This article answers these questions:

• What is seasonal flu?
• Is flu just a miserable short-term inconvenience?
• What are the symptoms?
• Who is most at risk of complications from flu?
• What precautions can we take?
• Can complementary health remedies help?
• What should we do if we get flu?
• Should we be worried about a flu pandemic caused by animal or bird flu affecting humans?

What is seasonal flu? 

Seasonal flu is an acute respiratory infection caused by influenza viruses which, in the UK, occurs mainly during winter. Most people recover from the fever and its other symptoms within a week without requiring medical attention. 

Flu is passed on when people breathe in liquid droplets containing the influenza virus which have been sneezed or coughed into the air by infected people, or when they touch objects contaminated with the virus.  

Is flu just a miserable short-term inconvenience?

For most people, in most years, the answer is yes, although the WHO reports that globally, seasonal influenza kills up to 650,000 people every year.

In England and Wales, in the year before Covid-19 the number of deaths from flu and its complication, pneumonia was 26,398 (plus 1,213 from flu alone). 

However, the monthly average number of people dying in the UK from seasonal flu and pneumonia, between January and August 2020 (i.e., during the first year of the COVID-19 pandemic), was on average one-third below the monthly average for the same months in the years 2015 to 2019 (i.e., before the pandemic) – suggesting that measures to protect against the transmission of Covid also helped protect against flu transmission.

Major outbreaks of flu

Then there are the exceptional years. More than 50 million people worldwide are estimated to have died from the so called ‘Spanish flu' in 1918; one million people died from Asian flu in 1957, and between one and three million died from Hong Kong flu in 1968. 

So, whether you’d like to avoid a week in bed feeling sorry for yourself, or avoid something potentially more serious, it is worth finding out more about flu, what causes it, what you can do to avoid getting it, and what to do if you do get it.  

What are the symptoms?

There are some clear differences between how seasonal flu viruses and the common cold viruses affect us.

Who is most at risk of complications from flu? 

Those most at risk of flu complications are:  

• older people (over 65)
• children under 5 years old (highest risk children are under 2)
• people with lowered levels of immunity as a result of disease or medical treatment
• people with underlying heart or respiratory complaints (such as asthma and COPD)
• patients with diabetes, serious kidney or liver diseases or who have had a stroke 
• People who are obese with a body mass index of 40 or higher.

Other risk groups include pregnant women, people in nursing homes and in other long-term health facilities, and certain ethnic groups. 

What precautions can we take? 

There are four main ways to avoid getting flu:

1. Get a flu vaccination every year.
2. Keep your immune system healthy.
3. Limit your contact with the flu virus.
4. Use a humidifier in winter. 

If you do get flu, prevent the spread of the virus to other people: Don’t travel (especially not on public transport), don’t socialise and don’t go to work when you have flu. Use a handkerchief to trap coughs and sneezes. Wash your hands often and well so that you don’t leave the virus on door handles or anything else other people might touch.

 1. Get a flu vaccination

‘Inactivated influenza vaccines can reduce the proportion of healthy adults (including pregnant women) who have flu and flu-like illness, but their impact is modest.’ That’s the conclusion from a 2018 review of the evidence in the Cochrane Database of Systematic Reviews. (This source of information is seen as providing particularly reliable reviews of research evidence.) 

As the flu virus can change quickly and easily, a new vaccine is prepared each year against three or four strains of flu that are expected to circulate in the coming winter. The decision about which flu strains will be used in the vaccine is made six months in advance. This allows time for vaccine production. Unfortunately, this also gives the virus time to change. This means that sometimes the vaccine may not be a good match for all the circulating flu strains.

Flu vaccines work better in some years than others. Between 2015 and 2020, it was estimated that the vaccines prevented between15% and 52% of flu cases. The effectiveness of the vaccine for 2019 to 2020 was 42.7%. 

The NHS recommends flu vaccination to help protect people at risk of flu and its complications, particularly those with long-term health conditions and/or over a certain age (currently 50 years).

A flu vaccination cannot guarantee protection against all strains of flu but, when the vaccine matches the predominant strain in a given year, it can have a significantly protective effect, which is particularly helpful for those most at risk. 

Research is currently underway by the National Institute of Allergy and Infectious Diseases in the US to develop a universal flu vaccine which would protect against multiple flu subtypes. The results of this research are promising. A successful universal vaccine would eliminate the need for an annual seasonal flu vaccine.

2. Keep your immune system healthy

Help your body fight the flu virus by eating a healthy diet, taking regular exercise, getting enough sunlight, getting enough rest and relaxation, maintaining a healthy gut and not smoking or drinking too much alcohol. 

3. Limit your contact with the flu virus  

There are several ways of reducing your exposure to the flu virus, all of which also apply to reducing your exposure to the COVID-19 virus:

• Limit contact with surfaces other people have touched, at home, at work and when travelling (including door handles).
• Wash your hands for at least 20 seconds with soap and warm water after touching such surfaces and especially before eating. If soap and water are not available use an alcohol hand gel.
• Keep your hands away from your nose and mouth.
• If you’re on public transport and someone near you is coughing and sneezing without covering their nose and mouth then move away.
• To help protect yourself and others, wear a face mask when in crowded places.

