In Diagnostics, Virology

During the COVID-19 pandemic, there were significantly fewer infections with diarrhea-causing pathogens such as norovirus. However, with the relaxation of countermeasures against COVID-19, the number of norovirus infections appears to rise again, according to several studies. An overview.

Strict hygiene measures as well as the closing of schools, daycare centers, public facilities, restaurants and recreational facilities during the COVID-19 pandemic also reduced the spread of other viruses in 2020 and early 2021. Various studies indicate that cases of respiratory infections have declined during that time, as well as those of gastrointestinal infections:

  • The Department of Paediatric and Adolescent Medicine at Oslo University Hospital, Norway, reported a 74% decrease in gastroenteritis cases during the COVID-19 pandemic. Cases of viral pneumonia decreased by 89%, central nervous system infections decreased by 78%, and bronchiolitis cases decreased by as much as 90%. (source).
  • A study from France indicates a 67% decrease in gastroenteritis incidence during the COVID-19 pandemic compared to the pre-pandemic period. In addition, the incidence of bronchiolitis decreased by 79%, acute respiratory infections decreased by 49%, and chickenpox decreased by 90%. The incidence in children was affected the most. (source).

The spread of norovirus and other diarrhea-causing pathogens following the COVID-19 pandemic

For some time now, COVID-19 incidence has been declining in many places and most protective measures have been revoked. There is no comprehensive data available on the impact this has or will have on the incidence of viral diarrhea infections. While infections with norovirus and rotavirus are often subject to mandatory reporting, this is not the case for all diarrhea-causing pathogens. Therefore, there is less data available for other relevant pathogens, such as astrovirus and adenovirus. Nevertheless, an increase in diarrheal diseases caused by norovirus and other viruses has already been observed in several countries:

  • In its national norovirus and rotavirus bulletin, the UK Health Security Agency has reported that after a decline in norovirus and rotavirus infections during the COVID-19 pandemic, infection rates have increased again since mid-2021. In the 2021/2022 season, case numbers of norovirus infections were comparable to the pre-pandemic period, and for rotavirus infections, the numbers even were slightly higher (source).
  • According to a review of viral gastroenteritis cases caused by norovirus and rotavirus in Hong Kong, infection rates declined rapidly during the lockdown in the winter of 2019/2020, then increased again in the following winter (source).
  • A Spanish study observed an overall decrease of nearly 50% in the incidence of gastrointestinal infections with norovirus, adenovirus, rotavirus, astrovirus and sapovirus in under-5-year-old children during the COVID-19 pandemic in Madrid. With the relaxation of the measures in spring 2021, a moderate increase in infections has been observed (source).

These results show that a lot of infections have been prevented due to the countermeasures against COVID-19. Measures such as good hygiene remain important, even after the pandemic, and should not be neglected.

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