Wearing masks at home may curb COVID-19 spread within family

Wearing masks at home can prevent COVID-19 from spreading among family members, especially before symptoms appear, suggests a study.

“It informs universal face mask use and social distancing, not just in public spaces, but inside the household with members at risk of getting infected,” the researchers highlighted. 

“Given epidemic growth is dominated by household transmission … this further supports universal face mask use, and also provides guidance on risk reduction for families living with someone in quarantine or isolation, and families of health workers, who may face ongoing risk,” they added.

When at least one member within the household (primary case or family contacts) wore a face mask before the primary case developed COVID-19 symptoms, the disease was five times less likely to spread among household members (odds ratio [OR], 0.21, 95 percent confidence interval [CI], 0.06–0.79). [BMJ Glob Health 2020;5:e002794]

The protective benefit of mask wearing was seen regardless of the household size or crowding.

In addition, regular use of ethanol or chlorine-based disinfectants was associated with a 77 percent significant reduction in household transmission (OR, 0.23, 95 percent CI, 0.07-0.84).

“This study confirms the highest risk of household transmission being prior to symptom onset, but that precautionary [non-pharmaceutical interventions], such as mask use, disinfection and social distancing in households can prevent COVID-19 transmission during the pandemic,” according to the researchers.

Following symptom onset, the risk of secondary transmission within the household was also lower when all members wore masks compared with households whereby no one did (OR, 0.20, 95 percent CI, 0.07–0.60).

Participants in the retrospective cohort study were 335 people from families with at least one COVID-19 case. The rate of secondary transmission within household was 23.0 percent.

The researchers also looked at the characteristics and hygiene practices of household members to identify possible predictors of secondary transmission.

As expected, one major factor associated with an increased risk of household transmission was close contact — frequently being in close contact with the primary case daily raised the risk of transmission by 18 times (OR, 18.26, 95 percent CI, 3.93–84.79).

Also, the risk of household transmission was fourfold greater if diarrhoea was present in the primary case (OR, 4.10, 95 percent CI, 1.08–15.60).

“Many people with infection are required to self-isolate at home, where their household contacts will be at risk of infection,” pointed out the researchers. “We show that non-pharmaceutical interventions are effective at preventing transmission, even in homes that are crowded and small.”

Nonetheless, there is practical difficulty in applying universal wearing of face mask at home, the authors acknowledged, saying there is “no necessity for everyone to wear masks at home.”

“We recommended those families with members who were at risk of getting infected with SARS-CoV-2 (such as ever having contact with a COVID-19 patient, medical workers caring for COVID-19 patient, or having history of travelling to high-risk areas) [to don on a face mask at home to prevent the disease from spreading],” they urged.