Wearing a mask indoors at home could help prevent the spreadof COVID-19 infection among family members living in the same household up to nearly 80%, but only before symptoms develop, suggests a study of Chinese families in Beijing, published in the journal ‘BMJ Global Health ‘.

This practice was 79% effective in stopping transmission before symptoms appeared.in the first infected person, but was not protective once symptoms developed, shows the study by researchers from the Beijing Center for Disease Prevention and Control and the Beijing Center for Preventive Medicine Research in China and the Institute Kirby, University of New South Wales, Australia

The World Health Organization (WHO)has not endorsed the use of face masks indoors or outdoorsconsidering that there is little good quality evidence for the measure to justify its recommendation.

Figures in China suggest that most person-to-person transmission of SARS-CoV-2, the coronavirus responsible for COVID-19 infection, has occurred in families. Butit is unclear whether the use of face masks could help curb domestic transmission rates, along with social distancing and disinfection.

To explore whether the masks could make a difference, the researchers questioned 460 people from 124 families in Beijing, China, abouthygiene and behavior of their homes during the pandemic.

Each family had at least one laboratory-confirmed case of COVID-19 infection between the end of February and the end of March 2020. The average family size was 4, but ranged from 2 to 9, and generally comprised three generations.

Family members were defined as those who had lived with the infected person for 4 days before andmore than 24 hours after that person’s symptoms appeared.

The researchers wanted to know what factors could increase or decrease the risk of contracting the virus later within the incubation period,14 days from the onset of symptomsof that person.

During this time, secondary transmission, spread from the first infected person to other family members, occurred in 41 of the 124 families.A total of 77 adults and children were infected in this waygiving an ‘attack rate’ of 23% or about 1 in 4.

About a third of the study children contracted the virus (36%; 13 of 36) compared tomore than two thirds of adults (just over 69.5%; 64 of 92).

Twelve of the children had mild symptoms; one had none.Most (83%) of adults had mild symptoms;in about 1 in 10 the symptoms were severe and one person became seriously ill.

The daily use of disinfectants,Opening windows and separating at least a meter were associated with a lower risk of transmitting the virus, even in homes with more people.

But the daily contact and the number of family members wearing a face mask after the onset of symptoms in the first person who developed themwere associated with increased risk.

Of all thebehavioral and hygiene factors,four were significantly associated with secondary transmission of the virus.

Diarrhea in the first person to become infected and close daily contact with themIncreased risk of transmitting the virus: Diarrhea was associated with a quadruple risk, while close daily contact, such as eating around a table or watching television together, was associated with an 18-fold increased risk.

Thefrequent use of bleach or disinfectants for household cleaningand wearing a face mask at home before symptoms appeared, even by the first person to have them, were associated with a reduced risk of viral transmission.

A face mask worn before symptoms started was79% effective, and 77% effective disinfection,to stop the transmission of the virus.

The authors suggest that the findings support the use of masks across the board, not only in public spaces, but also at home. ANDthe findings may also be relevant to families living with someone in quarantine or forced social isolation,and for the families of health workers who may face an ongoing risk of infection, they say.

“This study confirms that the highest risk of transmission in the home is before the onset of symptoms, but that precautions such as the use of masks, disinfection and social distancing in homescan prevent the transmission of COVID-19 during the pandemic, “Regardless of household size or overcrowding, they write.

“Transmission in the home is an important driver of epidemic growth”,they point out, adding that their findings could be used to “inform precautionary guidelines for families to reduce intra-family transmission in areas where there is high community transmission or other risk factors for COVID-19.”