US must conduct 1.5M tests every day if it wants to come out of lockdown, warn experts

US must conduct 1.5M tests every day if it wants to come out of lockdown, warn experts
(Getty Images)

To reopen the American economy and remain that way, the US needs to test at least 500,000 people every day, warn researchers from Harvard. The analysis comes close on the heels of recently released guidelines by the Trump administration for reopening America in a phased manner.

Even though quarantine and stay-at-home measures reduce the spread of the virus, it does not change the underlying conditions that can allow COVID-19 to spread explosively if normal activities are resumed, say experts. To contain the virus and control the COVID-19 pandemic, countries need to know who is infected, and this will require a lot of testing, they add.

“All the evidence suggests that the number of cases will rise as social distancing is relaxed, even with rigorous testing and tracing. And so, we will likely need many more tests. We estimate that the number of tests needed every day is, at a minimum, 500,000. But, if we can’t be doing at least 500,000 tests a day by May 1, it is hard to see any way we can remain open,” says the research team from the Harvard Global Health Institute, Brigham and Women’s Hospital, and the Harvard TH Chan School of Public Health.

“If you want to have an open economy, you have to want ubiquitous, plentiful testing. Testing, tracing, and isolation are the pre-requisites for liberating the economy. Anyone who tells you that we don’t need large amounts of testing isn’t serious about controlling the disease, or serious about keeping the economy open,” says Dr Ashish Jha, faculty director of the Harvard Global Health Institute and KT Li Professor of Global Health at Harvard University.

The US has reported more than 759,690 cases and over 40,680 deaths in the COVID-19 pandemic as of April 20, according to the Johns Hopkins tracker. The research team says 20% of those tested for COVID-19 in the US get positive results. The World Health Organization (WHO) has said that to reopen, that number should be between 3% to 12%.

“We don’t know how many undiagnosed cases of COVID-19 there are in the US today because we have such limited testing capacity. We know that, on average, we’ve been identifying about 30,000 cases of COVID-19 every day through testing. We have been doing about 150,000 tests per day, meaning that our positive rate is about 20%. For context, in South Korea where testing has been extremely effective in limiting transmission, there is a 3% positive rate. In Germany and New Zealand, positive rates range from 6-8%,” says the team.

They add, “The WHO has suggested that an adequate test positive rate should be between 3 and 12%. A test positive rate above 10% likely reflects inadequate testing, meaning that testing should be increased to cast a wider net.”

According to researchers, 20% of those tested for COVID-19 in the US get positive results (Getty Images)

According to the US Centers for Disease Control and Prevention (CDC), public health, commercial and clinical laboratories are all testing for SARS-CoV-2, the virus that causes COVID-19, and reporting their results. The national percentage of respiratory specimens testing positive for SARS-CoV-2 increased from week 14 to week 15. In the case of public health laboratories, it increased from 17.3% during week 14 to 17.8% during week 15.

“For clinical laboratories, it increased from 10.6% during week 14 to 11.5% during week 15. In the case of commercial laboratories, the figure increased from 20.6% during week 14 to 22.6% during week 15,” says the CDC in its updates for week 15, ending April 11.

Summary of laboratory testing results reported to CDC (CDC)

The Harvard experts say that as of now, much of the testing in the US has focused on people with more severe symptoms. Mildly symptomatic people generally cannot get tests and asymptomatic people are not getting tested at all, they explain.

“Can we do what WHO and others have recommended — reach a 10% test positivity rate operating under the assumption that we are not missing too many cases? That would mean that today, we would need to be testing about 1.5 million people per day and by May 1, we may need to be testing only about 580,000 people per day. And, of course, the more we can test, the more we can be confident that we are capturing all the infected people in the US,” says the team in their analysis.

Even though stay-at-home measures slows disease transmission, it does not change the underlying conditions that can allow COVID-19 to spread explosively if normal activities are resumed, say experts (Getty Images)

The researchers, however, caution that there is no guarantee that a 10% positive rate will ensure most cases are being identified. Accordingly, they emphasize that the 500,000 tests per day recommendation is “probably too low.”

“We are likely substantially under-counting deaths and, therefore, the number of cases is likely higher. If, on the other hand, a case fatality rate of 1% is too high, that means there is a larger pool of asymptomatic individuals who are possible carriers of the coronavirus. Even if the case fatality rate is 0.8%, that adds a lot more cases. A 10% test positivity rate would miss a lot of infected folks,” says the team.

“Therefore, while we estimate that we should be testing between 500,000 and 600,000 people per day; this is clearly on the low side. We have, in trying to make these calculations, consistently tried to go low — make assumptions that lead us to need fewer tests. That’s why we are likely underestimating the number of tests needed,” they add.

Meanwhile, a report by the Johns Hopkins Center for Health Security also emphasizes that states should consider initiating the reopening process when the number of new cases has declined for at least 14 days; and rapid diagnostic testing capacity is sufficient to test, at minimum, all people with COVID-19 symptoms, including mild cases, as well as close contacts and those in essential roles.

It calls for sufficient public health capacity to conduct contact tracing for all new cases and their close contacts. The researchers caution that reopening can be considered only if the healthcare system can safely care for all patients, including providing appropriate personal protective equipment for healthcare workers.

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