“We now have got an epicenter developing within Japan. Unless we stop it with a full force as a nation, I worry that we might go the same way as New York or Milan,” said Tatsuhiko Kodama, a professor at the University of Tokyo who is leading a research project on the virus.

In Australia and some other places such as Hong Kong and Israel, all of which had appeared to defeat the virus, infections are growing twice as quickly as in the United States, or even faster, suggesting there is no end in sight to the virus’s spread. A million new infections are being reported every four days worldwide, pushing the total well past 16 million cases…

Some of the countries where the case numbers are rising or raging are in the Southern Hemisphere, now experiencing midwinter, such as Brazil and Australia. But the new increases also are afflicting regions that had been bracing for a fall wave, predicted as people spend more time crowded together indoors and lower humidity facilitates the transmission of the virus, said Tim Spector, a professor of genetic epidemiology at King’s College in London. His team published a paper last week on how colder conditions affect the transmission of the novel coronavirus and the severity of covid-19, the illness the virus causes.

A worrying question now, Spector said, is how much worse the coronavirus spread will become when winter does arrive in the Northern Hemisphere.