Lifestyle Health and Wellbeing 15 Jan 2016 A flu that affects o ...

A flu that affects only men

Published Jan 15, 2016, 12:10 am IST
Updated Jan 15, 2016, 8:33 am IST
Female sex hormone, estrogen, protects women against the infection.
The amount a virus replicates determines its severity.
 The amount a virus replicates determines its severity.

It is a crippling, debilitating disorder that strikes indiscriminately, rendering men bedridden. Man flu may, to women the world over, be nothing more than an exaggeration, a feeble excuse for a day off work, a way to get out of doing the chores. And while it has long been said women have higher thresholds for pain and illness than their male counterparts, scientists have now added new evidence to the debate.

Their conclusion — man flu is a real phenomenon, and furthermore it is worse for men than women. Researchers discovered the shield that protects females from the more aggressive symptoms, is the sex hormone estrogen.


A team from Johns Hopkins University revealed estrogen has antiviral effects against the influenza A virus, commonly known as the flu. Lead study author Dr Sabra Klein said, “We see clinical potential in the finding that therapeutic estrogens that are used for treating infertility and menopause may also protect against the flu.”

Previous studies showed that estrogens also have antiviral properties against HIV, Ebola and hepatitis viruses. And so, the team of scientists sought out to determine if it has the same effect on the common flu.


A virus infects the body and causes illness by entering a cell and making copies of itself inside the host cell. And, when released from infected cells, the virus spreads throughout the body and between people. The amount a virus replicates determines its severity.

Thus, less replication of a virus means the infected person may experience a less virulent strain of disease — or is less likely to spread the disease to others. The researchers examined how estrogen affects the flu’s ability to replicate.

The team gathered nasal cells — which is the cell type the flu virus primarily infects — from both male and female donors. The cell cultures were exposed to the virus, estrogen, the environmental estrogen bisphenol A and selective estrogen receptor modules (SERM) — compounds that act like estrogen and are used in hormone therapy.


The scientists determined that estrogen, SERM compound raloxifene and bisphenol A reduced flu virus replication in nasal cells from women. However, they were not found to reduce the virus in men. Furthermore, the team found that the estrogens initiated their antiviral effects through estrogen receptor beta.

Dr Klein said, “What makes our study unique is two-fold. First, we conducted our study using primary cells directly isolated from patients, allowing us to directly identify the sex-specific effect of estrogens. Second, this is the first study to identify the estrogen receptor responsible for the antiviral effects of estrogens, bringing us closer to understanding the mechanisms mediating this conserved antiviral effect of estrogens.”


The study’s findings support earlier evidence showing the protective effects of estrogen against the flu in animals.