New WHO collaborating centre for understanding and detecting diphtheria

The Bavarian Health and Food Safety Authority in Germany, and its Centre for Diphtheria, has been designated as a WHO collaborating centre (WHO CC). In this capacity, the Authority will serve as a global reference centre, contributing to better understanding, control and prevention of the disease.

"We are proud of the potential this collaboration brings to our work, particularly in laboratory diagnostics, confirmation of diphtheria and pathogen characterization. We believe that the result will strengthen health systems in countries throughout the European Region and globally," explained Dr Mark Muscat, Technical Officer and focal person for diphtheria in the WHO European Region.

Nearly forgotten foe

Diphtheria was once among the most feared infectious diseases. It is caused by a bacterium that affects the upper respiratory tract causing respiratory diphtheria. It can also affect the skin causing ulcers, a condition known as cutaneous diphtheria. The most serious effect of the bacterium is its production of a toxin that damages the heart and nerves. Classic respiratory diphtheria today still has a mortality rate of 5-10% even with treatment.

The only effective way to control the disease is through vaccination starting in infancy with a 3-dose primary series followed by booster doses later in life. Thanks to high and sustained uptake of immunization across the WHO European Region, the incidence of diphtheria has declined dramatically in the past decades and the disease has become rare in many countries. However, persistent gaps in immunization coverage, and thereby an accumulation of susceptible individuals, create the opportunity for this and other vaccine-preventable diseases to resurface and spread.

Despite the overall decline in diphtheria incidence in recent decades, over 68 000 diphtheria cases were reported globally in 2018-2022. At the same time there has been a diminished capacity and expertise to diagnose the disease in countries, particularly where the disease has become uncommon. Limiting the spread and impact of outbreaks when they do occur requires rapid response including detection, diagnosis and treatment.

Adding value on a global scale

Housed within the Department of Public Health Microbiology of the Bavarian Health and Food Safety Authority, the Centre for Diphtheria performs diagnosis for all notifiable infectious diseases for Bavaria and functions as the German national reference laboratory for diphtheria and borreliosis (Lyme disease).

The Centre conducts whole genome-based molecular typing of isolates, which enables it to acquire a better understanding of the pathogen's properties including antibiotic resistance, molecular epidemiology and virulence. Part of its role in supporting WHO will be to participate in developing novel diagnostics and laboratory methods including antibiotic sensitivity testing and diphtheria toxin detection.

Together with the WHO CC for diphtheria based in the United Kingdom, the WHO CC in Germany will support WHO's work related to diphtheria on a global scale.

"Given the stakes with this deadly disease, we are very glad to be appointed as WHO CC in order to support WHO efforts in bringing knowledge about the disease and its diagnosis to the respective stake-holders in curative and preventive medicine, medical laboratories and the vaccination field," explained Professor Andreas Sing, Head of the Bavarian Health and Food Safety Authority.

The official launch of the Authority as a WHO CC will take place on 16 May 2024.

Improved management of diphtheria

The Centre for Diphtheria has made important strides in better understanding diphtheria and its epidemiology. In 2022, the Centre published a work on the detection and description of pan-European diphtheria outbreaks, leading to a rapid risk assessment by the European Centre for Disease Prevention and Control (ECDC) in October of that year.

The Centre also led research on potential zoonotic spread in various animal species found in the European Region, including pigs, water rats, hedgehogs, foxes and roe deer. The results identified isolated cases within Germany and showed that animals such as hedgehogs can, in fact, carry a close relative of the diphtheria pathogen found in humans.

In cooperation with the European Committee on Antimicrobial Susceptibility Testing (EUCAST), the Centre helped define a novel antibiotic resistance breakpoint for diphtheria. This dedicated research and enhanced understanding leads to improved management of the deadly disease and supports a vision for reduced mortality and increased vaccination among vulnerable groups throughout the European Region and across the globe.

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