How the virus behaves

sir – A teachers’ union asserts that school exercise books will have to be “sanitised”, and marking them “will not be safe” (report, May 22).

As a consultant pathologist in a large NHS hospital, I have to read medical records of patients who have died from Covid-19. Initially these records were “quarantined” for two weeks after death. Then we started to receive them after 24 hours.

When I questioned this change, the hospital’s consultant virologist leading on Covid cited new scientific evidence showing that the virus survives for no more than a few hours on paper and cardboard. He referred me to scientific papers in reputable medical journals. I trusted him and so far have not caught the virus. So I believe he is right.

If medical records probably exposed to an aerosol of virus particles are safe to handle after 24 hours, then marking schoolbooks is surely safe. (The same applies to the Church of England’s startling prohibition of the handling of bibles, prayer books and bell ropes.)

Following the scientific evidence should mean changing your opinion when new evidence emerges. Of all people, teachers should know that.

Professor Peter Furness

Whissendine, Rutland sir – A colleague and I have modelled Covid-19 cases and deaths in 20 European countries, including the UK, against about 20 factors such as heart disease, obesity, smoking, exercise, pollution and latitude, as well as vitamin D levels.

For Covid-19 cases, the main factors are cardiovascular disease, vitamin D levels (which increase immune response, as pointed out in the Telegraph), latitude (as the virus prefers cold) and the proportion of African/afro-caribbean people in a population (also pointed out in the Telegraph).

For Covid-19 deaths, the main factors are population density (related to distancing), the proportion of vegetarians and the proportion of African/afro-caribbean people.

These factors account for about 80 per cent of the variation in cases and deaths in these 20 European countries.

Errors made by the Government (as by numerous other governments) may have affected the disease’s progress, but our results show that demographic factors outside the Government’s immediate control play a major part.

Professor John Dearden

Helsby, Cheshire