Transmissibility of Severe Acute Respiratory Syndrome Coronavirus 2
Among Household Contacts of Coronavirus Disease 2019-positive Patients:
A Community-Based Study in India
Abstract
Background: The transmission of severe acute respiratory syndrome
coronavirus 2 (SARS-CoV-2) is complex and multifactorial. We aimed to
identify the risk factors for infection among the household contacts of
index patients and to determine the incubation period, serial interval,
and estimates of secondary infection rate. Methods: We conducted a study
in three districts of Kerala among the inhabitants of households of
reverse transcriptase polymerase chain reaction (RT-PCR)-positive
coronavirus disease (COVID-19) patients between January and July 2021.
COVID-19-positive patients and corresponding contacts were enrolled and
followed up for 28 days to determine RT-PCR positivity and the presence
of total antibodies against SARS-CoV-2 on days 1, 7, 14, and 28 from the
date of enrolment. Results: The mean incubation period, serial interval,
and generation time were 1.6, 3, and 3.9 days, respectively. The
secondary infection rate was 43.0%. Individuals who worked outside the
home were protected, whereas those who had kissed the COVID-19-positive
patients during illness were more than twice at risk of infection than
those who had not kissed the COVID-19-positive patients. Similarly, the
contacts who had shared a toilet with the COVID-19-positive patients
were more at risk than those who had not shared a toilet. However, the
contacts who reported using masks were at a higher risk of infection in
household settings. Conclusions Assessment of SARS-CoV-2 transmission in
household settings is important, considering its high secondary
infection rate. Close physical contact and toilet sharing increase the
risk of infection. This study demonstrates shorter incubation period and
serial interval.