No 4/7 - 2023

Continued increase in the number of infections with group A streptococci in Denmark

The level of infections caused by group A streptococci (GAS) remains high, including non-invasive infections like pharyngitis and wound infections and invasive infections (iGAS) like bacteraemia, meningitis and joint infections. Based on data extraction from the Danish Microbiology Database (MiBa), a total of 21 persons had iGAS detected in November 2022. This figure increased to 68 cases in December and climbed even further to 99 cases in January 2023. Currently, 3-4 new cases are detected daily.

The SSI has previously described the situation in EPI-NEWS no. 3/2023, which also presented a guideline for handling these infections in general practice. The development of the outbreak and genotyping results are available at the outbreak page, which is updated regularly (in Danish). The next update will be made on Friday 17 February.

It remains important for physicians to be attentive to the comprehensive transmission with GAS, which manifests, in particular, as pharyngitis and scarlet fever, but is currently also causing a number of invasive disease cases. Bacteraemia is the most frequently observed invasive manifestation in all age groups, but severe pneumonias, which spread to the pulmonary cavity and purulent joint infections are other frequently observed manifestations of invasive disease in children in the current outbreak in Denmark.

Those affected are still mainly the elderly, but children below five years of age have also been affected by invasive disease. The mortality among patients with invasive disease is in line with that recorded in the period leading up to November 2022. A limited number of deaths have been recorded among young children.

The risk factors for invasive disease are, among others, cardiovascular disease, diabetes, cancer and concurrent infection with influenza in particular or with chickenpox, but invasive GAS often affects persons with no known risk factors.

The SSI has assessed the available evidence of the effect of prophylaxis by use of antibiotics (PEP) among close contacts to patients with invasive GAS infections. The evidence is weak, mainly due to few published studies, but prophylactic treatment is provided for special risk groups in some countries. Based on the literature, the SSI cannot delimit special risk groups in which the advantages by giving antibiotic prophylaxis outweigh the potential drawbacks. Therefore, the question of preventive treatment needs to be considered in each case, taking into account the close contact’s age and any chronic diseases and immunodeficiencies. Normally, PEP will not be indicated for otherwise healthy contacts in case of either iGAS or GAS.

The SSI continuously performs whole-genome sequencing on invasive isolates submitted from all Danish departments of clinical microbiology. Analyses show that 53% of the invasive cases detected in January were caused by the type ST28/emm 1.0. A new sub-variant of ST28/emm 1.0 that has not previously been detected in Denmark comprises 34% of the cases and has been observed in all Danish areas. The new variant is characterised by the virulence factor speC; a super-antigen that is associated with scarlet fever and rheumatic fever, among others, and which in the current outbreak is associated with a small but significantly increased mortality.

(C. Munkstrup, P.H. Andersen, Department of Infectious Epidemiology and Prevention, T.B. Johannesen, Bioinformatics and Microbial Genetics, S. Hoffmann, Department of Bacteria, Parasites & Fungi)
15 February 2023