Washington (AFP)

Before lifting the containment measures imposed since March in the United States, experts repeat that it is necessary to set up a massive screening of the new coronavirus in order to be able to monitor its resurgence and react more quickly if necessary.

"Our testing system is great," said Donald Trump on Tuesday. "The country's testing capacity is dangerously insufficient," said Democratic Leader of the Opposition in the Senate, Chuck Schumer.

Here is an overview of screening in the country, which on Wednesday counted more than 600,000 confirmed cases and 27,000 deaths from Covid-19.

- The number -

The United States has performed 3.1 million tests to date, according to the Covid Tracking Project. The number really started to soar in late March, and is currently increasing by around a million a week.

In absolute numbers, it is much more than any other country. Italians are about a million tests done, South Korea 500,000 cases tested, according to Our World in Data, which compiles data for the planet, with a warning that statistics are often incomplete and inaccurate : some figures concern the number of tests, others the number of cases (a person can be tested several times, or with two samples each time). For the United States, this varies from state to state.

Everything changes when you relate to the population, the United States being populated by 329 million inhabitants. Italians and South Koreans proportionately tested more people: around 18 and 10 per 1,000 inhabitants, respectively, compared to 9 per 1,000 in the United States.

The Icelanders, a small country of 364,000 inhabitants, are even far ahead with 100 per 1,000 inhabitants (10%) tested.

- Capabilities -

The tests were carried out until the end of February only in Atlanta, at the headquarters of the Centers for Disease Control (CDC), which had developed their own diagnostic test but missed the production of tests intended for public laboratories in each of the states.

On February 29, the United States government authorized private laboratories to perform their own tests. But these laboratories, the largest of which are the LabCorps and Quest groups, have been short of capacity for weeks, which has created congestion. In early April, a hospital official in Virginia told AFP a wait of 5 to 7 days to receive the results for his patients.

These delays have now been eliminated, announced Wednesday the Federation of Laboratories, the American Clinical Laboratory Association. There are even "considerable unused capacity".

Rapid tests have also arrived on the market, using machines already widely present in clinics and medical offices: that of Abbott, ID NOW, delivers a result in a quarter of an hour.

One problem remains: in many places, for example in the capital Washington, the person cannot go for testing. You have to have symptoms and go through a doctor, when you know that a significant number of infected people have no symptoms.

- Cost -

The tests are supposed to be free, thanks to a law passed by Congress on March 18.

- Serology -

The above tests say whether or not a person is currently infected.

But the key to deconfinement will be to know who, in the past, has been contaminated and is potentially immune to re-infection.

To find out, another type of test exists, much simpler, from a drop of blood: serology tests, which look for antibodies. These antibodies are the memory of the immune system, which appear after an infection.

Authorities want to develop these tests in the hope that they will help determine who can return to work safely.

But they are not yet widely available. And their quality is variable, a problem compounded by the fact that the American drug agency, the FDA, after having delayed, authorized the industry to produce and distribute tests without approval.

Medical giant Abbott announced Wednesday that it will ship one million of the tests, with a total of four million by the end of April.

© 2020 AFP