Presence of SARS-CoV-2 on the hands of people including the high-touch surfaces acts as a route of transmission of the virus, according to a new study from the UK published in The Lancet Microbe. This study was conducted in the early phase of the pandemic during the alpha wave and pre-alpha wave.

This study was conducted prior to the alpha wave (from September to December 2020) and during the alpha wave (from December 2020 to April 2021). A total of 620 household contacts, symptomatic or asymptomatic, of newly diagnosed Covid patients were enrolled for the study. They underwent RT PCR testing for SARS-CoV-2 using nasal or throat swabs. Additionally, the hands of the index cases and that of the contacts were tested for the virus. Samples for testing were also collected from the frequently touched surfaces. Through this, the team of researchers from Imperial College London, the UK Health Security Agency (UKHSA) and the University of Oxford aimed to investigate if detection of the virus on the surfaces and hands could predict household transmission of SARS-CoV-2.

The household infection rate among the exposed contacts during the pre-alpha period of the pandemic was 28.4%, while during the alpha wave, the infection rate jumped to nearly 52%. While the viral load detected on nasal and throat swabs of the index cases did not correlate with transmission of the SARS-CoV-2, it did correlate with the presence of the viral RNA on their hands. The risk of infection among the contacts increased 1.7-folds if the virus was detected on the hands of the index cases compared to households where the index cases were negative for the virus on their hands with adjusted relative risk (aRR) of 1.70.

Detection of virus on ≥1 surface swabs also increased the risk of infection among the contacts by 1.6 times (aRR 1.66). Detection of virus on the hands of the contacts doubled their risk of infection with aRR of 2.06. A positive surface swab caused a 4-folds increase in the likelihood of positive hand swab (aRR 3.7). Six contacts who had initially tested negative on nasal and throat RT PCR, tested positive after samples from their hands and surfaces were positive for SARS-CoV-2 on RT PCR. On whole-genome sequencing, the virus from the hands of the contacts and nasal and throat swabs were similar.

This study is the first to show that presence of SARS-CoV-2 on the hands of patients and their contacts including the shared high-touch surfaces results in spread of Covid-19. It highlights the need for frequent handwashing and cleaning and disinfection of household surfaces.

Reference

1. Nieves Derqui, et al. Risk factors and vectors for SARS-CoV-2 household transmission: a prospective, longitudinal cohort study. Lancet Microbe. April 06, 2023. DOI:https://doi.org/10.1016/S2666-5247(23)00069-1