Coronavirus tests: which approach is most effective?

The Asian countries hardest hit by the coronavirus have each adopted a different approach to testing, which raises the question of which strategy has been most effective.

Official data suggests the rate of new infections in China, where the epidemic started, and South Korea is slowing down.

But while some experts have announced the results as warning signs of success, others warn that there could be problems with subtests and accuracy, which raises delicate questions for global decision makers. In the United States, where Donald Trump contradicted his own officials during the crisis, authorities have been accused of not having tested aggressively enough.

How did Asian countries facing the biggest epidemics and Italy, the European country with the biggest crisis, use the tests?

China focuses on most serious cases

The coronavirus has infected more than 80,000 people and killed more than 3,000 in mainland China, but the number of new infections reported every day is decreasing, according to the government. Authorities said on Tuesday that the number of new cases fell to their lowest level since January.

Beijing said it shows that locking millions of people has worked.

Epidemiologists warn, however, that the lack of testing capacity has led to a vast underestimation of the number of coronavirus cases. China's propensity to exclude less severe cases from its screening regime means that the ratio of deaths to confirmed cases is 3.91%, which is probably a higher figure than if more people were tested.

The problem is particularly acute in Wuhan City, where the virus originated.

Wang Jing, a nurse at Wuhan Union Hospital West, said his hospital "must be stingy" with test kits. At the start of the epidemic, "if the patient was not showing severe symptoms, then a test kit should not be wasted," she said.

The supply of test kits has improved and Ms. Wang is now trying to check the backlog of "suspected cases" at her hospital. But they are always asked to exercise discretion in deciding who to test.

The problem of testing capacity in China is exacerbated by the low sensitivity of testing: Chinese experts say that only 30-50% of positive cases are detected with the kits available in the country.

To avoid sampling errors that cloud understanding of the spread of the virus, Benjamin Cowling, chief of epidemiology at the University of Hong Kong, suggested periodically testing a random sample to monitor the spread of the disease.

South Korea aggressively tested

On Wednesday, South Korea reported 242 new cases of coronavirus, bringing the total number to 7,755. This increase came after the identification of a new group of infections at a health center Called Seoul and marked a four-day reversal of new declining infections.

Seoul launched a mass public testing program in response to an epidemic that has spread to Daegu, the country's fourth city. Authorities have sought to test anyone who may have been exposed to the virus, including many asymptomatic patients as well as those with symptoms. Over 210,000 tests were performed and up to 10,000 new tests were performed each day. The mortality rate remained below 1%.

"To control the epidemic, the best information you have is these tests, which tell you which is positive and which is not," said Kee Park, professor at Harvard Medical School.

Hong Ki-ho, a doctor at the Seoul Medical Center, estimates that the country's accuracy in coronavirus testing is "99% – the highest in the world". He highlighted the rapid commercial development and deployment of new test kits through an accelerated regulatory process.

"We have authorized test kits based on WHO protocols and have never followed China's test methods," said Dr. Hong.

However, Choi Jae-wook, a professor of preventive medicine at the University of Korea, remained "worried".

"Many of the kits used at the start of the epidemic were the same as in China, where the accuracy was questioned. . . We were hesitant to voice our concern because it could cause even more public concern, "said Mr. Choi.

Japan accused of failing to test enough

For weeks after the start of the epidemic, Japan only tested people with ties to Wuhan, the heart of the epidemic in China, giving authorities little chance of detecting early household infections.

Japan has tested fewer than 10,000 people and 513 diagnoses have been confirmed, according to the Ministry of Health, Labor and Welfare. Some patients first consulted a doctor with symptoms a week or 10 days before the test.

Critics say the government is trying to minimize the number of cases to save the Tokyo Olympics this summer.

But Yasuyuki Sahara, senior assistant minister at the MHLW, said the reality was more prosaic: capacity limited to polymerase chain reaction tests used to confirm the presence of the virus.

"Initially, we could only do PCR tests at the National Institute of Infectious Diseases, but now it extends to universities, quarantine stations and private companies", a- he declared.

Tokyo prioritized the accuracy of volume testing, with centralized control over who was tested. This explains why South Korea was able to increase the tests when Japan could not.

“The PCR tests we do are not necessarily the same as those in South Korea. PCR tests vary in speed and sensitivity, "said Sahara. "In Japan, we place great importance on providing an extremely accurate PCR test."

Under pressure from Prime Minister Shinzo Abe, authorities have relaxed the requirement to contact Wuhan and plan to cover coronavirus testing on national health insurance.

However, the number of tests carried out remains below the capacity claimed by Japan of 4,000 per day.

Italy has adopted a strategy similar to South Korea

Italy has quarantined the whole country after an epidemic that started in the north of the country has turned into a national crisis. The death toll has jumped to over 600 and confirmed cases exceed 10,000.

Italy has tested anyone who may have been exposed to the virus, as well as those with symptoms.

“Especially during the initial phase of contagion, the strategy of over-testing was certainly fair and sensible. At a time when the problem was minor, the authorities decided to make an assessment of the situation, "said Fabrizio Pregliasco, virologist at the University of Milan.

"This has been helpful in tracking suspicious cases and trying to trace the way the virus has spread as completely as possible."

Additional reporting by Song Jung-a and Kang Buseong in Seoul and Robin Yu in Hong Kong