How does testing for the coronavirus work? | Science| In-depth reporting on science and technology | DW | 04.03.2020
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Science

How does testing for the coronavirus work?

Who should be tested for the coronavirus — and how? Here's what you need to know about being tested for COVID-19, and what testing may look like in the future.

There are no drugs or vaccines for the new coronavirus. It will take at least 18 to 24 months before an appropriate vaccine can be developed, tested for side effects in all test phases, approved by the health authorities, and then produced in large quantities and delivered globally. And then people will have to be vaccinated.

As such, reliable tests in the coming months are the most sensible measure to at least slow the further spread of the virus. Tests can be used to identify infected people and possible "hot spots." This is the only way to quarantine those infected — whether in a medical facility or, in the case of a mild course, isolated at home.

However, even in well-developed countries, medical facilities and laboratories quickly reach the limits of their capacity during an acute wave of infection. For this reason, rapid tests must be limited to genuinely suspicious cases; a general test of all is neither possible nor useful.

Who is tested?

According to current estimates, simply being in a risk area is not enough to justify a test. And not everyone with a cold or cough is infected with COVID-19 immediately.

However, anyone who shows signs of virus-induced pneumonia of "unclear cause," anyone who shows conspicuous symptoms such as coughing, fever and shortness of breath and who has also either had contact with an infected person or has stayed in a particularly affected risk region is a justified suspect case.

Ultimately, it is at the discretion of the doctor whether a coronavirus test is carried out or not. According to the Robert Koch Institute, random samples of patients with flu symptoms are also tested for the novel coronavirus.

In Germany, the costs (approximately €200 or $220) are covered by health insurance companies, but only if the patient is actually classified as a suspected case by the doctor.

Südkorea Gwangju | Menschen werden in Autos auf Covid-19 getestet

South Korea has set up "corona drive-ins" for tests in several cities

How is the test carried out?

In most cases, the test involves taking a throat swab or a throat-nose swab from the patient. The Robert Koch Institute also recommends that, in the case of a well-founded suspicion, samples should not only be taken from the upper airways but also from the lower airways, for example from coughing up secretions from the bronchi or lungs.

What happens with the samples?

The samples are tested for coronavirus in diagnostic laboratories. The procedure is based on a so-called polymerase chain reaction (PCR). Such tests take about five hours and have become standard procedures in laboratories. They are also used to clarify hereditary diseases or to determine paternity.

In PCR, a specifically selected piece of DNA is copied and multiplied in a thermocycler in order to search for specific DNA pieces, such as coronavirus. The method then shows whether and how many pathogens are present in the body. In viral infections, this is called the "viral load."

How to inform those affected?

The actual test takes about five hours, plus the transport time to the test laboratory. The results are usually available after one or two days, after which the doctor informs the patients.

If the test result is positive, the patient and the respective health authority are informed immediately. If necessary, this is followed by inpatient admission with specially designed isolation rooms and protective measures.

In the case of mild disease progression, patients can also remain at home in isolation as long as it is ensured that they cannot infect third parties.

Symbolbild - DNA-Labor

Even a negative test does not completely exclude a possible infection with the coronavirus

Are the tests clear?

The tests are, but even a negative test does not completely rule out a possible coronavirus infection.

Why? If the samples were taken incorrectly, if the samples were transported incorrectly or if the samples were taken at the wrong time, a negative result can be obtained incorrectly. This is another reason why presumably infected patients are tested several times.

Are there also simpler and faster test options?

As described, diagnosis using polymerase chain reaction requires very special laboratory equipment and highly qualified technicians, which are not available in many parts of the world. Even in well-developed China, laboratory capacities were quickly exhausted due to the large number of cases. In Europe and the US, too, there are sometimes delivery problems with tests, individual test components or medical equipment. 

After the tragic Ebola and Zika crises, researchers have wanted to develop a portable version of these molecular diagnostic devices in order to be able to test people in less well-equipped clinics or at some point decentralized in their home country or at home.

Research is being carried out worldwide and the first promising approaches for a simplified rapid test, similar to a blood sugar test, are already available. For example, the test presented by China's National Health Commission will be able to detect immunoglobulins, the antibodies that the human body first produces in a new infection, by testing a drop of blood in just 15 minutes.

Duke-NUS Medical School in Singapore has developed a similar antibody test, which has already been successfully tested by the Singapore Ministry of Health.

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