Amid the steady stream of stories on the lives lost to coronavirus are cases that stand out as remarkable. In the past month, at least two pairs of twins have died in Britain and two pairs of brothers, all within hours or days of each other. But do the deaths point to genetic factors that make some more likely than others to succumb to the disease?

Most scientists believe that genes play a role in how people respond to infections. A persons genetic makeup may influence the receptors that the coronavirus uses to invade human cells. How resilient the person is to the infection, their general health, and how the immune system reacts will also have some genetic component.

A team led by Prof Tim Spector, head of twin research and genetic epidemiology at Kings College London, has reported that Covid-19 symptoms appear to be 50% genetic. But Spector said more work is needed to understand which genes are involved and what difference they make to the course of the disease. We dont know if there are genes linked to the receptors or genes linked to how the infection presents, he said.

Identical twins Katy and Emma Davis, aged 37, died at Southampton general hospital last month. The sisters, who lived together, had underlying health problems and had been ill for some time before they contracted the virus. Another pair of twins, Eleanor Andrews and her sister Eileen, aged 66, died earlier this month. They too lived together and had underlying health conditions.

Two brothers from Newport, Ghulam Abbas, 59, and Raza Abbas, 54, died within hours of each other at Royal Gwent hospital. Another pair of brothers from Luton, Olume Ivowi, 46, and Isi Ivowi, 38, died within days of each other.

These deaths alert people to the fact that this could be genetic, but when people live together they share an environment as well, Spector said. The upshot is that twins who live together are more likely to have similar lifestyles and behaviours, from diet and exercise habits to how quickly they seek medical care. Twins are not generally less healthy than the wider population.

Twin deaths made headlines long before the coronavirus struck. When Julian and Adrian Riester died on the same day in Florida in 2011, a cousin of the twin Franciscan monks said it was confirmation that God favoured them. But Spector sees the hand of cold statistics at work. When you look formally at this, you see that twins rarely die at the same time, he said. There are billions of people on the planet. One in 70 is a twin and one in 200 is an identical twin.

Marcus Munafo, professor of biological psychiatry at Bristol University, said reports of twin deaths must be interpreted with caution. Twin deaths are unusual, which makes them newsworthy, but coverage can distort our perceptions. Salience bias refers to the fact that we tend to focus on information that stands out more, even if its not particularly relevant. So we need to be careful not to read too much into events that might stand out for reasons that are not actually related to the issue were interested in, he said.

When twins or siblings tragically die with Covid-19 that captures our attention, but that doesnt mean theres any particular reason to think twins or siblings are at greater risk.

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Genetics in focus after coronavirus deaths of siblings and twins - The Guardian