These measures are supported by our knowledge of how flu is transmitted from person to person. A systematic review of the evidence published in 2017 reported that regular hand hygiene provided a significant protective effect against the 2009 pandemic flu, whilst the use of facemasks provided a non-significant protective effect.

A systematic review in 2020 of 14 randomized trials of hand hygiene and face masks did not support a substantial protective effect on the transmission of the virus. The review also found that there was ‘limited evidence on the effectiveness of improved hygiene and environmental cleaning’. Having said this, the review recognised that some studies might have underestimated the true effect of hand hygiene because of the complexity of implementing the research studies and also considered studies using surgical masks, not the more protective N95 and FFP2 masks believed to be more protective during Covid. 

Surgical masks are loose-fitting and there is limited evidence for their effectiveness in preventing the wearer becoming infected. The main value is in reducing the transmission of virus to others. In contrast, respirators such as N95 and P2 masks, when fitted properly, protect the wearer from fine particles in the environment. However, a meta-analysis published in 2020 failed to show a lower risk of flu infection associated with the use of N95 respirators compared with surgical masks. This may be partly due to the low number of randomised trials included in the review. The discomfort of wearing respirators for long periods may also have been a factor. 

4. Use a humidifier in winter

Studies suggest it is not actually the cold of winter that causes the increases in flu but the lowered humidity. A 2018 study in Minnesota, US showed that, by increasing humidity in classrooms in a community school, there was a significant decrease in flu-positive samples (in the air and on surfaces) compared with rooms with normal humidity. 

Using a humidifier in the home during winter may therefore help provide some protection against flu by reducing the amount of time the flu virus can survive indoors.  

Can complementary health remedies help?

The US government’s National Center for Complementary and Integrative Health (NCCIH) reviewed the available research findings in 2016 and concluded: ‘No complementary approach has been shown to prevent the flu or relieve flu symptoms’. 

Oriental herbal medicine

A 2020 meta-analysis of 25 trials of oriental herbal medicine, however, showed a beneficial effect on flu symptoms (prevention of flu was not investigated). Oriental herbal medicine involves a holistic approach which commonly involves a mixture of several herbs containing multiple active ingredients.

When oriental herb medicines were combined with a standard anti-viral drug, the total effective rate (proportion of entirely recovered patients after a certain time period) was significantly increased compared to a single treatment with the anti-viral drug. In addition, the herbal medicine treatment significantly reduced the time taken for the fever to resolve compared to the anti-viral drug. This effect was enhanced when the herbal medicine treatment was combined with the drug.

This review suggests that oriental herbal medicine may be a useful addition to standard anti-viral therapy for flu symptoms. While these results are encouraging in principle, before this approach can be recommended for the UK, more information is needed on the specific herbal medicines researched, their dosages, the consistency of their effectiveness, and any potential side effects.

What should we do if we get flu? 

The best action you can take, if you’re not in a high-risk category, is to: 

• Stay at home and rest
• Keep warm
• Drink plenty of water to stay hydrated. 

Over-the-counter remedies to bring down your temperature, clear a stuffy nose and/or soothe a cough are seen by doctors as likely to relieve uncomfortable symptoms but not to shorten the time you have the flu. As always, read the label to check for possible side effects.

 

If you’re in a high-risk group (as described earlier in this article) or feel particularly unwell then check with your doctor.  

Should we be worried about a flu outbreak caused by animal or bird flu affecting humans?

A flu outbreak occurs when a novel flu virus emerges with the ability to be passed on between individuals who have no immunity against the virus. Circulation of some avian flu viruses in poultry are a public health concern as they can cause severe disease in humans. They also have the potential to change so that they can be more easily transmitted between individuals. Although this seems to have happened only in a few instances after prolonged contact, no sustained transfer of the virus between individuals has been identified.

Whether such flu viruses from avian, swine or other non-human sources currently circulating (known as zoonotic viruses) will result in a future outbreak is unknown. However, the possibility requires forward planning and continuous surveillance of human and animal populations by the WHO.

Human [zoonotic] infections are primarily acquired through direct contact with infected animals or contaminated environments. These viruses have not acquired the ability of sustained transmission among humans.                                                                                                                 WHO 2018

 

Conclusions 

Prevention is better than cure.

 

Although there is no single measure that is 100% guaranteed to prevent flu, these measures, when taken together, will significantly reduce your risk of getting flu: 

• Get a flu vaccination.
• Keep your immune system strong.
• Limit contact with surfaces other people have touched.
• Wash your hands before eating.
• Avoid other people’s coughs and sneezes.
• Use a humidifier in your bedroom in winter. 

Reviewed and updated by Barbara Baker, January 2022. Next review, December 2025.

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Other relevant articles on the Age Watch website:

• Diet: Vitamins and minerals
• Living longer: Look after your body
• Ageing: Ageing of the immune system (Immunosenescence)
• Mind: Resilience – is it important for your health?