Dödligt virus från Kina orsakar panik (SARS-CoV-2, COVID-19)

Why do some COVID-19 patients infect many others, whereas most don’t spread the virus at all?
By Kai Kupferschmidt May. 19, 2020 , 5:25 PM
...
Most of the discussion around the spread of SARS-CoV-2 has concentrated on the average number of new infections caused by each patient. Without social distancing, this reproduction number (R) is about three. But in real life, some people infect many others and others don’t spread the disease at all. In fact, the latter is the norm, Lloyd-Smith says: “The consistent pattern is that the most common number is zero. Most people do not transmit.”

That’s why in addition to R, scientists use a value called the dispersion factor (k), which describes how much a disease clusters. The lower k is, the more transmission comes from a small number of people. ...

Estimates of k for SARS-CoV-2 vary. In January, Julien Riou and Christian Althaus at the University of Bern simulated the epidemic in China for different combinations of R and k and compared the outcomes with what had actually taken place. They concluded that k for COVID-19 is somewhat higher than for SARS and MERS. ... But in a recent preprint, Adam Kucharski of LSHTM estimated that k for COVID-19 is as low as 0.1. “Probably about 10% of cases lead to 80% of the spread,” Kucharski says.

Vitamin D supplements may offer no Covid benefits, data suggests
Two studies fail to find evidence to support claims supplements protect against coronavirus

The idea that vitamin D supplements can reduce susceptibility to, and the severity of, Covid-19 is seductive – it offers a simple, elegant solution to a very complex and lethal problem. But analyses encompassing large European datasets suggest the enthusiasm for the sunshine vitamin may be misplaced.

Two still to be peer-reviewed papers looked at the link between vitamin D levels and Covid-19 and both reached the same conclusion: evidence for a direct link between vitamin D deficiency and Covid outcomes is lacking.

Vitamin D supplements may offer no Covid benefits, data suggests
Two studies fail to find evidence to support claims supplements protect against coronavirus

The idea that vitamin D supplements can reduce susceptibility to, and the severity of, Covid-19 is seductive – it offers a simple, elegant solution to a very complex and lethal problem. But analyses encompassing large European datasets suggest the enthusiasm for the sunshine vitamin may be misplaced.

Two still to be peer-reviewed papers looked at the link between vitamin D levels and Covid-19 and both reached the same conclusion: evidence for a direct link between vitamin D deficiency and Covid outcomes is lacking.

Why do some COVID-19 patients infect many others, whereas most don’t spread the virus at all?
By Kai Kupferschmidt May. 19, 2020 , 5:25 PM
...
Most of the discussion around the spread of SARS-CoV-2 has concentrated on the average number of new infections caused by each patient. Without social distancing, this reproduction number (R) is about three. But in real life, some people infect many others and others don’t spread the disease at all. In fact, the latter is the norm, Lloyd-Smith says: “The consistent pattern is that the most common number is zero. Most people do not transmit.”

That’s why in addition to R, scientists use a value called the dispersion factor (k), which describes how much a disease clusters. The lower k is, the more transmission comes from a small number of people. ...

Estimates of k for SARS-CoV-2 vary. In January, Julien Riou and Christian Althaus at the University of Bern simulated the epidemic in China for different combinations of R and k and compared the outcomes with what had actually taken place. They concluded that k for COVID-19 is somewhat higher than for SARS and MERS. ... But in a recent preprint, Adam Kucharski of LSHTM estimated that k for COVID-19 is as low as 0.1. “Probably about 10% of cases lead to 80% of the spread,” Kucharski says.