CDC rewrites definition for coronavirus ‘close contact’

The leading US federal public health agency has rewritten its definition of who is at risk of contracting coronavirus to include people who come into close contact with infected individuals in multiple short bursts over a 24-hour period.

The new definition of “close contact” issued on Wednesday by the Centers for Disease Control and Prevention (CDC) will sharply expand the pool of those deemed in danger of being infected by the virus.

It will have implications for authorities carrying out contact tracing of those potentially infected by contagious individuals, and could lead to many more people being required to go into quarantine.

Under the old definition, “close contact” was defined as being within 6ft of an infected person over a solid block of 15 minutes or more. That has now been amended to cover a cumulative 15 minutes or more over a 24-hour period.

The change was made on the back of a study also released by the CDC on Wednesday that showed how the virus could be passed between individuals who were only in contact with each very briefly but on multiple occasions. The study was based on an incident at a prison in Vermont in August.

A male correctional officer came into contact with six detained individuals who were put into the quarantine unit at the facility. At that point the inmates were showing no symptoms and were awaiting test results for coronavirus.

Footage captured by prison surveillance cameras showed that the correctional officer only came within 6ft of the inmates for short periods of about a minute at a time. But when the exposure was counted up it exceeded a total of 15 cumulative minutes.

The six inmates all went on to test positive for the virus, and the officer later received a positive result as well even though he had come into contact with no other possible source of infection.

Announcing the new directive, the CDC said the findings underlined yet again the importance of wearing masks. The advice was all the more important, the agency said, at a time when the virus was on the ascendant across three-quarters of the country.

According to Johns Hopkins University, there have been 8.3 million confirmed cases in the US. The recorded US death toll now stands at 222,000.