Medical experts in Japan say people who are recovering from the coronavirus at home should frequently check their blood oxygen levels because their conditions could worsen without noticeable symptoms.
Some of those who become moderately ill after developing pneumonia show no signs of distress, despite a low oxygen intake. The condition is called happy hypoxia.
A surge in coronavirus cases is overwhelming Japan's hospitals, especially in the Tokyo area and the southern prefecture of Okinawa. Many infected people have little choice but to stay at home.
Experts advise them to use a pulse oximeter to frequently check their oxygen levels, and to seek medical help for any abnormalities.
Toho University Professor Tateda Kazuhiro, who is a member of the government's coronavirus advisory panel, says they could suddenly lose consciousness and become severely ill.
He says they should not hesitate to call their local public health center or a hospital if they start feeling hazy, or experience discolored lips or fingernails.
Tateda also says it's important to have more than one place to contact in an emergency.
