The SARS-CoV-2 coronavirus spreads most easily through close contact between people indoors. At home, it is difficult to follow infection prevention measures, such as social distance. Therefore, family members who live together can potentially infect relatively easily from each other.
An earlier study showed that, on average, 16.6% of family members become infected from the first infected person. This coefficient is called the indicator of secondary infection, when calculating it, the period from the moment of infection of the first sick family member to his isolation is taken into account. Adults played a greater role in the transmission of infection than children; spouses most often infected each other.
In a new scientific work, American scientists have updated the data on the spread of coronavirus in families. They analyzed 87 studies that contained data on nearly 1.25 million family contacts of people infected with SARS-CoV-2.
The study showed that the rate of secondary exposure (the risk of infection in the family) increases over time. In the period from January to February 2020, it was 13.4%, and from June 2020 to March 2021, it was already 31.1%.
Scientists analyzed the factors that influence the risk of infection in the family:
- Adults became infected more often than children (29.9% versus 17.5%).
- The risk of infection is especially high among spouses (39.8%) compared to other family members (18.3%).
- Family members with concomitant diseases became infected more often than people without them (50% versus 22%).
- People with symptoms of COVID-19 were more likely to be infected than those who were asymptomatic or presymptomatic.
- In families where the infected person had only one contact, they became infected more often than with three or more contacts (35.5% versus 21.1%).
Scientists suggest that the increase in the rate of secondary damage could be due to improved diagnostics over time and changes in research methods. However, the emergence of more infectious variants of the coronavirus may have contributed.
The study authors recalled that vaccination can reduce the risk of contracting coronavirus in the family. They also indicate that the rate of secondary infection in the future may change depending on the characteristics of the new SARS-CoV-2 variants and vaccination coverage.