At work, school and seeing friends: How to lower your coronavirus risk is an excellent new article on the New Scientist website, by Linda Geddes. Here we have some of the key points, though the whole article contains more detail, including workplace advice and is well worth a read.
THE coronavirus is still circulating yet many countries are taking steps to relax restrictions. If you have been asked to return to work or send your children back to school, how can you minimise the risk of infection to yourself and your family? Although there are still many unknowns about the virus, a growing amount of data on how it transmits and survives on surfaces can guide our decisions.
Keep Up to Date: We urge you to keep up to date with and follow your local guidelines. At the time of publishing, the guidelines for England, for example, were that anyone who is able to work from home should continue to do so, and that social visits should be limited to outdoor meetings with only one person at a time, at least 2 metres apart. Face coverings are advised in enclosed public spaces.
Avoiding infection – You are most likely to catch the virus by spending a long time near an infected person in an enclosed space. Researchers in Guangzhou, China, examined how the virus was transmitted between 347 people with confirmed infections and the people they had contact with. They found that the risk of the infection being passed on at home or by repeated contact with the same person was approximately 10 times greater than the risk of passing it on in a hospital and 100 times greater than doing so on public transport (medRxiv, doi.org/dwgj).
Outside the home, it is difficult to rank the relative risks, because environments vary so widely. However, “what we can say is that SARS-CoV-2 spread tends to be higher in communal areas where there are higher numbers of people passing through, or in areas where there is more physical engagement with the surroundings, for example door handles, desks and computer keyboards”, says Seema Jasim at the MRC-University of Glasgow Centre for Virus Research, UK.
Regular, thorough handwashing is still advised. It remains unclear how long the virus can survive and remain infectious on surfaces, but this is still thought to be a significant route of transmission. Because soap dissolves the virus’s fatty outer envelope, washing with water but no soap isn’t as effective. Alcohol hand rubs work, but are only necessary where there is no access to handwashing facilities, says Hosie.
Many people need or are being asked to travel to work, while in some countries exercising outdoors is permitted. So how can you minimise the risk in these circumstances?
“Whatever you’re doing outdoors, a 2-metre distance [from other people] should be enough,” says Lena Ciric at University College London. This is based on observations that large, virus-packed droplets from infected people tend to settle within a few metres of their source. “Smaller droplets, carrying fewer virus particles, can travel further but will be dispersed by air currents quickly,” says Ciric.
For getting to work, modes of transport that avoid other people, such as walking, cycling or driving in your own car, are the lowest risk. Car sharing may be the next safest option, assuming the driver is only giving lifts to a limited number of people. Taxis carry numerous passengers, so there is a risk of contracting the virus from surfaces like seats and door handles, or from the driver speaking, coughing or sneezing.
Public Transport: If these options aren’t available, that leaves public transport. People who travel on buses or trams during the winter flu season may be approximately six times more likely to develop a respiratory infection than those who don’t use public transport. If you do have to use it, there are things you can do to reduce your risk. The amount of time you spend near other transport users matters, says Anders Johansson at the University of Bristol, UK, who has modelled disease transmission in crowds and on the London Underground.
Besides trying to avoid the busiest stations and travelling times, it is worth considering the amount of time you spend navigating stations. Those with long underground passages – especially if they involve encountering people walking in the opposite direction – are best given a wide berth, and changing trains is also best avoided. These “usually mean you spend a longer time in the station, and are mixed together with people coming from various different parts of the city, if not the country”, says Johansson.
Face Coverings: Countries vary in their advice on face coverings when getting about. So far, the evidence suggests there may be a small benefit to wearing some kind of face covering, as these seem to lower the extent to which sick people spread the virus. In addition, face coverings may help protect vulnerable people who temporarily enter high-risk places like hospitals – but using medical masks can deprive healthcare workers of protective equipment.
Returning to school: From the data published so far, children seem less likely to acquire the infection than adults, and when they do, they are less likely to develop serious symptoms. Although a small minority do become seriously ill – including with a newly identified inflammatory syndrome – this is also true of many other viral illnesses.
There is also little evidence of schools and nurseries being major breeding grounds for infection, so far – although this is difficult to assess because many countries closed their schools relatively early in the pandemic. Some new reassurance comes from a report by the Children’s Commissioner for England, whose team has interviewed the managers of 44 nurseries that are attached to NHS hospitals and have remained open. Three have reported a confirmed case of covid-19 in a child and eight have reported a suspected case, but they have found no evidence of child-to-child transmission within the nurseries.
On the other hand, opening schools may prompt an increase in cases among the general population. Denmark, which reopened its primary schools on 15 April, did report an increase in the R number – the average number of people each case goes on to infect – from 0.6 to 0.9 in the following two weeks, but this has since dropped again.
Meeting up with friends and family: Evidence suggests that infection in the home, and between family members, is a significant source of viral transmission, and visiting people at home is still not allowed in many countries. Because transmission risk is probably much lower in the open air and can be reduced by maintaining a distance of 2 metres, it is probably safer to meet with people from outside your household in uncrowded outdoor spaces.
But what if you and a friend have both been strictly self-isolating? Would it then be safe to visit each other? Generally, you would expect any symptoms of an infection to have developed, and viral shedding to have largely ceased, 14 days after catching the virus. This may also be true of asymptomatic cases. “In both instances, at the end of the 14-day period they would be considered non-infectious,” says David Heymann at the London School of Hygiene & Tropical Medicine.
This may suggest that, if you have remained at home for the past 14 days and had no external contact, you are unlikely to be carrying the virus.
However, there have been reports of the virus persisting in the body for longer than two weeks. An analysis by US researchers calculated that 97.5 per cent of people who develop covid-19 symptoms do so within 11.5 days of exposure, but they estimated that for every 10,000 individuals quarantined for 14 days, about 101 of them would develop symptoms after this period (Annals of Internal Medicine, doi.org/dph3). A study in China reported incubation periods ranging from 0 to 33 days, and suggested an 18 or 21-day quarantine would catch far more cases (medRxiv, doi.org/dwgp).
For this reason, people should remain cautious about visiting other people, especially if they know they have been infected or have encountered other infected people. Additionally, if either of you are in groups deemed vulnerable to covid-19, Heymann suggests you both wear masks as an extra precaution when getting together.