People who live in the same household as people who tested positive for COVID-19 had a 17% chance of becoming infected themselves, a new study found.
The hallmark of global efforts to halt the spread of coronavirus disease 2019 (COVID-19) has been so-called social distancing, which public health officials say will stop the spread of the disease by limiting contacts between people.
However, such efforts leave one particular group vulnerable: the family members of people unknowingly infected with SARS-CoV-2.
In a paper published in Clinical Infectious Disease, investigators in China report on infection rates among people living in the same house as people who tested positive for the virus. The results show that overall, the rate of infection among household members was 16.3%, with adults facing a greater likelihood of infection than children.
The findings suggest quarantining infected patients can help to limit its spread within the household.
Corresponding author Jianying Chen, of Huazhong University of Science and Technology, calculated the findings based on a study of 105 index patients who tested positive for COVID-19 and 392 people who lived in the same homes as the index patients. The enrollees were tracked using medical records and phone interviews. The index patients were all treated at one of 2 hospitals, each more than 100 kilometers from Wuhan.
Each of the index patients had either visited Wuhan recently or had had exposure to people from Wuhan or other high-risk sites within 14 days of the onset of symptoms. The study took place between January 1 and February 20.
At the start of the study, household contacts were enrolled as non-infected if they had no symptoms and had received at least 2 negative tests for COVID-19. Those family contacts were isolated for 14 days, monitored by healthcare workers, and periodically tested for the virus.
After 2 weeks, 64 of the 392 household contacts had tested positive for COVID-19. Of those, the median age was 45. Thirty-three of the patients were male, and all but 4 were over the age of 18. That meant children had a 4% secondary attack rate, and adults had a 17.1% secondary attack rate.
One reason for the high rate among adults might lie in the fact that, investigators noted, spouses of infected patients were more prone to secondary attack than other household members. They hypothesized this might be due to spouses spending more time with each other than with other household members.
Though the overall rate means the vast majority of household contacts did not get infected, Chen and colleagues note that the secondary infection rate they calculated is higher than the rates found for other coronavirus diseases, Severe Acute Respiratory Syndromes (SARS), and Middle East Respiratory Syndrome (MERS). The rate is also higher than the rate observed in the 2009 influenza A pandemic.
The investigators also looked at the impacts of self-quarantining within the home. Fourteen of the 105 index cases involved patients who isolated themselves away from other household members immediately at the onset of symptoms and before tests confirmed infection. Chen and colleagues noted that none of the people living in the same homes as those 14 patients became infected.
“This indicated that home quarantine by themselves since onset of symptoms might make certain sense to prevent the transmission of SARS-CoV-2 in [the] household,” Chen and colleagues write.
However, the investigators cautioned that the sample size was small, so it’s difficult to know for sure whether or not the results would hold true on a larger scale.