The H7N9 bird flu virus is increasingly spreading among humans – men are infected more often than women. The interdisciplinary team has now got to the bottom of the gender gap.
Avian influenza viruses of the H7N9 subtype are characterized by high epidemic and pandemic potential. In March 2013, these bird flu viruses crossed species barriers and migrated from birds to humans for the first time. Men were affected more often than women. In the five epidemic waves that followed, the incidence of H7N9 was repeatedly higher in men than in women.
Low testosterone – poor prognosis
To unravel the mechanisms of these gender-specific differences, the German-Chinese team analyzed patients with confirmed H7N9 infection in the study and compared them with H7N9-negative close contacts and with patients with seasonal influenza infection. The researchers showed that H7N9 infection specifically attacks the hormonal axis in men, but not in women. In men, H7N9 infection results in low testosterone levels, which is associated with the development of serious or fatal disease.
Plan for further infections
Using mouse models, the authors confirm a causal relationship between H7N9 infection and testosterone deficiency in men. They also show that the H7N9 bird flu virus replicates in the testes of mice and causes local and systemic inflammation that likely affects testosterone production.
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To date, very little is known about the molecular mechanisms that lead to sex-specific disease progression in respiratory viral infections. This study could serve as a blueprint for studying gender differences in other respiratory infections such as SARS-CoV-2.
Peak season for bird flu
“Avian influenza viruses continue to pose a high epidemic and pandemic risk. The 2021/2022 season was the largest avian influenza outbreak on record anywhere in the world.” Understanding the molecular mechanisms that mediate the gender-specific course of the disease is therefore of fundamental importance for individual patient management,” explains prof. Gülşah Gabriel from the University of Veterinary Medicine in Hannover. Close surveillance and increased vigilance remain necessary to prevent the H7N9 virus from spreading to humans, experts said.
This text is based on a press release from the Leibniz Institute for Virology (LIV). The original publication can be found here.
Image source: Ravi Sharma, unsplash