COVID-19 mortality twice as high for men in Italy as women What we know so far about COVID-19's gender divide.

Coronavirus mortality rate is twice as high among men in Italy as it is among women, marking a "concerning trend," Dr. Deborah Birx, the White House's coronavirus task force coordinator said during a Friday briefing.

"Mortality in males seems to be [twice higher than] every age group of females," Birx said, adding that no age group or gender is immune, and that mild symptoms are not equivalent to immunity.

According to Italy's public health research agency, 60% of coronavirus cases and 70% of deaths in the country so far have been in men.

In China, men were similarly more likely to die of coronavirus than women, although the disparity there was less stark. Sixty-four percent of deaths in China have been in men, according to recent figures from China's Center for Disease Control.

"While we do not know the causes of increased mortality in men, we do know that being male, much like being older, is a risk factor for more severe outcomes from COVID-19," Sabra Klein, a professor of molecular microbiology and immunology at Johns Hopkins Bloomberg School of Public Health said to ABC News.

It's notable, she added, that the trend holds true across two countries with distinct social and cultural norms.

"What should we do with this information?," Klein asked. "Men should be aware and maybe ensure they are being vigilant with hand-washing, social distancing, and taking any and all measures to avoid infection."

Why are men more likely to die from COVID-19?

At this point in time, most theories about why the virus might be hitting men harder than women are speculative, stressed Dr. Carlos del Rio, an infectious diseases expert and chair of the global health department at Emory University.

In many countries, and especially in China, men are more likely to smoke than women, which is a risk factor for developing more severe forms of COVID-19.

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There may also be biological differences at play.

"Females generally having greater or more robust immune responses than males," Klein noted, although she cautioned that whether this is true for COVID-19 still needs to be proven.

Del Rio seemed to agree. "Women do a lot better with other diseases than men do," he said.

Men are also more likely to suffer from some complicating conditions, like heart disease, stroke and hypertension, that put them at higher risk for severe outcomes from contracting coronavirus, Klein explained.

"Hypertension in particular has been suggested as an important risk factor and is more prevalent in men than women," she said. "This can be reflective of our biology as well as behaviors."

ABC News' Jordyn Phelps contributed to this report.