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Winter viral illnesses

Michael Carter, Greta Hughson
Published: 10 October 2012

This factsheet provides basic information on common winter viral infections: colds, flu, pneumococcal disease and winter vomiting bug. During the winter months most people, regardless of their HIV status, can expect to become unwell with colds or flu. On the whole you can expect to recover completely in a few days without any medical attention and with no lasting ill-effects.

Information is also included on secondary bacterial infections that can develop after having a cold or influenza, and the rare allergic reaction to some anti-HIV drugs, the symptoms of which can resemble flu.

The common cold

More than 200 viruses are known to cause common colds. The cold-causing virus can enter the body through the mouth or nose and by hand-to-hand contact and infects the upper respiratory tract. Cold symptoms usually start two or three days after infection and often include a runny nose, sneezing, a sore throat, a mild cough and headache. Temperature may rise slightly, but rarely above 38°C. As the body fights back against the virus causing the cold, the inside of the nose may start to swell and hurt, the nose run more and the skin feel sensitive.

Influenza (flu)

Influenza (normally just called flu), is also a viral illness that infects the respiratory tract. People with HIV are recommended to have an annual vaccination against flu. You can find out more in NAM’s factsheet Influenza ('flu').

Pneumococcal disease

Pneumococcal disease is caused by a bacterium called Streptococcus pneumoniae (pneumococcus). It is a common cause of illness, especially in people with HIV. A vaccine is available. You can find out more in NAM’s factsheet on Pneumococcal disease.

Winter vomiting bug (Norovirus)

This illness involves nausea, vomiting, and diarrhoea. It is very contagious and can rapidly spread through families, schools and even hospital wards. It is caused by Norovirus and people usually get better within 48 hours.


Antibiotics do not work against colds, flu or winter vomiting disease. The best treatment is likely to consist of rest, taking paracetamol or ibuprofen to help reduce temperature or discomfort, and drinking plenty of water and fluids, particularly if you are being sick frequently or have diarrhoea.

Avoiding winter infections

Hand washing reduces the chance of picking up a winter viral infection. If you have a cold or cough then use a tissue and throw it away. Try to avoid spending too much time in the presence of people with sniffles, sneezes or coughs. Although some people find that some herbal or vitamin remedies either help them avoid catching colds and flu or recover quicker, there is no research evidence that these products are effective.


Vaccinations against the flu and pneumococcal disease are available from GPs, usually from September until early November, and one of the groups of people in the UK who can receive these free on the NHS are people with HIV. Flu vaccines are particularly recommended for people with a high risk of lung or heart disease. In recent years a vaccine against H1N1 (swine flu) has been included in the seasonal flu vaccine.

Secondary infections

Colds and flu do not 'turn into' bacterial infections like pneumonia, but some people do develop secondary bacterial infections, often in the sinuses, ears or lungs that require medical attention and antibiotic treatment.

These may be more likely to occur in people with weakened immune systems. If your symptoms last for more than a few days, become worse or if your temperature increases above 39°C you should see your doctor.

Hypersensitivity (allergic) reactions to anti-HIV drugs

A dangerous allergic reaction to the anti-HIV drug abacavir (Ziagen, also in the combination pills Kivexa and Trizivir) has symptoms which resemble severe flu.

Although this reaction can occur in people taking abacavir at any time, it is most likely to happen in the first few weeks of treatment.

Allergic reactions that resemble some symptoms of flu have also occurred in people taking etravirine (Intelence), nevirapine (Viramune, Viramune prolonged-release) and raltegravir (Isentress).

Symptoms include fever, rash or blistering of the skin, extreme tiredness and muscle or joint pain. If you think you are experiencing a reaction to any of these anti-HIV drugs, you should see your HIV clinic immediately (or A&E if out of hours).

You can find out more about these very rare allergic reactions in NAM's patient information booklet Anti-HIV drugs.

Contact NAM to find out more about the scientific research and information used to produce this factsheet.

This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.