Epidemiologists and virologists are scrambling to understand why the coronavirus that has infected hundreds of thousands of Americans appears to be so much more deadly for men than for women.

In most states across the country, data show that most of those who have tested positive for the virus are women. From the Deep South to New England states and the Midwest, most states have confirmed hundreds if not thousands more cases in women than in men, with a few notable exceptions.

But in states that report the genders of those who have died from the COVID-19 disease, every one has reported more deaths among men than among women, usually by a substantial margin — and scientists don't know why.

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In Michigan, one of the hardest hit states, 52 percent of the 21,500 people who have tested positive for the virus are women. But among the 959 who have died, 57 percent are men. In Indiana, 55 percent of confirmed cases are women, but men make up 60 percent of those who have succumbed to the disease.

Washington state, the first to confirm a coronavirus case in the United States, has seen more than 9,000 cases, a majority of which are women. But 57 percent of the 394 Washingtonians who have died are men. North Carolina has had 53 deaths, almost three-quarters of whom are men.

New York stands as the notable exception to the trend, one of the few states where more men have tested positive than women. Among the 150,000 New Yorkers who have tested positive, by far the most in the nation, men account for almost 55 percent of them. But like other states, men are more susceptible to the most dire outcomes: Almost 61 percent of those who have died from the coronavirus in New York are men.

The virus's greater mortality rate among men occurred in China, too, where the overwhelming number of the dead were men. A study by a joint mission of the World Health Organization and the Chinese Centers for Disease Control and Prevention found that the mortality rate among men who had confirmed COVID-19 cases was 4.7 percent, almost 2 full percentage points higher than women.

But there are major cultural differences between China, where men are far more likely than women to both smoke and be obese, and the United States, where smoking and obesity rates are much more similar between the two genders.

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"There is a gender issue here and it can't be accounted for just by obesity and smoking. Obesity is equal among both, smoking is about equal among both. None of us know," said Michael Osterholm, director of the Center for Infectious Disease Research and Prevention at the University of Minnesota.

Some speculate that men and women are at varying risks for other cultural reasons. In most societies around the world, women tend to be caregivers to the sick. When the Ebola virus broke out in three West African countries in 2014, and then again in the Democratic Republic of the Congo in 2018, women were far more likely to contract and die from the virus than men, largely because of their roles as caregivers to sick family and community members.

In the United States, about 90 percent of the nation's 4 million registered nurses are women, according to a 2013 survey by the National Center for Health Workforce Analysis. Figures from the Kaiser Family Foundation show that about 65 percent of the nation's 1 million doctors are men.

Dean Sidelinger, Oregon's state health officer and chief epidemiologist, said more testing among health care workers and those who work in assisted living facilities — the majority of whom are women — might be behind the larger share of women who are confirmed to have caught the virus. The public data may be missing many more cases among those who have not been tested, of either gender.

"If we prioritize testing of health care workers, folks who work in long term care facilities and congregate facilities, potentially the workforce may be driving that," Sidelinger said. "Anyone can get this disease. It doesn't matter where you're from, what gender you are or how old you are."

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A study published in The Lancet in March on behalf of the Gender and COVID-19 Working Group, a collection of researchers from across the globe, also suggested that because women are more likely to work in schools, they were more likely to be protected when governments ordered schools shuttered to combat the virus.

Disparities in health outcomes by gender are not unique to the coronavirus and COVID-19. Osterholm pointed to the common flu, which can have much more adverse effects on pregnant women than on other segments of the population.

"The immune system of a woman versus a man can surely make a difference," Osterholm said.