If you're feeling ill with a bad cough and temperature, you could just have a minor winter virus. Or could it be pneumonia?

Pneumonia is far more common than we think. The respiratory illness strikes around one in every 1,000 UK adults every year, killing 50,000 of them, and often during autumn and winter (pneumonia was the underlying cause in 19% of all excess winter deaths last year).

And if your health is already compromised, pneumonia can be the final straw - people with a heart condition who get pneumonia, for example, are four times more likely to have a heart attack or stroke.

Despite these figures, many of us remain unaware of the extent of the risk.

"People seem to put a great emphasis on protecting themselves against the common cold and flu, however, pneumonia accounted for the largest proportion of respiratory deaths last winter," says Dr Ben Marshall, a respiratory consultant at Southampton University Hospital.

"I've found there's still a lot of confusion between pneumonia and a 'really bad cold'. Symptoms are very similar, including cough, fever and shortness of breath," he adds. "However, pneumonia is usually much worse."

He believes some of the uncertainty stems from the fact that pneumonia can affect different people to very different degrees.

"That is the spectrum of the disease," he adds. "From a condition that can be managed in the home with antibiotics, to a condition that needs hospitalisation and sometimes intensive care." He points out that six to 10% of people with hospitalised pneumonia will die, particularly older people, who are much more vulnerable to chest infections.

"As hospital physicians, we regard pneumonia as serious when a patient's condition is bad enough to warrant admission to hospital, because we know it can kill."

WHAT IS IT?

Pneumonia is a viral, bacterial or occasionally fungal infection of the alveoli sacs (microscopic air spaces) in the lungs. The tiny air sacs become inflamed and swell with fluid, making it harder for the lungs to work properly. The body sends white blood cells to the lungs to fight the infection, but although this helps kill the germs, it can also make it harder for the lungs to get oxygen into the blood.

The most common type of pneumonia is pneumococcal, caused by the bacteria streptococcus pneumoniae, which can be vaccinated against. However, there are many other causes of pneumonia that can't be prevented with a vaccine.

Although some symptoms can be similar to those of other respiratory illnesses, like bronchitis (inflammation of the airways leading to the lungs), people will usually feel much more ill with pneumonia.

The same organisms can cause both conditions, but while bronchitis doesn't show changes on X-rays, pneumonia does. So X-rays, as well as examinations, are needed before a pneumonia diagnosis is made.

SYMPTOMS

Onset can be rapid and symptoms may develop over 24 hours, or come on much more slowly over several days.

They can be hard to differentiate from other chest infections, but are likely to include a cough, which could be dry or produce a thick yellow, green or brown mucus, possibly even blood-stained. There may also be chest pain.

Breathlessness, fever, sweating and shivering, feeling ill and losing your appetite are other common symptoms. Less commonly, there may be fatigue and headaches, and sometimes older people may become confused.

Pneumonia can be a consequence of a flu or cold infection, and can be caused by the same virus or a secondary bacterial infection. But sometimes, it can present on its own, with only the lower respiratory tract affected.

Dr Marshall says anyone who's alarmed because they're feeling ill, and have a new cough, worsening breathlessness and fever should see a nurse or doctor. Anyone who's extremely ill should call 999, as severe cases can quickly turn life-threatening.

WHO GETS IT

Over-65s and young children are more at risk, although of more than 170,000 adult hospital admissions due to pneumonia every year, more than one in five were in people under 65.

Smokers are also more at risk, as are people with existing medical conditions including heart disease, diabetes, and respiratory diseases such as asthma and COPD. In addition, those whose immune systems are compromised, such as cancer patients who've had chemotherapy, or transplant patients, are at higher risk.

If you've had pneumonia before, you're probably more likely to get it again, because there's a "chink in your armour" - something within your immune system that's let the illness take a hold once, may be vulnerable again.

"I tend to see pneumonia in my work colleagues when they're overworked, tired, under stress and they've not looked after their health," says Dr Marshall.

People in the at-risk groups are more likely to develop pneumonia complications too, including pleurisy (inflammation of the thin lining between the lungs and ribcage), and blood poisoning (septicaemia).

TREATMENT

Antibiotics will be given if the pneumonia is the most common bacterial type. However, antibiotics won't help treat viral pneumonia, and in these cases, antiviral medication may be tried, although it only works against certain viruses.

REDUCE THE RISK

"I find it particularly worrying that vulnerable people are still unaware they're even at risk, let alone that there are simple preventable measures they can take to protect themselves from pneumonia," says Dr Marshall.

"Look after yourself," he advises. That means eating a good, balanced diet, getting plenty of rest, avoiding stress where possible, and keeping well hydrated.

"Try not to be exposed to someone with a cough or cold, particularly if you have underlying health problems," he says. "So stay away from grandchildren who are coughing. And seek help if you do go down with anything. The earlier the presentation, the better the outcome."

There's also a pneumococcal vaccine available to at-risk groups, including babies, adults aged 65 or over, and children and adults with certain long-term health conditions, which helps protect against the most common cause of bacterial pneumonia. Also, t he flu vaccine will reduce cases of pneumonia associated with flu.

:: For more information about pneumonia, visit www.nooneexpects.co.uk