EPIDEMIOLOGY

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The global prevalence of diphtheria has reduced dramatically due to comprehensive vaccine coverage; nonetheless, the disease remains widespread in many countries, although there are few reliable estimates of prevalence in these countries (Basak et. al 2015). 

A noteworthy feature of mass immunisation of diphtheria toxoid is that as the proportion of the population of protective levels of anti-toxin immunity (≥ 0.01 IU /ml) increases, the degree of exclusion of toxigenic strains from the population decreases (Saikia et. al 2010). 

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Until widespread immunisation of the U.S. population with diphtheria toxoid, diphtheria was usually children's disease. The introduction of the DTP vaccine programme has minimised childhood diphtheria in many countries. For example, during the first 13 years of the mass vaccination period (1919–1931), the confirmed cases of diphtheria decreased by 82.4% in the Netherlands. 

A major public health impact is triggered by timely vaccination. Studies showing that 72 % of children were given their first dose (at 2 months of age) of DTP in time, however only 59% (at 6 months of age) had received the third dose (DTP-3). Timely receipt, however, of scheduled vaccine dosages for urban Australian Indigenous children (Lodeiro et. al 2016).

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Focal diphtheria outbreaks are almost always linked to an immune carrier who has returned from an endemic area. In reality, recent outbreaks of clinical diphtheria have been associated with visitors from Russia and Eastern Europe in America and Europe (Lodeiro et. al 2016).

The WHO registered 16,611 cases in 2018 (Fig. 1). Diphtheria is commonly underreported in many regions like the countries of Asia, Africa and the eastern Mediterranean. In a number of countries, including Nigeria in 2011 and India during 2010–2016, outbreaks of respiratory diphtheria have been recorded. Highly vulnerable, as a result of the lack of availability of public-sector health facilities, are refugee resettlement centres (e.g. in theBangladeshi Rohingy refugee population). Estimated that approximately 76 % of refugees did not have long-term diphtheria security. Difference in Haiti, Venezuela and Yemen occurred during 2015-2018 due to the socio-economic crise or war which led to poor health and immunisation access. In endemic countries, the status of carriers of diphtheria is critical. A research conducted in India in 1989 on a reported case of C-carrying diphtheria. In~20% of children tested and 65% of species toxic is diphtheria. 

However, diphtheria carriers' status is much lower, even among people who have a poor immunisation or who drink alcohol, in non-endemic countries with optimal vaccine coverage (Page et al 2019).

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