Indoor, high-occupancy and poorly ventilated spaces present an increased risk of Covid-19 transmission, the State’s health watchdog has warned.
This is particularly the case where “shouting and singing” and prolonged contact occurs, or where face-coverings are insufficiently used, the Health Information and Quality Authority says.
To reduce risk, targeted public health measures are needed in settings where “super-spreading” events are likely to occur, it advises.
Hiqa also found most virus clusters occur in household settings, and so household members are at a high risk of becoming infected if a Covid-19 case is present.
“The international evidence highlights that the main factors that contribute to spread of Covid-19 are indoor settings, crowds, and prolonged contact with others,” according to Dr Máirín Ryan, director of health technology assessment and deputy chief executive. “Much can be done to mitigate risk in these settings, such as ensuring good ventilation and people following public health advice to use face coverings, keep physical distance and wash their hands frequently.”
In its advice to the National Public Health Emergency Team, the watchdog says there is “consistent evidence” that clusters most commonly occur in household settings, and that there is a higher rate of onward transmission in households, compared with other settings.
Other settings where large numbers of clusters have been consistently observed include nursing homes, hospitals, meat and food processing plants, large shared accommodation, sporting activities, bars, nightclubs and restaurants, gyms, offices, shopping centres, cruise ships, weddings, shopping malls, prisons, mines and religious settings.
Superspreading
It says many of these settings have been associated with “superspreading events”, where infection is transmitted to large numbers of people.
Activities involving “dining, drinking, exercising, singing or shouting, and prolonged face-to-face conversation, especially in indoor crowded environments” were associated with an increased risk of transmission in studies.
And while risks are substantially lower outdoors, clusters in outdoor environments have been observed, particularly when there are large gatherings, limited social distancing, dense congregation, and mixing among groups.
Other factors increasing the risk in workplaces include working despite symptoms; higher proportions of people from lower socio-economic groups, ethnic minorities and migrant groups; lack of personal protective equipment or handwashing facilities; and exposure to tools.
The reports says that although schools may potentially be regarded as high-risk settings, this was not reflected in the Irish data, with relatively few clusters (2 per cent of the total).
As time progresses, a different picture of where clusters occur may emerge, Hiqa says, particularly given the measures taken to provide protection in high-risk settings.
