Pasteur Institute in Dakar Senegal, the reference laboratory of yellow fever.

On March 22, 2020, a multidisciplinary investigation was conducted. According to a field investigation report, the case did not have a recent pre-disease travel history, nor were additional cases found during the active case finding in the community. The parents of the case reported that she was vaccinated in 2007; however, a vaccination certificate is not available. According to the research conducted as part of the investigation, no additional cases of acute febrile jaundice were identified, and 84% (132/157) of respondents reported previous vaccination against yellow fever (via verbal recollection and / or vaccination card).

Togo has a solid monitoring system for febrile jaundice, 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 areas reported at least one case of febrile jaundice in 2019.

The last yellow fever epidemic in Togo occurred in late 2006 and early 2007, when three cases were reported from two neighboring counties: Dunkpen County, Kara Region and Oti County, Savanes Region in the northern part of the country. In January 2007, two additional laboratory-confirmed cases were reported: one from the Kara region (Kozah district) and one from the maritime region (Lacs district). In preparation for the epidemic campaign, two additional laboratory-confirmed cases were reported from Haho County. 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% of reported administrative coverage.

From January to April 2020, 52 cases of febrile jaundice were reported, including one confirmed case of yellow fever in Oti County.

The yellow fever vaccine was introduced into routine immunization in January 2005. The report that yellow fever vaccination coverage in Togo is high (> 85%) but lower in the affected health area (Galangashie) (coverage 78% in 2019), as on the whole, the Savanes region had high coverage after the 2007 mass vaccination campaigns.

Although differences in immunity may be maintained or introduced after population movements, there is a relatively high immunity of the population that has benefited from past vaccination activities and is assumed to protect against a wider epidemic. This confirmed case illustrates that occasional cases of yellow fever may occur in unvaccinated individuals due to sylvatia transmission, even in the context of high population immunity. This case underscores the importance of ensuring that every person living in a high-risk area provides lifelong protection with a single dose of yellow fever vaccine.

Public health response

• The field investigation team was deployed on March 22, 2020.
• An epidemiological study was conducted in the Savanes region.
• Togo quickly established a targeted response to vaccination and routinely boosted immunization on May 14, 2020, focusing on targeting unvaccinated children in the affected area to provide protection against yellow fever.
• The country plans to conduct entomological research in the Savanes region.

WHO risk assessment

The detection of a case of yellow fever in the Savanes region shows that even in a relatively relatively high immunity of the population there is a possibility of sylvatic yellow fever in unvaccinated people in rural areas. This emphasizes the importance of maintaining a high immunity of the population in all high-risk areas for yellow fever. Recent entomological studies have shown the presence of competent vectors, including Aedes species, and the potential for spread to surrounding areas. The onset of the rainy season can increase the mosquito vector density, further exacerbating the risk of spreading.

Although mass immunization took place in Togo in 2007, the country is considered to be at high risk of endemic transmission. Unvaccinated people are still susceptible to yellow fever infection, especially in rural areas.

Due to the current COVID-19 pandemic, there is a risk of interruption of routine immunization activities due to the health system burden associated with COVID-19 and reduced vaccination needs due to physical needs of distance or community reluctance. Discontinuation of immunization services, even briefly, will result in an increased number of susceptible individuals and increase the likelihood of diseases that can be prevented by vaccine outbreaks. As of June 4, 2020, 452 confirmed COVID-19 cases have been reported in Togo.

TKO advice

Togo is a high priority country for a strategy to eliminate the yellow fever epidemic (EYE). In January 2005, yellow fever vaccination was introduced into a routine immunization program in Togo. Vaccination is the basic means for the prevention and control of yellow fever. In urban centers, targeted vector control measures are also helpful to interrupt transmission. WHO and partners will continue to support local authorities in implementing these interventions to control the current epidemic.

The WHO recommends vaccination against yellow fever to all international travelers to Togo, as early as nine months. It also requires a yellow fever vaccination certificate for travelers aged nine months or older arriving from countries at risk of transmitting yellow fever and for travelers passing through an airport in a country at risk of transmitting yellow fever for more than 12 hours.

Yellow fever vaccination is safe, highly effective and provides lifelong protection. In accordance with the International Health Regulations (2005), third edition, the validity of an international certificate of vaccination against yellow fever extends to the life of the person vaccinated. An increased dose of yellow fever vaccine from international travelers cannot be required as a condition of entry.

The WHO has published guidelines for immunization activities during the COVID-19 pandemic and is currently developing specific operational guidelines for conducting mass vaccination campaigns in the context of COVID-19. When conditions allow, the EYE Strategy will support the rapid resumption of preventive vaccination activities against yellow fever WHO guidelines.

The WHO encourages its Member States to take all necessary actions to ensure that passengers are well informed about the risks and preventive measures, including vaccination. Travelers should also be aware of the symptoms and signs of yellow fever and instruct them to seek medical attention quickly if signs and symptoms suggestive of yellow fever infection appear. Travelers 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 a competent vector is present.

The WHO does not recommend any restrictions on travel and trade in Togo based on the data available on this epidemic.

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