As the US struggles to contain surging caseloads and an increasing death toll from the virus, the Food and Drug Administration (FDA) on Saturday issued its first emergency approval for a testing approach that allows samples from multiple people to be combined for much faster tracking of new infections.

The agency gave so-called emergency use authorisation to Quest Diagnostics to test combined samples from up to four people — a method known as pooled testing. If the pooled test is negative, then all four are in the clear. If it is positive, then each sample would be individually tested to determine who was infected.

The decades-old method has been used to test for the virus in China, Germany, Israel and Thailand. In Nebraska, a state scientist found a loophole that allowed him to circumvent federal prohibitions on the method.

The US military has used the technique for diseases at its bases worldwide since it first tested for syphilis in the 1940s.

This approach expands the number of people who can be tested without requiring the use of additional crucial materials and staffing.

“Sample pooling becomes especially important as infection rates decline and we begin testing larger portions of the population,” FDA chief Stephen Hahn said.

The number of weekly tests reported nationwide has increased to more than five million in early July from about one million in early April, according to data collected by the Covid Tracking Project. At the same time, the rate of positive tests, which had steadily declined from late April to early June, has been increasing in recent weeks, the data show.

The federal action to speed testing came as at least two states, Arizona and North Carolina, announced single-day records on Saturday.