Abstract

Each year, RIVM presents an overview of how many persons in the Netherlands got influenza and other respiratory infections. This year, the overview is dominated by the outbreak of the coronavirus SARS-CoV-2. The coronavirus dominated events in 2020 and 2021. As a result, in combination with the measures taken to prevent the spread of the virus, the number of persons who got other respiratory infections greatly decreased.

COVID-19
During the summer of 2020, from May through September, very few people tested positive for SARS-CoV-2. After the summer, the second period of infections began, which was characterised by two peaks: in October and at the end of December. This period started among the younger age groups (10 to 29 years old). Subsequently, increasing numbers of persons between the ages of 40 and 50 tested positive for SARS-CoV-2, followed by persons 70 years or older. The third period began in February 2021. At that time, the number of infections increased primarily due to the rise of the alpha variant, also known as the British variant. Between the beginning of February and the end of May 2021, this variant was the most frequently reported variant of the coronavirus.
Between 18 May 2020 and 23 May 2021, 1,584,237 persons tested positive for SARS-CoV-2, of whom 53,175 were admitted to the hospital and 9,649 were admitted to intensive care. 11,640 persons are known to have died as a result of COVID-19. During the second and third period, 14,739 more persons died in comparison to the average number of deaths during the same period over the last five years. This “excess mortality” is most probably related to the outbreak of the coronavirus.

Flu epidemic
During the flu season, hardly any persons were registered with influenza virus (2). There was therefore no flu epidemic this winter. This was probably due to the corona measures, which also help to prevent the spread of other viruses such as the influenza virus.

Notifiable respiratory infections
Some respiratory infections have to be reported to the Municipal Public Health Services. The Municipal Public Health Services can then intensively monitor infections and, if necessary, quickly take action to prevent their further spread. The number of reported cases of psittacosis (parrot fever) increased slightly in 2020 to 94, the highest number reported since 2010. In contrast, the numbers of reported cases of legionella (461), tuberculosis (623), and Q fever (7) have decreased in 2020. The decrease in number of legionella cases was probably due to reduced international travel in 2020. Q fever, psittacosis and legionella generally manifest themselves in the form of pneumonia. Persons with pneumonia are often not tested, so the causative pathogen remains unknown. The actual numbers are therefore higher than the reported numbers.