This is part 51 of our coronavirus FAQ. Click here to read other installments: #Coronavirus the facts. Find the latest information and answers from experts on everything COVID-19.
Japan's fatality rate in May
The National Institute of Infectious Diseases has come up with an adjusted mortality rate of 7.2 percent for a one-month period ending in late May. The data is for people infected in Japan.
It shows that the rate increased with age. In people younger than 70, it was 1.3 percent. For people 70 or older, it was 25.5 percent.
Expanded testing lowers rate
An analysis of data in Japan for the month of August shows a much lower fatality rate. Overall, it was 0.9 percent. For people younger than 70, it was 0.2 percent. For people 70 or older, it was 8.1 percent.
So, why such a marked fall? Researchers at the institute believe doctors prioritized diagnosing and treating patients in serious condition during the initial outbreak, which pushed up the fatality rate. They say the higher number of people with light or no symptoms following an expansion of PCR and other tests is believed to have pushed the rate down.
As of now, the experts see no sign that the virus has become any less fatal. They believe the latest figures provide a more accurate picture of the actual fatality rate.
The experts also cite improved treatment methods as another possible reason for the declining fatality rate.
During the initial stage of the outbreak, doctors focused on how to treat pneumonia and Acute Respiratory Distress Syndrome. Later, they found there are two other factors that cause people to become critically ill: blood clots, and a cytokine storm, an overreaction of the immune system, which can then attack the person's own body.
Tiny clots tend to form in the blood vessels of people infected with the coronavirus. Experts have found that these can travel to various organs and block blood flow, causing a heart attack, stroke or other problems.
The experts say many people who tested positive for the coronavirus and then suffered multiple organ failure likely suffered a cytokine storm.
This information is accurate as of Sept. 15.