Global Epidemiology of Diphtheria, 2000-20171

Abstract

In 2017, a total of 8,819 cases of diphtheria were reported worldwide, the most since 2004. However, recent diphtheria epidemiology has not been well described. We analyzed incidence data and data from the literature to describe diphtheria epidemiology. World Health Organization surveillance data were 81% complete; completeness varied by region, indicating underreporting. As national diphtheria-tetanus-pertussis (DTP) 3 coverage increased, the proportion of case-patients <15 years of age decreased, indicating increased protection of young children. In countries with higher case counts, 66% of case-patients were unvaccinated and 63% were <15 years of age. In countries with sporadic cases, 32% of case-patients were unvaccinated and 66% were >15 years of age, consistent with waning vaccine immunity. Global DTP3 coverage is suboptimal. Attaining high DTP3 coverage and implementing recommended booster doses are necessary to decrease diphtheria incidence. Collection and use of data on subnational and booster dose coverage, enhanced laboratory capacity, and case-based surveillance would improve data quality.

Keywords: Corynebacterium diphtheria; bacteria; data quality; diphtheria; epidemiology; global; public health surveillance.

Figure 1

Cases of diphtheria as reported to the World Health Organization and the United Nations Children’s Fund, through the Joint Reporting Form, worldwide, 1980−2017.

Figure 2

Percentage (number) of countries reporting each diphtheria vaccination schedule, 2018. The number after the plus sign indicates the number of booster doses on the national schedule after the 3-dose primary series and before the age of 18 years.

Figure 3

Reported cases of diphtheria per Joint Reporting Form, by World Health Organization region and worldwide, 2000−2017.

Figure 4

Vaccination status of diphtheria cases in higher case count versus sporadic incidence countries (full dataset, 34 countries), 2000–2017.

Figure 5

Proportion of diphtheria case-patients <15 years and >15 years of age in higher case count versus sporadic incidence countries (full dataset, 34 countries), 2000–2017.

Figure 6

Percentage of diphtheria case-patients >15 years of age, by national DTP3 coverage, 2000–2017. Each circle represents a country, and its size is proportionate to the average number of cases reported from the country per year of data in the dataset. The largest data point represents a large number of cases in a single year among Rohingya refugees from Myanmar. The vaccination coverage of the Rohingya population is unknown; therefore, the average of DTP3 coverage of Rakhine State in Myanmar from 2016–2017 was used (18). DTP3, diphtheria–tetanus–pertussis vaccine; UNICEF, United Nations Children’s Fund; WHO, World Health Organization.