It is said – often by our mothers – that we are looking a bit ‘peaky’ or under the weather even when we do not notice ourselves.
Now researchers have discovered that humans have an ability to pick up the subtle signs that show someone is sick within minutes of them getting an infection.
Some signs of sickness are obvious– such as a violent cough, or the spots on the face in measles.
These are obvious enough to ensure the ill person gets a wide birth.
But in an illustration of the amazing power of the human brain, a glance of a few seconds was enough for observers tell if people had just caught a nasty bug.
Researchers found that certain almost imperceptible facial changes announce we are poorly – and these can be detected by people with no medical training.
Researchers have discovered that humans have an ability to pick up the subtle signs that show someone is sick within minutes of them getting an infection
The cues are that we become slightly paler, our faces more swollen, our eyes more droopy, our eyes redder and a more tired appearance.
And of these, a paler face and droopier eyes were the cues that tell others most that we are getting sick.
The findings could one day be used by Artificial Intelligence systems to look at our faces and warn us if we are about to get ill, researchers said.
The researchers also say it helps explain a common finding in psychology that people who look tired are less popular and attractive.
This may be because they look similar to someone who is ill – and we are shunning them to protect ourselves from disease.
To see if humans can visually detect the early stages of sickness, researchers injected volunteers with two solutions.
One contained harmless sugar water. The other contained a chemical compound extracted from E Coli bacteria intended to make the recipient feel ill.
‘AUSSIE FLU’ STARTS TO TAKE HOLD
The dreaded Aussie flu outbreak expected to be the worst in 50 years is continuing to wreak havoc on Britain, official figures show.
Some 1,649 people were struck down with flu in England and Wales as temperatures plummeted over the week of Christmas.
The Public Health England data shows cases have soared by 48 per cent in a period of seven days – and are higher than previous winters.
It comes amid anticipation of the worst winter on record for the NHS – despite last year’s being branded a ‘humanitarian crisis’ by the Red Cross.
Doctors have described corridors overflowing with patients and ambulances being forced to queue outside A&E as the winter flu season begins to take hold.
The rocketing number of flu cases has been put down to a surge in two aggressive subtypes attacking the population simultaneously.
One includes the so-called ‘Aussie flu’, a strain of influenza A which wreaked havoc on hospitals in Australia during the country’s winter.
The H3N2 subtype triggered two and a half times the normal number of cases in Australia. Britain’s flu season tends to mirror what has happened there.
Experts fear the virulent flu strain, which has now reached the UK, could prove as deadly to humanity as the Hong Kong flu in 1968, which killed one million people.
Usually, just one subtype, either influenza A or B, is responsible for the majority of cases. It spreads much easier in the cold weather.
The compound contained is a complex sugar used by bacteria to build their cell walls.
When detected in our bodies, our immune system sounds the alarm and prepares to defend the body from attack – triggering inflammation in the infected area.
After two hours, pictures were taken of the faces of both those given the sickness causing jab, and the others receiving the harmless jab.
These pictures were shown to observers for a few seconds.
Despite the pictures looking similar, observers were able to detect in 81 per cent of cases – 13 out of 16 individuals – as being sick better than chance.
The 16 volunteers were all white, non smokers, non-obese, moderate drinkers aged between 19 and 34.
The authors said: ‘These results demonstrate that untrained people can, above chance level, identify acutely sick individuals from merely observing a photo for a few seconds.’
Lead researcher John Axelsson of the Stress Research Institute at Stockholm University and colleagues said previous research has found that people showing ‘sickness behaviours’ such as coughing respond with disgust and anxiety.
He said what is less well known is how well we can detect sickness from observing human faces in the early stages of infection.
The study said that unlike previous research: ‘The photos here were taken in an experimental setting with neutral facial expressions only two hours after onset of a systemic inflammation.
‘This supports the notion that humans have the ability to detect signs of illness in an early phase after exposure to infectious stimuli.’
The researchers said people are likely to have developed the ability as it is ‘particularly beneficial to identify sick individuals at an early stage of sickness when risk for contagion is high’.
Professor Axelsson said: ‘This is just a first step. Personalised artificial intelligence will be able to pick up these signs in the future.
‘You will look in an app, which will say, “Maybe you have an infection today.”‘
The research was published in Proceedings B, a Royal Society Journal.