In 2016, the number of whooping cough cases has reached a worrying record in Germany – 22,000 lab confirmed cases were reported to the Robert-Koch-Institute (RKI). In the previous year there were 14,000 cases and more than 1,500 patients have already been registered in 2017 (as of February 9th, 2017).
Whooping cough is caused by bacteria called Bordetella pertussis which proliferate within the mucosa of the respiratory tract and affects it. The cough is highly contagious and transmitted by droplet infection. The most typical sign are coughing bouts potentially leading to vomitus and lasting for several weeks.
Preventing whooping cough, closing vaccination gap
Severe complications, e.g. pneumonia, may particularly occur in infants younger than 6 months. The Standing Committee on Vaccination therefore recommends vaccinating children as soon as possible (from the third month). Basic immunisation requires 5 inoculations until the 14th month of life, and further boosters in childhood and adolescence. Also adults are encouraged to get vaccinated against Pertussis every ten years. This recommendation is primarily addressed to persons working in any health service, women of childbearing age, as well as people who are in close contact with a newborn baby. Pregnant women may also be vaccinated, if no immunisation but an infection risk exists (read also: Infections during pregnancy – health risks for the unborn child). Vaccination gaps in adolescents and adults are thought to be one of the major causes of the current increase of whooping cough cases.
Since immunity against Bordetella pertussis does not last lifelong, neither vaccination nor a past infection allow to exclude whooping cough during diagnostics if the clinical picture is suspicious. In addition to the clinical findings, confirmation by laboratory diagnostics is recommended.
Diagnostics and reporting obligation of whooping cough
In the initial phase of the disease, the bacteria may be directly detected in mucosal specimen by cultural or molecular methods. Specific antibodies are synthesized after one to three weeks and can be determined by ELISA. The RKI recommends using ELISA applying Pertussis toxin (PT) as antigenic target which is most specific for this bacterial species. An elevated titer of anti-PT IgG or a documented titer increase between two samples taken with a time difference of a few weeks indicate an existing Pertussis infection. Although anti-PT IgA are known to be little sensitive, they are highly specific and may also be determined during laboratory diagnostics. Determination of specific IgM is not recommended since the antibodies have little informative value.
Direct detection of the bacteria as well as any positive serological finding have been obligate to register in Germany since 2013.