The novel coronavirus, which causes COVID-19, is an “equal-opportunity virus” says Dr. Cara Tannenbaum, scientific director of the Institute of Gender and Health for the Canadian Institutes of Health Research.
It seems to infect men and women equally, with about the same number of cases appearing in males and females, according to international data.
“If the virus is in anyone, it’s happy to be transmitted to anyone,” Tannenbaum said.
But it seems that the virus might have different effects on male and female bodies.
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According to new international data analyzed this week by researchers in the BMJ, many more men than women have died as a result of COVID-19, though not all countries broke down their deaths by sex.
In Italy, 71 per cent of reported deaths have been men.
In China, it was 64 per cent, even though men accounted for around half of the total cases.
And so far, researchers aren’t really sure why.
It could have something to do with men’s health and behaviour, suggested Dr. Gerald Evans, chair of the division of infectious diseases at Queen’s University.
“It’s not a variable that’s totally dependent on their sex, but rather on the fact that there are certain habits and diseases that are more commonly seen in men than women,” he said.
Men tend to have higher rates of cardiovascular and respiratory disease, and tend to smoke and drink at higher rates than women, he said, which might make them more susceptible to developing a severe form of COVID-19 — a possible explanation also suggested by the authors of the BMJ piece.
This gendered behaviour could contribute to the higher death rates among men, Tannenbaum said.
“Men are more likely to smoke. We saw that especially in some of the Asian countries, like China,” she said.
“And once your lungs have been affected by the smoke, they’re unable to deal with fighting off the virus as well.”
There might also be factors related to biological sex that explain how the virus affects males and females differently, she said, though she’s careful to note that these are all just speculations at this point.
The virus connects to and enters your cells via a “receptor,” she said, which she describes like a code punched in on a keypad, granting access. In this case, the receptor is called ACE-2, and it’s controlled by a gene on the X chromosome, she said.
Females have two X chromosomes, and males have one X and one Y chromosome. “And so the fact that men don’t have two X chromosomes, right away you wonder if that puts them at an advantage or disadvantage for getting sick,” Tannenbaum said.
The ACE-2 receptor “seems to be over-expressed in men, meaning there’s more doors for the virus to get into the cell,” she said.
So while it’s not at all been proven that this sex difference in the ACE-2 receptor has anything to do with how severe the disease gets, Tannenbaum said, it’s “kind of interesting.”
So, too, are some genetic differences in specific proteins and sensors involved in the immune response to the virus, though this would also require confirmation, she said.
The female immune system also responds differently to attack and produces antibodies differently than the male, she said.
“We see this with the flu vaccine. When you give the same dose of flu vaccine to men and women, women will mount twice the antibody response to the flu vaccine than men.”
Differing amounts of hormones, like estrogen and testosterone, might also contribute to different kinds of responses, she said.
The authors of the article in the BMJ suggest an even simpler explanation: that the data itself might be skewed, given differences in different countries’ health systems and reporting techniques.
“At this early stage of each epidemic, the case fatality ratio does not measure true mortality,” they wrote.
“Findings from previous coronavirus infection outbreaks, however, lead us to suspect this is not simply a reporting artefact.”
While there are many different potential explanations, they’re all hypotheses at this point.
“I would not be telling men, ‘Oh, you’ve got more to worry about than women,’” Evans said.
“Until we get this all sorted out and figured out, in my view, it creates fear and anxiety that’s not warranted until we have much better analysis of the data.”
Having that sex and gender analysis is important for research, Tannenbaum said. “Whenever we see such a big difference, we think maybe it can explain how the virus works.”
“So do women have a protective factor that we can then use to help men or do men have a susceptibility that would help us better understand how the virus attacks and how we could develop a treatment?”
Better understanding how men and women respond to potential treatments and vaccines can also help tailor them for each sex, she said — for example, by giving women a smaller dose if it’s proven that they will have a sufficient immune response with less vaccine.
Tannenbaum wants to see more researchers digging into these sex and gender differences when it comes to COVID-19.
“I’m very intrigued to find an explanation for this.”
Questions about COVID-19? Here are some things you need to know:
Health officials caution against all international travel. Returning travellers are legally obligated to self-isolate for 14 days, beginning March 26, in case they develop symptoms and to prevent spreading the virus to others. Some provinces and territories have also implemented additional recommendations or enforcement measures to ensure those returning to the area self-isolate.
Symptoms can include fever, cough and difficulty breathing — very similar to a cold or flu. Some people can develop a more severe illness. People most at risk of this include older adults and people with severe chronic medical conditions like heart, lung or kidney disease. If you develop symptoms, contact public health authorities.
To prevent the virus from spreading, experts recommend frequent handwashing and coughing into your sleeve. They also recommend minimizing contact with others, staying home as much as possible and maintaining a distance of two metres from other people if you go out.
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