event summary
This is an update on the Yellow Fever (YF) situation in the WHO African Region published on the Event Information Site (EIS) Announcement on December 8, 2021 and August 26, 2022.
In 2022, 12 countries in the WHO African region reported yellow fever outbreaks (Cameroon, Central African Republic (CAR), Chad, Côte d’Ivoire, Democratic Republic of the Congo (DRC), Ghana, Kenya, Niger, Nigeria, Republic Congo, Sierra Leone and Uganda). Eight of these countries experience continued transmission from 2021 (Cameroon, Central African Republic, Chad, Ivory Coast, DRC, Ghana, Nigeria, and Republic of Congo) and four countries report recently confirmed cases (Kenya, Niger, Sierra Leone and Uganda). One country, Gabon, reported cases in 2021, but no further cases were reported in 2022, indicating the end of the outbreak in Gabon.
From January 1, 2021 to December 19, 2022, a total of 203 confirmed cases and 252 probable cases with 40 deaths (CFR 9%) were reported to WHO from 13 countries in the WHO African Region, with an additional 49 plaque reduction neutralization tests (PRNT) positive samples currently pending classification.
Since August 5, 2022 (data included in the previous EIS), a total of 22 additional confirmed cases have been reported in ten countries: Cameroon (1), CAR (3), Chad (6), Ivory Coast (1 ), DRC (2), Ghana (1), Niger (4), Nigeria (2), Sierra Leone (1) and Uganda (1)). However, only seven confirmed cases developed symptoms after August 5, 2022 and were reported in four countries (RCA (2), Cameroon (1), Nigeria (2) and Niger (2), including one death in Niger). The remaining cases were retrospectively classified as confirmed (with symptom onset before August 5, 2022), based on confirmatory tests performed and details obtained from investigations.
Since 2021, 40 deaths (CFR 9%) have been reported out of the total of 455 confirmed and probable cases. Of those, 23 deaths have been reported among confirmed cases (CFR 11%) (Table 1). The high overall CFR among confirmed cases in 2021 (17 deaths, 11%) continued in 2022 (6 deaths, 12%), with several countries reporting CFRs greater than 1%.
The M:F ratio between confirmed cases was similar in 2021 and 2022 (1.3 and 1.6 respectively). The most affected age group among confirmed cases in 2021 was 10 years or younger; meanwhile, the most affected group in 2022 is 20 to 30 years old. Overall, about 71% of confirmed cases are 30 years of age or younger, and children 10 years of age and younger seem particularly affected.
The majority of confirmed cases in the two-year period were reported in the last quarter of 2021, with the majority from Ghana (62 cases, 12 deaths), Cameroon (35 cases, 0 deaths), Chad (30 cases, 5 deaths). ), Nigeria (24 cases, 0 deaths), and CAR (23 cases, 3 deaths). The other countries that have reported confirmed cases in the two-year period are Ivory Coast (8 cases, 0 deaths), DRC (6 cases, 1 death), Congo (4 cases, 0 deaths), Niger (4 cases, 1 death). death), Kenya (3 cases, 0 deaths), Uganda (2 cases, 0 deaths), Gabon (1 case, 0 deaths), and most recently Sierra Leone (1 case, 0 deaths). Countries such as Burkina Faso, Senegal, and Togo have reported probable cases that were later ruled out. A probable case from Benin is currently pending classification.
The M:F ratio between confirmed cases was similar in 2021 and 2022 (1.3 and 1.6 respectively). The most affected age group among confirmed cases in 2021 was 10 years or younger; meanwhile, the most affected group in 2022 is 20 to 30 years old. Overall, about 71% of confirmed cases are 30 years of age or younger, and children 10 years of age and younger seem particularly affected. Approximately 48% of the confirmed cases were in children and young adults <20 years, which is a higher burden than expected given that they were born after the implementation of YF in routine immunization in many of the affected countries.
Several of the recent confirmations have been from urban areas and/or locations with little or no underlying immunity (eg, near urban areas in Cameroon and Uganda; areas with no history of yellow fever vaccination such as Isiolo, Kenya). . Hard-to-reach and underserved populations have been disproportionately affected.
