At the start of the coronavirus epidemic in the Netherlands, there was a high incidence of COVID-19 in the eastern part of the province of Noord-Brabant. The affected area overlapped the region where cases of Q fever were common from 2007 to 2010. The geographical overlap was noted during the first wave of COVID-19. For that reason, RIVM investigated whether people who previously had Q fever had an increased risk of contracting COVID-19, and whether they had a more serious course of illness from COVID-19.
RIVM investigated how often COVID-19 occurred during the early days of the coronavirus outbreak among people who previously had Q fever and lived in eastern Noord-Brabant. The number of cases that met these criteria was compared to the total number of people with COVID-19 in the same region. The research results confirmed that positive COVID-19 tests were in fact seen more often during the first wave among people living in eastern Noord-Brabant who previously had Q fever.
Influenced by testing policy during first wave
Many people who previously had Q fever still have one or more underlying health conditions. Some also have chronic Q fever or post Q-fever fatigue syndrome (QFS). As a result, they may have been tested for COVID-19 more frequently at the start of the epidemic. Testing capacity was limited at that point, and tests were primarily for people with underlying diseases and health conditions. The people in these groups were tested more often because they have a higher risk of severe illness from COVID-19. The coronavirus was probably also detected more often as a result of more frequent testing. From 1 June 2020 on, anyone in the Netherlands with symptoms could be tested, even if their symptoms were mild. After that policy shift, positive tests were no longer more common among people who previously had Q fever.
No indications of more serious illness
RIVM also examined whether people who previously had Q fever had a more serious course of illness from the coronavirus SARS-CoV-2. No indications of more serious illness were found in this study. Even among patients who were so ill that they needed to be rushed to a hospital emergency ward, COVID-19 did not lead to a more serious course of illness in people who previously had Q fever.
RIVM conducted the study in a joint research project with the Netherlands Institute for Health Services Research (Nivel), the Hart voor Brabant Municipal Public Health Service (GGD), Jeroen Bosch Hospital, and the Bernhoven hospital.
Air quality and COVID-19
Besides the geographical overlap with regions that had previously seen a high incidence of Q fever, there was also a geographical overlap with areas where air quality is poorer due to livestock farming. RIVM is also working with various partners to investigate whether there is any link between air quality and COVID-19 throughout the Netherlands. Various sources of air pollution are considered in the course of the research. RIVM expects to publish the results in 2023.
The full research results are presented in the RIVM report Study on Q fever and COVID-19. See also the news No evidence of more serious illness from COVID-19 among Q fever patients.