With its debilitating symptoms of aches, shivers and a pounding headache, a nasty bout of flu can leave even the toughest of us bedridden for several days. But while that used to be the only infectious virus to dread each year, now we have coronavirus to contend with, too. And by the looks of things, both viruses could make an unwelcome appearance this winter.
In August, it was revealed that “on the spot” swab DNA tests that can distinguish between Covid-19 and other seasonal illnesses - such as the flu - will be rolled out in care homes, schools and laboratories from next week. The health secretary Matt Hancock has said this move will be “hugely beneficial” over the winter months.
Experts are in agreement that chilly temperatures raise the risk of respiratory infections, heart attacks, strokes, and now, Covid-19. A study undertaken in July by researchers at Kings College London found that the virus is more severe in colder months than warmer ones, and that dry indoor air may encourage its spread.
With both illnesses sharing many of the same symptoms, but differing in severity, how can we spot the difference between the two?
When is flu season?
According to Bupa UK, people usually get seasonal flu between December and March, when the temperature begins to significantly drop. However, outbreaks can happen as early as October and late May.
The annual outbreak of respiratory syncytial virus (RSV) generally occurs even earlier than the flu, in October or November. This causes mild colds in people of all ages, but sometimes severe lung infections in the youngest and oldest among us.
What are the similarities between flu and Covid-19?
Both the flu and Covid-19 are contagious respiratory illnesses, and experts warn that their symptoms can be virtually indistinguishable.
While the main symptoms of coronavirus are a continuous cough and a high temperature, in recent months this has been widened to include a loss of taste and smell, a sore throat and chills, to name a few. Alongside this, a growing number of people have reported unusual symptoms, from post-viral fatigue to stomach pains. Even the loss of taste and smell isn’t unique to Covid.
"There’s a spectrum of different symptoms you can get with respiratory viruses. You really really cant tell which virus it is unless you get a PCR test,” says Professor Peter Openshaw, a Professor of Experimental Medicine at Imperial College London. "Both flu and Covid-19 cause malaise, fatigue, fever and shivering."
What’s even more confusing is that both illnesses can present as asymptomatic, meaning you could be spreading the virus without even knowing. A 2014 study carried out by Flu Watch found that 77 per cent of flu infections have no symptoms. Meanwhile, a study published in the Nature journal found that over 40 per cent of coronavirus cases are asymptomatic.
According to the Centers for Disease Control and Prevention (CDC), a fever, cough, shortness of breath, fatigue, sore throat, runny nose, muscle pain and body aches and a headache can all be symptoms of coronavirus and the flu. Some people report vomiting and diarrhea, but this is thought to be more common in children than adults.
The two could be similar in terms of transmission, too. According to the CDC, both Covid-19 and flu are spread through aerosol droplets that are made when people cough, sneeze or talk. These droplets can land in the mouth or noses of people nearby, and possibly be inhaled into the lungs.
However, Prof Openshaw warns that we can’t “assume that what we know about transmission of influenza automatically applies to Covid.
“Influenza tends to be more of a lung infection. It also replicates in the nose, but isn’t found so much in saliva and in spittle, so that may be a difference” he says. “Coronavirus also causes blood clotting effects, which are not seen in the flu.”
The only way to know for certain whether you have coronavirus is by receiving a diagnostic test.
How can you tell the difference between Covid-19 and the flu?
Without a test, it’s tricky, but there are things that you can note. The flu is caused by infection with influenza viruses, while Covid-19 is caused by a new coronavirus, SARS-CoV-2.
While both illnesses can cause a cough, the severity of yours might be a giveaway. “The cough some people describe with Covid can be particularly severe, almost as bad as the one people could get with Whooping Cough,” says Prof Openshaw. “With influenza, the cough tends to be relatively short lived.”
Indeed, another key difference to note is the severity of the two illnesses. While it’s unusual for flu to have long-lasting symptoms, many people experience a slow recovery from Covid; even mild cases have left some people feeling exhausted for weeks on end. The data around how many people will develop post-viral fatigue is uncertain, but its prevalence led the symptom to be included as a marker in the new Covidence UK study, which is looking into risk factors and long-term complications for Covid-19. Doctors and scientists are working to estimate the mortality rate of coronavirus, but at present, it is thought to be substantially higher than that of the flu.
According to Prof Openshaw, another giveaway could be whether flu is “circulating in your community.”
“We know that the likelihood of an illness being influenza depends on whether it is spreading. It’s much more likely to be flu if there is flu around,” he said.
Symptoms aside, Covi-19 and flu are different in the rate in which they can infect people. While a person can develop flu symptoms anywhere from 1 - 4 days after infection, a person infected with coronavirus typically develops symptoms five days after infection. However, they can appear as early as 2 days or as late as 14 days after the initial infection.
What should you do if you have symptoms of a cold?
While you might normally battle through a day at work with a cold, experts are in agreement that you should stay at home if you experience any symptoms, such as coughing, sneezing, a high temperature or a runny nose.
Dr Michael-fitzpatrick, the Telegraph’s GP columnist, previously told this paper that he would advise anyone with a "productive cough" or cold to stay at home. "The virus is transmitted by coughing and sneezing, droplet transmission. Anything that is likely to increase that risk of transmission, such as getting on public transport, should be avoided until the symptoms settle."
He says usually that would only be a period of two to three days for a regular cold or a viral infection. However, if you have coronavirus you must isolate for at least ten days - which is why it's important to get tested as soon as you can.
According to the NHS website, you'll usually need to self-isolate for 14 days if:
someone you live with has symptoms or tested positive
someone in your support bubble has symptoms or tested positive
you've been told to self-isolate by NHS Test and Trace
How are they treated?
"Feed a cold, starve a fever," the saying goes. And although unpleasant, it is generally agreed that cases of the flu can usually be treated with bed rest and plenty of fluids. However, if you have a severe infection, or you're categorised as high risk - in the case of flu, this includes elderly people, pregnant women and those who have asthma - doctors may prescribe an antiviral medication, such as Oseltamivir.
There are no drugs in primary care that clear a coronavirus infection. Experts recommend treating the fever with ibuprofen or paracetamol and plenty of fluids. A spoonful of honey can help to ease the pesky cough.
Unlike flu, there is currently no vaccine for Covid-19. However, in August scientists at Oxford University revealed that initial trials on 1,077 British adults found that the vaccine induced strong antibody and T-cell responses - a breakthrough in their research.
Should we be worried about flu season combined with a second wave?
The short answer is yes, although preparations are in place. A report published in July in the Academy of Medical Sciences warned that a resurgence of coronavirus could happen at the same time as a flu epidemic. Combined with the backlog of cases that the NHS are already battling, this could have a disruptive impact on the health service.
As part of “the biggest flu vaccination programme in history”, the Government has pledged to extent the eligibility to half the population, with 30 million people to be offered it this year. The plan has been widened to include everybody aged 50 to 64, a group thought to be more at risk of Covid-19 than younger adults; anyone shielding from Covid-19 and the people they live with; plus children aged 11 to 12 in their first year of secondary school.
That’s why it’s vital that anyone who falls into this category gets their flu vaccination, preferably from the beginning of October to the end of November.
There are some stumbling blocks. Now, patients have been told that it's likely they will have to wait until December for the jab - despite the fact the flu season may well start earlier, and amid fears of a second wave of Covid.
However, there is a silver lining. In the case of a winter lockdown, Prof Openshaw suggests that it may be harder for the flu virus to circulate, as fewer people will be coming into contact with each other.