The beginning of October marks the start of the annual 'flu season' which will continue through to April 2011. Flu epidemics usually occur in the colder months of the year but, as seen in the 2009 pandemic, they can occur in other months too.

As announced by the Department of Health last week, the annual seasonal flu immunisation campaign will this year include pregnant women for the first time, along with everyone aged 65 or over, people who live in residential or nursing homes, people who are carers and those under 65 with underlying health conditions such as heart problems, diabetes or asthma.

As the Influenza H1N1 2009 virus (formerly known as 'swine flu') is now becoming one of the group of seasonal flu viruses circulating around the world, the World Health Organization has recommended the routine flu vaccine include a H1N1 2009 component so that people who are vulnerable are protected against all the circulating strains. A similar process was followed after the last pandemic in 1968 when the new H3N2 component was added to the seasonal vaccine.

Throughout the flu season, the HPA will use a comprehensive set of surveillance schemes to monitor the levels of flu activity in the UK population as well as carrying out virological testing of the virus strains. This testing is carried out to assess which strains of flu viruses are circulating and the levels of each.

These surveillance systems include data from GP practices across the country on the number of consultations for flu-like illness as well as the number of phone calls received by NHS Direct from people reporting symptoms.

The HPA also has a network of labs around England which test and report on the occurrence of the flu viruses in samples taken from patients in GP surgeries and hospitals across the country.

Professor John Watson, head of the respiratory diseases department at the HPA, said: "We can never predict what will happen in any flu season but we will remain vigilant and assess the situation as more information becomes available from our surveillance systems and from the virus samples.

"We have been keeping a close eye on the flu season in the southern hemisphere where there has been a mixed pattern of flu activity with some countries seeing moderate levels of H1N1 2009 activity and others seeing relatively little. We should expect that flu viruses will circulate this winter and it remains important that everyone who is in an at-risk group receives their flu jab."

For the majority of people, flu is an unpleasant, but not life-threatening illness. But it can be dangerous for certain groups in the population, such as the elderly, those with underlying health conditions and those who have a weakened immune system. Pregnant women were disproportionally affected by the H1N1 2009 flu strain of the virus so experts have recommended they be included in the groups routinely offered the seasonal flu jab this year.

During the first part of the 2009 pandemic, the HPA provided weekly estimates of the numbers of cases of H1N1 2009 in each region of England. During the 2010/11 flu season, the HPA will return to the pre-pandemic routine of reporting consultations for flu with GPs. These are expressed as a rate per 100,000 of the population and not estimated numbers of cases of flu.

Data on patients hospitalised as a result of flu were also collected during the pandemic and a revised version of this system will continue this winter to monitor the occurrence of more severe disease.

Professor Watson added: "As in previous seasons we will produce our weekly flu report which will detail the viruses that are circulating together with information on the levels of influenza illness in the community. This helps to inform health professionals of both the types of viruses and burden of disease circulating. If levels of flu reach a certain point it triggers a notification that doctors will be advised to use antiviral drugs for the prevention or treatment of flu in patients who are at higher risk of developing complications."

What is flu?

Flu is a viral disease and symptoms can include a headache, fever, cough, sore throat, and aching muscles and joints.

What should you do if you get flu?

If you do get flu this year, our advice is to stay at home, rest, drink plenty of fluids and use over-the-counter remedies if they make you feel more comfortable.

Can you stop getting flu?

The best ways to decrease your chances of getting flu is to practice regular hand washing and good respiratory hygiene - covering mouth and nose when coughing or sneezing, using tissues and disposing of them correctly.

What viruses cause flu?

There are two main types of viruses that cause flu, influenza A and influenza B (Influenza C is an uncommon type that infrequently causes infection). Influenza A is usually a more severe infection than influenza B.

What are the strains in this year's flu jab?

The strains chosen for inclusion in the annual three part vaccine are chosen by the WHO as the seasonal strains that are most likely to be circulating. It is likely there will still be a substantial amount of H1N1 2009 circulating so the vaccine for that strain has been included.

The seasonal 'trivalent' vaccine will include:
A/California/7/2009 (H1N1)-like virus (This is the full name of the swine flu virus)
A/Perth/16/2009 (H3N2)-like virus
B/Brisbane/60/2008-like virus

More information about seasonal flu can be found on the HPA website.

Information on the seasonal flu jab from the Department of Health can be found here.

Source:
Health Protection Agency