An energy-efficient ventilation system is likely to be at the bottom of a serious coronavirus outbreak at a nursing home in Maassluis in June, an RIVM report related to the case suggests.

In total, 17 of the 21 residents of De Tweemaster nursing home and 18 staff were infected with coronavirus in the space of three days, despite staff wearing surgical masks. Six residents died.

The Volkskrant and current affairs programme Eenvandaag, which had access to  the report, quoted it as saying that a filter in the ventilation system and the air conditioning unit in one of the rooms contained virus particles. ‘The system in question is not connected to the other rooms in the home, the RIVM said, ‘and incoming as well as outgoing air is purified by filters’.

But according to ventilation expert Peter Uges, one of many who have been calling for an urgent review of ventilation systems, ‘contaminated air is simply pumped back into the rooms’.

‘The spaces must be ventilated with 100% outside air. It would be better to just open the windows,’ he told EenVandaag. He blamed the RIVM for not admitting aerosols – tiny droplets – are a proven way of spreading the virus, ac of ‘stubborness’.

The RIVM denied the Maassluis case had led to a revision of its ventilation guideline of July 28 saying it was based on international research. It will explain the ventilation issues more fully on Thursday at the press conference, a spokeman told broadcaster NOS.

Local Rotterdam health board GGD Rotterdam Rijnmond, which is also involved in the case, said in a reaction that the investigation is ongoing and that to point the finger at the ventilation system would be ‘premature’.

Autumn

The safety of ventilation systems is particularly important because autumn is approaching, making infections in closed spaces more likely. ‘If this is not tackled quickly there will be more outbreaks in homes,’ lung specialist Hans in ‘t Veen told the programme.

Schools too are at risk of more outbreaks because most have no mechanical ventilation systems and depend for fresh air on opening windows. ‘It’s questionable whether that will happen once it get colder,’ installations expert Wim Zeiler told the AD.

The air quality in 70% to 80% of classrooms in primary and secondary education is too high in carbondioxide, a sign that ‘ventilation is insufficient and air quality is substandard’, government body RVO said.

Secondary school council VO-Raad has said the issue is ‘raising concerns among schools, pupils and parents’. Both the council and teaching union CNV are calling for a recommendation on how to handle ventilation issues in schools from the Outbreak Management Team, and hope prime minister Rutte will announce a time frame for this to happen during Thursday’s press conference.