The annual flu season has brought even more risk to the coronavirus pandemic.
Hospitals across the UK are braced for an influx of patients and experts are warning the NHS could be under severe pressure this winter.
Yesterday, NHS CEO Sir Simon Stevens warned people are twice as likely to die if they go down with flu and Covid-19 at the same time.
Seasonal flu adapts into a new strain every year, meaning those most vulnerable to its effects are urged to get a flu jab annually to ward it off.
There are several similarities between Covid-19 and flu and both can be deadly – with the elderly and those with pre-existing medical conditions most at risk of the worst complications.
A link between seasonal flu and Covid-19 is that they are spread through droplets from the mouth or nose – hence the need for face coverings to reduce the spread.
But the rate of transmission is different, with the coronavirus being markedly more contagious.
And, while we are still learning about the new virus and how it affects some people more than others, scientists have identified some key differences in the symptoms, transmission and behaviour of Covid-19, compared to seasonal flu.
While the NHS urges people to get a flu jab to help ease the need for hospital treatment this winter, getting to know the differences between the usual illness and coronavirus will help you know what you may have caught and what action you should take.
Here are four ways Covid-19 differs from seasonal flu.
Scientists have not yet seen any human immunity to Covid-19
We do not yet have a vaccine for Covid-19 while each year the NHS offers a new flu jab which fights the latest seasonal strain.
Scientists say Covid spreads more easily than seasonal flu – and our lack of immunity is a major factor in its danger.
Airborne viruses expert Professor Linsey Marr, who lectures on civil and environmental engineering at US university Virginia Tech, warns a lack of Covid-19 immunity in populations leads to so-called “super-spreader” events.
Prof Marr explained to Huffington Post how more people in any given room are more likely to catch the coronavirus than they are the flu.
This is down to lack of immunity in the population rather than the nature of the virus itself.
So, as we already know, the race to find a vaccine for Covid-19 is of vital importance to fight the virus now and in the future, as we do with seasonal flu.
Some people who carry Covid-19 are ‘asymptomatic’ and do not display any symptoms
Covid-19 and the flu share several symptoms, with a high temperature and a cough among those.
Both could see you experience a dry cough and with Covid the cough would be persistent.
While people with the flu often experience headaches and a loss of appetite.
But scientists discovered early on in the pandemic that some people can catch and carry Covid-19 without showing any symptoms.
And this is another reason the coronavirus spreads more widely and more rapidly than seasonal flu.
If someone has no idea they have the virus – because there is no sign of any symptoms – then they will not self-isolate or avoid people, meaning they will be unwittingly spreading it.
Some scientists have even suggested that around 40 per cent to 50 per cent of people who catch Covid-19 are asymptomatic.
There are some cases of flu where people have shown no symptoms, but a key difference is that the ‘incubation period’ for Covid-19 is longer.
Prof Marr explained how the incubation period – the time between exposure to a virus and showing symptoms, or not – is up to 14 days with Covid, while people with flu tend to show symptoms withing three days.
This means the window for spreading flu to others and/or doing so unwittingly is much shorter.
Flu’s ‘viral load’ – the quantity of a virus in body fluid – does not tend to begin until symptoms are visible.
But with Covid-19, this could take up to a fortnight.
Higher viral spread
Prof Marr outlined how someone who has caught seasonal flu will on average spread it to 1.3 other people.
But with the coronavirus, this viral spread is almost double – to 2.5 people.
One example of a super-spreader event was in the White House Rose Garden, when top US scientist, Dr Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, revealed at least 11 people caught the bug.
Donald Trump’s team famously neglected to wear masks during the pandemic and at the September White House event we saw how Covid-19 can spread to more than 10 people at one event.
Dr Fauci said at the time: “We had a super spreader event in the White House, and it was in a situation where people were crowded together and were not wearing masks.”
And Prof Marr backs this up, highlighting how successful social distancing and proper use of face coverings makes it harder for Covid to spread at a rate of 2.5.
Covid transmission is different in kids compared to adults
Top boffins at Britain’s King’s College London found children display different Covid symptoms compared to adults, backing up other studies suggesting transmission of the virus is different for kids and grown-ups.
And the World Health Organisation has previously said “children are important drivers of influenza virus transmission in the community.”
It added: “For Covid-19 virus, initial data indicates that children are less affected than adults and that clinical attack rates in the 0-19 age group are low.
“Further preliminary data from household transmission studies in China suggest that children are infected from adults, rather than vice versa.”
The WHO also reminded that, when it comes to seasonal flu, children are known to be more at risk of developing severe infections.
Children under the age of 6 months are at the highest risk of severe complications from the flu due to their immune systems being less developed and more fragile, and the fact they are too young to be given the flu jab.
Pregnant women, the elderly and those with pre-existing health conditions are also more at risk from the flu – as they are with Covid.
But for kids at least, with the coronavirus, it seems the kids are alright, as the main risk is seen in the elderly and those with pre-existing health conditions.
The WHO added: “For Covid-19, our current understanding is that older age and underlying conditions increase the risk for severe infection.”