Having a cold blocks you from catching the flu © Getty Images

Having a cold blocks you from catching the flu

It's not clear whether colds could also stave off infection with COVID-19.

Rhinovirus, a virus that causes the common cold, may be able to prevent the flu virus from infecting airways, a new study suggests. Researchers say the rhinovirus could jump-start the body’s antiviral defences, providing protection against the flu.

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The findings help answer a mystery surrounding the 2009 H1N1 swine flu pandemic, when an expected surge in swine flu cases never materialised in Europe during autumn.

A Yale University team led by Dr Ellen Foxman studied three years of clinical data from more than 13,000 patients seen at Yale New Haven Hospital with symptoms of respiratory infection. They found that even during months when both viruses were active, if the common cold virus was present, the flu virus was not.

Dr Foxman, assistant professor of laboratory medicine and immunobiology and senior author of the study, said: “When we looked at the data, it became clear that very few people had both viruses at the same time.”

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But she added that it is not known whether the annual seasonal spread of the common cold virus will have a similar impact on infection rates of those exposed to the coronavirus that causes COVID-19.

Dr Foxman said: “It is impossible to predict how two viruses will interact without doing the research.”

In order to test how the rhinovirus and influenza virus interact, the researchers created human airway tissue from stem cells that give rise to epithelial cells, which line the airways of the lung and are a chief target of respiratory viruses. They found that after the tissue had been exposed to rhinovirus, the influenza virus was unable to infect the tissue.

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“The antiviral defences were already turned on before the flu virus arrived,” Dr Foxman said.

According to the study, published in The Lancet Microbe, the presence of rhinovirus triggered production of the antiviral agent interferon, which is part of the early immune system response to invasion of pathogens.

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The researchers are now looking at whether introduction of the cold virus before infection by the COVID-19 virus offers a similar type of protection.

I’m addicted to the gym, but I have a cold. Can I still exercise?

A good rule of thumb is the ‘above-the-neck test’, which says that if your cold symptoms are all in your head – such as a runny nose, sneezing or a sore throat – then it’s safe to do some light to moderate exercise.

Last year, health scientists at the University of Bath published a paper arguing that even vigorous exercise is okay, citing evidence that it can boost immune system functioning. Take it slowly, though, and tone down your session if you’re feeling weak or uncomfortable.

And if you have below-the-neck symptoms such as a high temperature or chest congestion, it’s best to rest up completely, as exercising will raise your temperature even higher and stress your body, leaving you feeling rotten.

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