Questioning the accuracy of the high number, the Kanagawa prefectural government on Feb. 9 temporarily stopped releasing the rate of people who have taken a test and tested positive for COVID-19.

There has been a delay in reporting the number of tests taken, leading to the positivity rate exceeding 80 percent, an abnormal situation, officials said.

The prefectural government posted a notice on its website as of Feb. 8, which says, “Since it has been difficult to know the number of tests taken, we will temporarily stop releasing the number of tests taken and the positivity rate.”

As of the evening of Feb. 9, a chart of the positivity rate had been pulled from the prefectural website.

The weekly average of the positivity rate in the prefecture as of Feb. 7 was 84.93 percent.

That means of 100 people taking a test, about 85 people tested positive for the novel coronavirus.

That compares to the 2 percent positivity rate as of Jan. 7. 

In the prefecture, an increasing number of infection clusters at nursing homes and at-home infections have been reported, officials said.

It is likely that the positivity rate has gone up because people who are believed to be infected with the virus have taken a test, officials said.

But at the height of the fifth wave of the pandemic last summer, the positivity rate did not exceed 30 percent in the prefecture.

“Reporting the number of tests taken has been bogged down because health care organizations are overwhelmed,” said a prefectural official.

The prefectural government has received reports on the number of both an administrative test that is available for people who are deemed a close contact and are symptomatic and a voluntary test that people with no symptoms take to obtain a certificate of a negative result.

The positivity rate is calculated by using the number of tests for a denominator and the number of new infection cases each day for a numerator.

But the task of testing has been strained at health care organizations and other entities. Reporting the number of tests taken has slowed, and the denominator has been smaller than the actual number, officials said.

There is another factor that increases the positivity rate, even though it does not have much impact at the moment, officials said.

In Kanagawa Prefecture, people who have tested positive on a commercially available test kit are deemed as patients “who are voluntarily recuperating at home.”

Such people are asked to monitor their own health conditions.

The number of such patients has been treated as a COVID-19 patient and included in the numerator to calculate the positive rate.

But officials do not know the number of tests taken by such people. Therefore, the denominator has not increased.

Furthermore, people who have no symptoms but are concerned about an infection and take a free test available at pharmacies and others are not always counted and only the numerator has increased because of that.

The prefectural official said, “What we can read from the positivity rate changes as the subject and system of testing change. We need to sort it out from now on.”

In Tokyo, the positivity rate as of Feb. 8 was about 40 percent, higher than the peak of the fifth wave of the pandemic. 

A metropolitan government official said only the number of administrative tests taken and the number of infected people who have taken these tests have been used to calculate the positivity rate in the capital.

The reason why the positivity rate has risen is likely that people who are symptomatic and are highly likely infected with the virus have visited health care organizations.

At the same time, the metropolitan government has publicly released the weekly number of free tests taken, which is for people with no symptoms, and the number of suspected positive cases as the result of these tests, as well as the number of tests taken weekly at nursing homes and restaurants, on its website.

Calculating the rate of suspected positivity in the week until Feb. 6 by using these figures, it was 0.5 percent at nursing homes and others, 4 percent at bars and restaurants and 7.4 percent for tests taken by people with no symptoms.

Each of these figures has risen compared from the previous week.

But it is not as high as the positivity rate shown in the administrative testing, officials said.

The official said, “We have started a project to mail a test kit to people who are deemed to be a close contact (of an infected person). People who need to take a test have been able to take a test.”