How to winter-proof yourself against Covid

Winter is coming, and as the temperatures drop, and schools, universities and businesses reopen, coronavirus is resurging in the UK and across Europe.

Protecting ourselves in the colder months brings new challenges, as transmission rates are higher when people meet indoors. So how does Covid-19 behave in cold temperatures, and how can we keep it at bay this winter?

The virus thrives in chilly climates

Experts are undecided on whether coronavirus is seasonal but other respiratory viruses – like flu – tend to spread less in summer, says Ian Jones, professor of virology at the University of Reading. This is because they are transmitted via water droplets in breath, which dry faster in hotter, drier conditions with more UV light. The reverse is true in winter, so these viruses spread more quickly.

Some reports have suggested coronavirus thrives in colder climates, pointing to the fact that outbreaks have generally been more severe and more deadly in temperate regions such as Europe than in hotter, humid countries. One paper, analysing data from 7,000 patients admitted to hospital with Covid-19 in eight countries including the UK, found the mortality rate dropped by roughly 15 per cent for every one degree Celsius rise in temperature.  But experts believe it is behavioural change rather than cold weather that is behind the seasonal rise in cases. “The move to being indoors is likely to be the biggest factor driving an increase in transmission in the winter,” says microbiologist Dr Andrew Preston of the University of Bath.

How to meet safely inside

Indoor settings with poor airflow are considered one of the highest risk environments. Last week, the US Centers for Disease Control and Prevention updated its guidance to warn that coronavirus can “sometimes be spread by airborne transmission”, meaning particles could “linger in the air” in poorly ventilated indoor areas “for hours”.

Dr Michael Head, a global health expert at the University of Southampton, says: “The start of the chain of transmission is often from an indoor crowded setting such as a pub.” With evidence showing that air should be exchanged every six minutes to reduce transmission, it was reported that train operators in the UK are set to make it obligatory to have windows open on trains and for doors to be opened automatically for as long as possible at stations.

Choose a setting with good ventilation and social distancing in place, which isn’t too noisy – studies from London and Japan show places where people have to shout to communicate may have higher transmission rates.

Washing your hands, and wearing a face covering are still considered the best way to protect yourself indoors. Although face coverings are not mandatory outside in the UK – as they now are in Italy and some parts of France – they must be worn in shops, restaurants and bars.

As the rainy weather arrives, experts have warned that when masks get wet they  are less effective at filtering out bacteria and are more likely to expel droplets breathed out by the wearer, so it’s a good idea to keep a spare with you.

“Masks need to be changed regularly and this is particularly important to understand in damp and wet weather,” said Professor Tim Spector, leading epidemiologist and head of the Covid Symptom Tracker app, last week.

Covid-proof your home

Households mixing indoors seems to have been one of the key drivers of the spike in cases, which is why local lockdown rules prevent it. An Oxford University study found 40 per cent of coronavirus transmission happens before people develop symptoms, which means you could unknowingly be at risk whenever you meet others. Household meetings are a source of transmission because people spend a longer period together, and find it harder to social distance.

“In your home environment it is easy to let your guard down, but you should avoid being up close and personal with guests,” warns Dr Shaun Fitzgerald, Royal Academy of Engineering visiting professor at Cambridge University. You could space out your chairs to at least 1m apart – and go in the garden where possible. The recent rise in sales of outdoor heaters and fire pits suggest many are planning to continue alfresco entertaining through the colder months. Preston adds that wearing masks indoors when you have visitors and social distancing from them would minimise your risk. If that sounds too awkward, then keeping to the same group of six will also help, says Professor Keith Neal, an epidemiologist at the University of Nottingham. “If you meet the same five people every week and you only socialise with each other, then your risk is very different from meeting five friends who each socialise with five other different people and so on,” he explains.

The power of fresh air

“If you’re in a space with someone who is breathing out the virus, it will build up in the room over time unless there is ventilation,” says Preston. Not only does this build up increase your chances of catching Covid - it also raises the risk you’ll have a higher 'viral load', meaning you’re more likely to become seriously ill with it.  Ventilation reduces this risk. So to the government mantra “hands, face, space”, Fitzgerald adds: “open a window” – whenever there is more than one person in a room.

“In the colder weather you need to think proactively about leaving windows ajar, particularly if you have guests,” he says. To avoid freezing draughts, he advises leaving windows slightly ajar in different rooms with internal doors open to encourage airflow. Experts warn against using an electric fan inside in winter, however, as it could actually make things worse by blowing virus particles towards people.

Certainly, it’s looking like it’s time to dig out your warm jumpers. A King’s College London study suggests dry indoor air created by central heating could worsen the spread of coronavirus because it dries out the mucus barrier in our noses and throats that helps protect us against disease.

Should I buy an air purifier?

Air purifiers fitted with HEPA (high-efficiency particulate air) filters capture microscopic droplets of water or mucus, like those that carry Covid particles through the air – although none has yet been scientifically proven to remove the virus from the air.

Dr Gregory Poland at the Mayo Clinic in the US believes air purifiers could help but you must change filters regularly. And be careful about which model you choose. An investigation by consumer magazine Which? found several brands claimed their machines killed coronavirus despite having no evidence this is true. It also warns that the effectiveness of air purifiers can be limited by the size of the room and the age of the filter.

“Air purifiers wouldn’t be my first choice. If you can ventilate a room [such as by opening a window] that is what you should be doing”, adds Fitzgerald. Similarly, dozens of ‘UV sanitisers’ promising to keep your home germ-free are now being advertised online as indoor disinfectants. But, while hospitals use high-intensity UV light to safely sterilise equipment, anything marketed for use at home is unlikely to be effective at killing coronavirus, experts say.

“The strength of UV light [needed to disable viruses] is enough to blister your skin,” warns Neal. “You simply won’t be able to get the intensity you need with a domestic product.”

Vitamin D, and what to eat to boost your immunity

Evidence is mounting that vitamin D – the nutrient made in the body by sunlight – protects against Covid, or certainly reduces its severity.

A randomised control trial conducted in Spain on 76 patients with Covid found that giving a vitamin D supplement dramatically reduced the chance of needing intensive care. Now a cross-party group of MPs including Labour’s Rupa Huq and former Brexit secretary David Davis is urging the Health Secretary to provide vitamin D supplements on the NHS or launch a public health campaign on its possible benefits in the fight against coronavirus.

One in five Britons is thought to have low vitamin D levels, and even before the pandemic, Public Health England recommended we take a daily supplement between October and March.

“The evidence vitamin D improves your Covid outcome isn’t there yet, but I recommend people take low dose supplements throughout the winter to avoid vitamin D deficiency and to improve general health,” adds Neal. He warns you should not take more than the recommended daily dose – 10mcg for adults and children over the age of one – as too much can damage your kidneys and even put you at higher risk of becoming seriously ill if you get coronavirus.

Early stage research suggests antioxidant foods could help protect people from severe Covid symptoms, with one Indian study exploring the protective effects of nutrients like zinc, vitamin C, turmeric and probiotics. Following a balanced, gut-friendly diet with plenty of fruit and vegetables is one of the best things you can do to protect your general health this winter. And if you’re already thinking about a new year weight loss plan, don’t delay. Being overweight – and related conditions such as high blood pressure, diabetes and heart disease – are all major risk factors for coronavirus.