Scientists believe that males could be more vulnerable to the coronavirus because they may have a weaker immune response to the disease, according to a column by The Financial Times.

The virus has killed roughly 1,300 people and infected over 48,000 worldwide as of Thursday. Another case was discovered in San Diego Calif. on Wednesday, bringing the total U.S. infected to 14.

Roughly two-thirds of 99 infected patients admitted to a Wuhan hospital last month were men, science writer Anjana Ahuja wrote, citing a Lancet medical study published on Jan. 30.

“It is an eye-catching discrepancy,” Ahuja wrote. “A picture is emerging of 2019-nCoV [now COVID-19] as a novel pathogen that disproportionately affects older men, particularly those with existing illnesses such as heart disease and diabetes.”

She said possible reasons for the differences between men and women could be smoking, a variation of hospital treatment and hormonal differences which could impact males’ immune system response.

Females are prone to autoimmune diseases, which causes parts of their immune system to become stronger to compensate, resulting in a possible stronger response to the coronavirus, according to FT. Women routinely outlive men by six to eight years and are more likely to reach their first birthday, according to the World Health Organization [WHO].

Stanley Perlman, an immunologist at the University of Iowa and his colleagues suggested that hormones, including Estrogen, could be a possible defense against the virus.

Perlman studied how SARS — a disease often compared with coronavirus — impacts male and female mice. He concluded that male mice were affected in greater number, while adding that his study was consistent across coronaviruses as well, according to FT.

Two studies on SARS and MERS [Middle East respiratory syndrome] patients found that males had a higher death rate for both diseases.

One study showed that out of 1,800 Sars patients — men had a 9 percent higher date rate. A 2019 study of 229 Mers patients showed found that males had a six percent higher death rate over females, FT reported.

“Some scientists are now convinced that these sex differences in clinical data reflect a genuine male vulnerability to coronavirus, rather than a bias in exposure,” Ahuja said. “The observations add to growing evidence that immunologically speaking, men are the weaker sex.”