Infectious Disease Epidemiology Annual Report - 2020

full report in German

The Infectious Disease Epidemiology Annual Report provides a summary and assessment of notifications of infectious diseases reported to the Robert Koch Institute (RKI).

The coronavirus disease (COVID-19) was the main notifiable infectious disease in 2020. The COVID-19 pandemic placed not only an enormous burden on the public health system in Germany, it has also affected the incidence and detection of other notifiable infectious diseases. In order to better understand the impact of the COVID-19 pandemic on other notifiable infectious diseases, chapter 4.4 presents further analyses of the difference between the expected number of cases and the actual number of cases for 2020.

Compared to the period before the COVID-19 pandemic, the number of cases of almost all notifiable infectious diseases reported in 2020 decreased substantially. The most notable reduction was observed for human to human communicable diseases. There were particularly large reductions in the number of cases for measles, whooping cough and invasive Haemophilus influenzae infections.

There was also a large reduction in gastrointestinal diseases. This was especially pronounced for rotavirus gastroenteritis, shigellosis and norovirus gastroenteritis.

Substantial changes were also observed for nosocomial infections, with particularly notable reductions for Acinetobacter spp. infection/colonisation with reduced carbapenem susceptibility. A reduction was also observed for sexually transmitted infections and blood-borne infections such as HIV infections.

Typical travel-related diseases such as dengue fever, malaria, typhoid fever as well as diseases such as Legionnaire’s disease, of which a proportion of cases in Germany tend to be acquired during travel, were also reported much less frequently.

Tick-borne encephalitis (TBE) was the only infectious disease that showed an increase in the number of cases reported.

The reasons for the reductions are complex and different for each disease and pathogen. Causality cannot be established by the reported data alone. In addition to an actual reduction in infectious diseases in the population, a number of factors relating to the COVID-19 pandemic may have led to the changes in the number of cases. Changes in the use of or access to healthcare services may play a role, but the public health measures taken to address the COVID-19 pandemic in particular, such as contact restrictions, distancing and hygiene rules as well as school and day-care centre closures and travel restrictions, may have led to a real change in the transmission dynamics of various infectious diseases.

The increase in TBE case numbers could be explained by changes in behaviours relating to leisure time, with many people tending to spend more time in nature. In addition, this increase could be linked to a larger tick population and a higher virus contamination rate of ticks than in previous years.

Despite the large decrease in the number of cases of influenza, chickenpox, the gastrointestinal diseases norovirus gastroenteritis, Campylobacter enteritis and rotavirus gastroenteritis, these infectious diseases continue to remain among the most frequently notified.

The reported influenza cases and data from the Working Group Influenza (AGI) sentinel for the 2019/20 season indicate a moderate influenza season. The influenza wave lasted a total duration of 11 weeks in 2020, which is shorter compared to previous seasons.

In addition, the COVID-19 pandemic and the emergence of variants of concern (VOC) at the end of 2020 also illustrate the increasing importance of integrated molecular surveillance. The results from sequencing are assessed together with the data from the mandatory notification system for infectious diseases. For example, genotyping of measles viruses is essential for estimating the length of transmission chains and is therefore a prerequisite for verifying the status of measles elimination in Germany. Sequencing also helped to identify several listeriosis outbreaks across federal states through foodborne outbreak investigations. By comparing the isolates from the affected individuals and from the contaminated food, the probable vehicle of the outbreak could be identified.

After the first mosquito-borne West Nile virus (WNV) infection in Germany in 2018, 5 infections were acquired in Germany in 2019 and a total of 20 in 2020 – presumably through mosquito bites. The virus is able to overwinter in Germany and is transmitted mainly by mosquitoes from the genus Culex, which are widespread in Germany. The epidemiological situation must continue to be closely monitored over the coming years.

The Infection Protection Act is regularly adapted to the changing epidemiological situation in Germany and internationally. According to § 7 IfSG, the detection of human pathogenic Borna disease viruses and Middle East respiratory syndrome-related coronavirus (MERS-CoV) have become notifiable pathogens and are now covered in new chapters in this Infectious Disease Epidemiology Annual Report 2020. Neisseria gonorrhoeae with reduced susceptibility to azithromycin, cefixime or ceftriaxone must now also be notified. These data have only been collected since March 2020 and are therefore not yet available for an entire annual period. They are therefore not yet reported in this annual report.