Final report GGD: role of ventilation in nursing home outbreak remains unclear

How could 17 residents of the Tweemaster care facility in Maassluis be infected with the coronavirus? According to the Municipal Health Service (GGD), this was probably caused by an infected resident and infected employees. There were questions about the role played by the ventilation system. Research by the GGD shows that both cases may have played a role.

residents and 18 of the 34 employees were infected in a short period of time. Six residents died.

The outbreak is under a magnifying glass because a low concentration of virus particles was found in the ventilation system. According to microbiologist Peter de Man, this led to infections and the RIVM dismissed that conclusion. But according to the GGD there are no hard conclusions to draw as to whether the ventilation led to infections in the Tweemaster.

Continuing to work with minor complaints

The most obvious explanation is that persons got covid-19 through mutual contact, the researchers write. “During the investigation we saw that one of the residents had the virus and that it was discovered late,” says Ewout Fanoy, infectious disease physician of the Rotterdam-Rijnmond Municipal Health Service (GGD).

“In this nursing home, residents in the corridors and in living rooms have contact with each other, and this infected resident also walked around there. When this resident tested positive, it was decided to keep wards separate.”

Well, they wore a nose mask when there was contact with residents, but they took that off during breaks and they didn’t keep a foot and a half distance from each other. Fanoy: “That’s a lesson for the coming winter months, that everyone should keep their distance from each other, even on the shop floor and during breaks”

Virus particles in ventilation system

The examination cannot give a definite answer about the extent to which the ventilation systems played a role in the contamination in the care institution, says Fanoy. Insufficient ventilation remains one of the possible routes of infection, the researchers write in the GGD report. But an important note is that there is still a great deal of uncertainty about the role of aerosols.

“In this study, virus particles were found on ventilation grilles in a living room where the automatic system did not bring in enough fresh air. We cannot rule out the role of ventilation in buildings.”

The RIVM noted earlier that it is possible to be exposed to the coronavirus via small breathing droplets that can remain stuck in non-ventilated spaces. Fanoy: “It is important to include this scenario in follow-up research in case of new outbreaks, then you can hire technical people to improve the ventilation.”