Asymptomatic transmission of covid-19

December 21, 2020

BMJ

Allyson M Pollock, professor of public health1, James Lancaster, independent researcher

What we know, and what we don’t

The UK’s £100bn “Operation Moonshot” to roll out mass testing for covid-19 to cities and universities around the country raises two key questions. How infectious are people who test positive but have no symptoms? And, what is their contribution to transmission of live virus?

A cluster randomised trial of cloth masks compared with medical masks in healthcare workers

C Raina MacIntyre1, Holly Seale1, Tham Chi Dung2, Nguyen Tran Hien2, Phan Thi Nga2, Abrar Ahmad Chughtai1, Bayzidur Rahman1, Dominic E Dwyer3, Quanyi Wang4

Objective The aim of this study was to compare the efficacy of cloth masks to medical masks in hospital healthcare workers (HCWs). The null hypothesis is that there is no difference between medical masks and cloth masks.

Setting 14 secondary-level/tertiary-level hospitals in Hanoi, Vietnam.

Participants 1607 hospital HCWs aged ≥18 years working full-time in selected high-risk wards.

Intervention Hospital wards were randomised to: medical masks, cloth masks or a control group (usual practice, which included mask wearing). Participants used the mask on every shift for 4 consecutive weeks.