I’ve had treatment for cancer twice and always pick up bugs. Mark rarely even gets a cold
weight. You’ll deteriorate faster. It doesn’t matter what put a patient into respiratory distress in the first place.
‘Huge amounts of evidence from anaesthesiology and general surgery tells us that if you’re obese, then your outcomes are worse on a ventilator.’
Could there also be a genetic explanation for the disparity? Scientists are trawling through DNA databases to try to work out why some people are more susceptible to the worst ravages of the disease than others.
But some already believe that basic differences between male and female immune systems may be a key factor.
Prof Goulder says: ‘It is becoming increasingly recognised that there are substantial differences in the immune system between males and females, and that these have a significant impact on outcome from a wide range of infectious diseases.
‘The immune response throughout life to vaccines and infections is typically more aggressive and more effective in females compared to males.’
Inside the nucleus of every cell, genetic material called DNA is packaged into thread-like structures called chromosomes.
These contain sequences of ‘code’ called genes, which determine how cells function and, as a result, everything from hair and eye colour to blood type.
The usual number of chromosomes in every cell in the body is 46 – or 23 pairs.
We inherit half from our mother and half from our father.
One pair are known as sex chromosomes and they determine whether a person is born male or female. The sex chromosomes in men and women differ in structure: women have two that are, when looked at under an extremely powerful microscope, shaped like an X. Men have one shaped like an X, and one like a Y.
A number of critical immune genes are located on the X chromosome, says Prof Goulder.
BECAUSE women have two copies of this chromosome and men only one, it means that women are better equipped to fight infection and viruses. When it comes to coronavirus specifically, there is a protein called TLR7 – again, on the X chromosome – which senses the Covid-19 infection.
This triggers a signal which results in the production of chemicals in the body called type one inferons. These ‘essentially have direct antiviral effects, but also amplify the innate immune response’, according to Prof Goulder.
‘It’s about recognising a threat and instigating a response. The more TLR7 receptors you have, the better that response.’
Men, who have only one X chromosome, therefore naturally have fewer TLR7 receptors to fight off coronavirus.
At first glance, this might seem to be a huge biological mistake. But Prof Goulder explains that this may have had an evolutionary advantage.
In theory, it is more important that women, who have to bear and raise children, are able to fight off infections, including viruses, and stay healthy.
For men, other evolutionary roles, such as attracting a mate and physical strength, were historically more advantageous.
Early man just didn’t need as strong an immune system as women, he says.
Other factors could include sex hormones such as testosterone, which suppresses the immune system.
Testosterone is often known as the male sex hormone as it is responsible for the development of sperm – although women also produce small amounts.
‘There’s a very nice study looking at the response to the flu vaccine in men and women,’ Prof Goulder says.
‘The women had higher antibody responses than the men, but the women with the lowest testosterone had the highest of all, and the worst response was seen in men with the most testosterone.’
Whether testosterone levels can also have an impact on coronavirus severity has yet to be investigated.
Now the big hope in clarifying the difference between the effects of coronavirus in men and women will come from the proposed rollout of antibody testing.
No test has yet proved reliable. Positive tests for coronavirus have appeared to show that men and women are roughly equally likely to be infected – 52 per cent compared with 48 per cent.
But an antibody test involving swathes of the population could reveal the truth, including whether women are more likely to be carriers, develop only mild symptoms, or develop a stronger antibody response than men.
Proof, perhaps, that man flu may not be a myth after all.