Diphtheria – Nigeria

13 September 2023

Situation at a glance

Since epidemiological week 26, ending 2 July 2023, Nigeria has recorded an unusual increase in cases of diphtheria across several states. From 30 June to 31 August 2023, a total of 5898 suspected cases were reported from 59 Local Government Areas (LGAs) in 11 states. In week 34 (ending 27 August 2023), 234 suspected cases have been reported from 20 LGAs in five states, with one Lab confirmed case1 from the 22 samples collected. Eighteen of these cases were epidemiologically linked 2 and 141 were classified as clinically compatible.

Diphtheria is a highly contagious vaccine-preventable disease caused mainly by the bacteria Corynebacterium diphtheriae which can be fatal in 5-10% of cases, with a higher mortality rate in young children.

WHOs most recent risk assessment of the diphtheria outbreak in Nigeria has maintained the risk as high at the national level, and low at the regional and global levels. Public health measures such as vaccination response, enhanced surveillance for early case detection, case management and risk communication coordinated by the Nigeria Centre for Disease Control (NCDC), in collaboration with WHO and other partners, are being implemented in response to the outbreak.

Description of the situation

Since the last Disease Outbreak News on diphtheria in Nigeria was published on 27 April 2023, the country has reported suspected cases of diphtheria weekly to WHO. However, between 30 June and 31 August 2023, Nigeria recorded an unusual increase in the number of confirmed diphtheria cases(figure 1). From 30 June to 31 August 2023, a total of 5898 suspected cases were reported from 59 LGAs in 11 states across the country. The majority (99.4%) of suspected cases were reported from Kano (1816), Katsina (234), Yobe (158), Bauchi (79), Kaduna (45) and Borno (33). 

Of the cumulative 8353 suspected cases reported since the outbreak was first reported in 2022, 4717 (56.5%) cases were confirmed4 (lab confirmed1 (169; 3.6%), epidemiologically linked2 (117; 2.5%) and clinical compatibility3 (4431; 93.9%)). While 1857 (22.2%) were discarded as not compatible with diphtheria, 1048 (12.5%) cases are pending classification and 731 (8.8%) cases had unknown diagnosis. The case fatality ratio dropped slightly from 6.7% during the last update to 6.1%. Of the 4717 confirmed cases, 3466 (73.5%) were aged 1 – 14 years, of these 699 were aged 0-4 years, 1505 aged 5-9 years, 1262 (aged 10 – 14 years. More than half of the cases (2656; 56.3%) were females. Only 1074 (22.8%) of the confirmed cases were fully vaccinated against diphtheria, 299 (6.3%) were partially vaccinated. More than half of the cases (2801; 59.4%) were unvaccinated.      

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