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The new coronavirus raced through China much faster than previously thought, a U.S. research team said, suggesting that extremely widespread vaccination or immunity will be necessary to end the pandemic.

Each person infected early in the epidemic in Wuhan probably passed the virus to an average of 5.7 other people, according to a mathematical analysis from Los Alamos National Laboratory. That’s more than twice what the World Health Organization and other public health authorities reported in February.

The team’s results are specific to the Chinese outbreak. If they hold true elsewhere in the world, the pandemic may be more difficult to control than some authorities had modeled.

At the rate of spread calculated in the study, some 82% of the population would need to be immune, either via a vaccine or because they’d already had the disease, in order to stop the virus from spreading, the Los Alamos team said. Without such protection, high levels of social distancing will be needed if more than one out of five infectious people is undiagnosed, the authors said.

Governments around the world are trying to figure out when and how to emerge from weeks of lockdown, even as some parts of China renew restrictions after a fresh flare-up. Nearly 1.5 million people have tested positive globally, including a number of recent cases in China with none of the typical symptoms of COVID-19.

“To think we’re close to an endpoint would be dangerous,” Hans Kluge, the WHO’s regional director for Europe, said at a briefing on Wednesday. The WHO has said a renewed push to test patients, isolate them and trace their close contacts will be needed as countries gradually loosen restrictions on public life.

The Los Alamos report, published in Emerging Infectious Diseases, used mobile phone travel data and case reports of coronavirus outside the early epicenter in China’s Hubei province to calculate its spread. The decline in newly confirmed cases in China and South Korea in March shows it can be contained, the report said.

Pollution linked

Americans in communities with higher smog levels are at greater risk of dying from COVID-19, according to a new study that suggests the health damage from the novel coronavirus has been worsened by long-term exposure to air pollution.

Scientists at Harvard T.H. Chan School of Public Health analyzed data on more than 3,000 U.S. counties to link small increases in long-term exposure to fine-particle pollution to substantially higher death rates from the coronavirus.

Researchers calculated long-term average levels of fine-particle pollution — lung-damaging soot also known as PM2.5 — from 2000 to 2016 and compared it to the more than 7,000 COVID-19 deaths that had occurred through April 4. They found that an increase of only one microgram per cubic meter of PM2.5 was associated with a 15% rise in the coronavirus death rate.

Francesca Dominici, a professor of biostatistics at Harvard and coauthor of the study, said her team fast-tracked its research in response to the surge in coronavirus deaths out of a “moral obligation” to help inform the response to the health crisis. The scientists released their manuscript before publication, while it undergoes peer review, and made public their data and code, hoping that it can be used worldwide to help focus research and prevent deaths.

Dominici said it was, to her knowledge, the first nationwide study to quantify the relationship between coronavirus death rates and exposure to one of the most widespread types of air pollution. She said she wanted to get the information out as soon as possible because it suggests health officials should pay closer attention to limiting the damage in the worst-polluted communities.

Los Angeles Times contributed

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