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The "man flu" is real, a new study suggests.

According to research conducted by a team at the Johns Hopkins Bloomberg School of Public Health, men tend to suffer more from the influenza A virus, which is commonly known as the flu, than women do due to the presence of estrogen.

For this study, the team headed by Sabra L. Klein, Ph.D., an associate professor in the Departments of Molecular Microbiology and Immunology and Biochemistry and Molecular Biology at the Bloomberg School, examined the nasal cells in men and women to see whether or not estrogen can effectively limit the flu from replicating in the infected cells of the body. In other studies, researchers have found that estrogen can limit the replication process for certain viruses, such as HIV and hepatitis.

They chose to look at nasal cells since the flu typically infects them first. The team exposed the cell samples to three types estrogen, which included normal levels of naturally occurring estrogen, different kinds of SERMs (selective estrogen receptor modulators), which are used for hormone replacement therapy and infertility treatments, and bisphenol A, which is chemical similar to estrogen that can be found in plastics. The team then exposed the nasal cells to the influenza A virus.

The researchers found that the female nasal cells that received estrogen had a reduced number of replications. In male nasal cells, estrogen did not lead to a lower amount of viral replications. The researchers explained that even though men naturally produce estrogen, their cells do not have as many receptors for the hormone as women's cells do.

The team noted that their findings can help prevent severe cases of influenza in older women.

"If women are taking estrogen-like hormones for other reasons, an added benefit might be less susceptibility to influenza during the flu season," Klein said reported by the press release. "Being on hormone replacement therapy could be one way to mitigate the severity of this disease, which is exciting, simple and cheap. While the decision to take hormone therapy should always depend on a patient's history and include discussion with their care providers, our study shows another potential benefit to this hormone."

The study's findings were published in the American Journal of Physiology.