New research has - once again - appeared to prove the existence of the much-contested 'man flu'. The study, published by researchers at Johns Hopkins University, suggests that the female sex hormone oestrogen could help women combat the virus, leaving lesser-protected men out in the cold. Oestrogen, which is found at considerably higher levels in women than in men, was found to reduce the replication of the 'influenza A' virus in nasal cells, thereby initiating antiviral effects against the disease. The American study analysed nasal cells from male and female donors "A virus infects and causes sickness by entering a cell and making copies of itself inside the host cell," explains lead investigator Dr Sabra Klein. "When released from infected cells, the virus can spread through the body and between people. How much a virus has replicated determines its severity. "Less replication of the virus means the infected person may experience less disease," Klein continues, "or is less likely to spread the disease to someone else." Therefore, as the female body can contain up to 24 times the amount of oestrogen as the male body, women appear to be considerably better equipped to defend themselves against the replication of the 'influenza A' virus than men. The male body contains considerably less oestrogen than the female To examine how oestrogen affected the flu virus’s ability to replicate, the research team gathered nasal cells - the cell type that the flu virus primarily infects - from male and female donors. They then exposed these cells to the 'influenza A' virus and discovered that while the female samples initiated their antiviral effects, the male samples did not. "Other studies have shown that oestrogen has antiviral properties against HIV, Ebola and hepatitis viruses," says Klein. "But what makes our investigation unique is that we conducted our study using primary cells directly isolated from patients, allowing us to directly identify the sex-specific effect of oestrogens." However, despite the proof that oestrogen defends against the onset of flu, Klein and her team of researchers believe that hormonal cycles may mask its beneficial effects in everyday life. "Because oestrogen levels cycle in premenopausal women," acknowledges Klein, "it may be difficult to see this protective effect in the general population. But, premenopausal women on certain kinds of birth control or post-menopausal women on hormone replacement may be better protected during seasonal influenza epidemics.” Previous studies have found that high levels of testosterone, the primary male sex hormone, can weaken an individual's immune system - suggesting that men pulled the short straw when it comes to both hormones in relation to winter germs. A 2013 study by researchers at Stanford University showed that high levels of testosterone can weaken a man’s immune response to the flu shot compared to women who are vaccinated against the virus. Source
