As cases of the new coronavirus increase worldwide, research published last week by China's Center for Disease Control and Prevention suggests that men are more likely to die of the virus than women, despite men and women being infected at similar rates, Roni  Caryn Rabin reports for the New York Times.

Our analysis: The 'recurring themes' of disease outbreaks

Background

Reports of the new coronavirus first surfaced in early December 2019 in Wuhan, China. According to the World Health Organization (WHO), the main symptoms of the virus are fever and lesions in both lungs. Some patients also have reported difficulty breathing, WHO said.

As of Monday, officials reported 79,331 cases of the virus globally. Officials said as of Monday there have been about 2,600 reported deaths linked to the virus, and the vast majority of the deaths occurred in China. The majority of deaths have been among older adults, Caryn Rabin writes, while children have been "largely spared."

Men are more likely to die from new virus

New research from China has found that men, particularly middle-aged and older men, are having a harder time fighting off the virus than women. Chinese researchers found that while the infection rate among men and women is the same, the death rate among men is 2.8% compared with 1.7% for women.

According to Sabra Klein, a scientist at the Johns Hopkins Bloomberg School of Public Health, the pattern—men faring worse than women—is consistent with other viral respiratory infections. "Women fight them off better," she said.

Officials noticed this gender difference during the SARS and MERS outbreaks as well, according to Caryn Rabin. For instance, research found that in 2003 more women were infected by SARS in Hong Kong, but men died at rates 50% higher than women. And during the MERS outbreak, 32% of men died of the infection compared with 25.8% of women, Caryn Rabin reports.

Why are men more likely to die from the new coronavirus?

According to researchers, there are a few reasons men are more likely to die from the new coronavirus.

Women have a heightened immune response

Research on previous outbreaks shows that women have stronger immune responses to coronaviruses.

According to Janine Clayton, director of the Office of Research on Women's Health at NIH, "There's something about the immune system in females that is more exuberant," but researchers have yet to figure out what that is.

Some researchers think the higher level of estrogen, which contributes to immunity, and the fact that women have two X chromosomes, which carry immune-related genes, could factor into women's heightened immune response.

For instance, in one experiment, researchers exposed mice to SARS and found male mice were more susceptible to the infection and were slower to clear the virus. They also died at higher rates and experienced more lung damage, according to Stanley Perlman, senior author of the study and a professor of microbiology at the University of Iowa.

However, when the researchers blocked estrogen in the female mice and removed their ovaries, they were more likely to die from the virus. Blocking testosterone in the male mice on the other hand had no effect on the death rate.

Men and women have different health behaviors, conditions

Patients' existing health conditions and health behaviors can make them more susceptible to the virus, and increase their risk of death, Caryn Rabin reports.

When it comes to health behaviors, Caryn Rabin writes, China has the largest population of smokers in the world at 316 million people, but while more than 50% of Chinese men smoke, only about 2% of Chinese women partake in the behavior.

Chinese men also have higher rates of high blood pressure, Type 2 diabetes, and chronic obstructive pulmonary disease than women, all of which can increase the risk of complications and death from a coronavirus infection, Caryn Rabin reports.

According to a few unpublished Chinese studies, patients with delayed coronavirus diagnosis or who had pneumonia at the time of their diagnosis have an increased risk of death. And one study suggests men may be waiting to seek care, as they were more likely than women to present at hospitals with the disease at a more advanced stage.

Akiko Iwasaki, a professor of immunology at Yale University, added that men may have a "false sense of security" about coronavirus and similar diseases. When the outbreak first started, for instance, officials recommended that people wash their hands thoroughly and often to prevent infection, but multiple studies have found that men are less likely to wash their hands and use soap than women, according to Klein.

"We make these broad sweeping assumptions that men and women are the same behaviorally, in terms of comorbidities, biology and our immune system, and we just are not," he said (Rabin, New York Times, 2/20; WHO fact sheet, accessed 2/25).