Mystery: Why are Europe, U.S. harder hit than Asia?
TOKYO — It is one of the many mysteries of the coronavirus pandemic: Why has the death toll from COVID-19 apparently been lower in Asia than in Western Europe and North America?
Even allowing for different testing policies and counting methods, and questions over full disclosure of cases, stark differences in mortality across the world have caught the attention of researchers trying to crack the coronavirus code.
What are the numbers? China, where the virus emerged late last year in Wuhan, has recorded fewer than 5,000 deaths, which translates to three deaths per million inhabitants. Japan has around seven per million, Pakistan six, South Korea and Indonesia five, India three and Thailand fewer than one per million. Vietnam, Cambodia and Mongolia say they have recorded zero COVID-19-related deaths.
Compare that with about 100 deaths per million in Germany, about 180 in Canada, nearly 300 in the United States and more than 500 in Britain, Italy and Spain.
Scientists at Japan’s Chiba University plotted the trajectory of the virus across the world and said they noticed stark regional disparities.
“That means we need to take into consideration regional differences first, before analyzing what policies and other factors are affecting the spread of infection in any given country,” said Akihiro Hisaka of the university’s Graduate School of Pharmaceutical Sciences.
Part of the reason for the high number of deaths in the United States and Western Europe may lie in an initial reluctance to react to an epidemic that seemed distant and unthreatening. In Asia, meanwhile, previous experience with the SARS and MERS epidemics enabled much faster responses to the new threat.
Taiwan has been widely praised for its speedy response to the epidemic, including early screening of air passengers from Wuhan. South Korea built a massive program of testing, tracing and isolating patients.
Demographics also play a role in regional disparities. Africa’s generally younger population may have been more resistant than northern Italy’s older communities, for example.
In Japan, which has the world’s oldest population, different reasons are being explored. There is a widespread belief in Japan that good hygiene and habits, like wearing masks and avoiding handshakes, helped slow the spread of the virus, while universal health care and the country’s emphasis on protecting the elderly may have lowered the death toll.
Nobel laureate Tasuku Honjo, a Japanese physician-scientist and immunologist, said people with Asian and European ancestry have enormous differences in the human leukocyte antigen (HLA) haplotype, genes that control the immune system’s response to a virus.
That might help explain lower Asian death rates, he said, but is unlikely to be the only reason.
Tatsuhiko Kodama of the University of Tokyo said preliminary studies show that Japanese people’s immune systems tend to react to the novel coronavirus as though they had previous exposure, and notes that there are centuries of history of coronaviruses emerging from East Asia.
“The enigma of lower death rates in East Asia can be explained by the presence of immunity,” he said.
All the epidemiological research on the virus suffers from incomplete data, and any conclusions drawn from the initial numbers may melt away as new data emerges. It is still early in the pandemic, experts say, and the hard-science questions take time.
In any case, it doesn’t change the need for every country to remain on high alert.
“All of the strains that are circulating on the planet,” said UMass professor Luban, “seem to be capable of killing people.”