As winter approaches, so too does the season of influenza and the common cold - two viruses which we often confuse but which need to be treated differently, writes Nicole Matthews
It's October and the call of winter has started in the office, on the street and in schools. The cough, cold and runny nose - known as the common cold but described by many as the flu - is coming and there is little or nothing anyone can do to avoid it.
Influenza is defined by the World Health Organisation (WHO) as "a virus that attacks mainly the upper respiratory tract - the nose, throat and bronchi and rarely also the lungs".
It generally lasts for one week and is characterised by a high temperature, headache, cough and sore throat - many of the symptoms of the common cold.
Dr Andrew Coady, a GP in Tallaght, Co Dublin, says that while there are similar symptoms between the common cold and influenza, in reality they are very different.
"Both have very similar characteristics such as a cough, sore throat, aches, pains and tiredness, but influenza is much more severe, so the difference is in severity rather than symptoms," he says.
Dr Peter Harrington, a member of the National Immunisation Advisory Committee, says the number of patients with influenza is much lower than the number of people who describe their illness as the flu.
"For many Irish people, the flu is everything from a head cold to a cough to a runny nose, but the vaccine is specifically for influenza, which is a very debilitating illness. Last year I had between four and five cases of actual influenza," says Harrington.
There are three types of influenza, with type A and B causing the majority of infections and C being a rare infection in humans. Influenza A has two subtypes which are important for humans: A(H3N2) and A(H1N1), of which the former is currently associated with the most deaths.
Three times in the last century the influenza A virus changed genetically, causing three worldwide pandemics which not only affected the very young and old, but also healthy and fit young people.
The worst of these was the "Spanish Flu", which killed at least 40 million people worldwide between 1918 and 1919.
The last influenza epidemic in Ireland was in 1999-2000. According to Dr Suzanne Cotter, a specialist in public health medicine with the Health Protection Surveillance Centre (HPSC), influenza was not a notifiable disease in Ireland until 2004 when legislation was changed. Because of this, there is no data available before that date to measure the magnitude of the epidemic.
Most recently, limited outbreaks of a new influenza subtype, A(H5N1), which is directly transmitted from birds to humans and is known as avian flu, occurred in Asia between 1997 and 2003.
The influenza vaccine or flu shot is recommended for everyone over 65 years of age and, according to the HPSC, is 70-90 per cent effective in protecting against flu.
"Diabetics and people with heart or lung disease or moderate to severe asthma should also get the flu shot as they may be more susceptible to picking something else up with the flu such as pneumonia," says Harrington.
The flu shot begins protecting people two weeks after they receive it, so it is recommended that it is given in October to protect against the oncoming flu season.
"The overall uptake of the flu vaccine for 2004-2005 in people over 65 was approximately 61 per cent," says Cotter.
Coady says that because the influenza virus changes and mutates constantly, the vaccine also changes, which is why people must get it annually.
"There is an antigenic shift and drift where the WHO will analyse what types of influenza are around and which are most likely to take hold in certain regions, and then the vaccine will be developed on the basis of that each year," says Coady.
The flu vaccine is not a live vaccine and cannot cause influenza as is often thought. There is no vaccine against the common cold and the flu vaccine will not protect against it.
Cold viruses are grouped into eight segments, with the most common being rhinoviruses, which are responsible for almost half of all colds, and coronaviruses, which triggered SARS and account for approximately 15 per cent of colds.
According to Coady, the reason for an increase in infections entering winter is not the cold weather.
"The real reason for peaks in infection is that people are indoors more, sharing smaller spaces, and children are back in school inhaling and coughing droplets into the air, so there is closer contact than in the summer when more people are outdoors," he says.
So is there any way of protecting yourself from the common cold?
Harrington says that building up your general immunity is the most important method of self-protection.
"To protect against influenza, general immunity is very important, so eight hours' sleep per night, exercise and a good diet is key," he says.
Anne Harty, manager of the Jan De Vries clinic in Dublin which specialises in alternative healthcare and homeopathy, says that a good, balanced diet should be enough to boost immunity.
"Garlic in food and drinking water breaks down phlegm. Onion and beetroot are very good blood tonics and homemade vegetable soup is very good for the body," she says.
Harrington also recommends that people going to their GP for the flu vaccine should ask about the pneumococcal vaccine, which protects against pneumonia.
"It is a single-shot vaccine so it's only given once in a patient's life and especially for those over 65," he says.
"We offer it to all who get the flu vaccine so patients should check with their GP."