People with Covid symptoms and those they live with should wear face masks at home, researchers have said, after a study found that just over half of people living with an infected individual also caught the virus.
According to research by the United States Centers for Disease Control and Prevention (CDC), the spread of the disease between people living in the same house is common and occurs soon after illness onset.
The research, published last week, also highlights that while children are less likely to become seriously ill with the disease, they have an important role in household transmission, with even those under 12 years old a risk to others.
Researchers said the findings reinforced the need for people who suspect they may have the disease to self isolate quickly.
“Because prompt isolation of persons with Covid-19 can reduce household transmission, persons who suspect that they might have Covid-19 should isolate, stay at home, and use a separate bedroom and bathroom if feasible,” the study authors wrote.
They added: “All household members, including the index patient, should start wearing a mask in the home, particularly in shared spaces where appropriate distancing is not possible.”
The report, part of an ongoing CDC-supported study, followed 101 people infected with Covid-19 and 191 of their household contacts in Nashville, Tennessee and Marshfield, Wisconsin, between April and September.
The study participants collected specimens – nasal swabs and/or saliva samples – every day for 14 days, as well as completing a symptom diary.
Over half of the people – 53 per cent – who lived with someone with Covid-19 became infected within a week, while three quarters of these secondary infections occurred within five days of the first symptoms in the initial patient.
Transmission of Covid-19 was as “frequent from either children or adults”, the researchers said.
“An important finding of this study is that fewer than one half of household members with confirmed SARS-CoV-2 [the virus which causes Covid-19] infections reported symptoms at the time infection was first detected,” the researchers said.
“Many reported no symptoms throughout seven days of follow-up, underscoring the potential for transmission from asymptomatic secondary contacts and the importance of quarantine.”
The household attack rate of 53 per cent is a higher figure than shown in previous studies. A study looking at household transmission in China, published in the BMJ Global Health earlier this year found a 23 per cent attack rate within the home.
In the CDC study, some 69 per cent of index patients – that is, those who were the first in the home to become infected – spent more than four hours in the same room with one or more household members the day before they became ill, while 40 per cent of these patients reported sleeping in the same room as someone else.
The importance of social distancing between people in the same household was emphasised by the UK government at the beginning of the pandemic but has been little promoted since.
In the summer public health experts writing in the BMJ said that people who are unable to self-isolate safely at home should be put up in special isolation facilities such as hotels and hostels, an approach adopted by countries including Italy, Finland and Lithuania.
They said that the UK’s Nightingale hospitals, set up in exhibition centres across the country during the first lockdown, could serve a similar purpose.
In China, field hospitals were set up to manage and strictly isolate patients with mild-to-moderate Covid-19, an approach that some believe may have contributed to the country’s control of the virus.
Paul Hunter, professor in medicine at the University of East Anglia, who was not involved in the CDC research, said it was a well conducted study that raised questions about the role of children, particularly those less than 12 years old, in the spread of the disease.
“This is an important observation as there has been debate about whether children are as infectious as others and has implications for the current debate about schools,” he said.
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