Seasonal (‘flu’)

What is seasonal influenza?

Influenza or ‘flu’ is an infection caused by a . Flu is highly infectious .There are 3 main types of influenza virus: A, B and C. Most influenza infections occur during the winter months.

• Most outbreaks of influenza illnesses are caused by type A . These viruses are constantly changing so that different strains predominate from year to year. • Many people who say (or are told) that they have ‘flu’ in fact have a bad cold. • Usually what people call "gastric flu" is a ‘stomach’ (gastrointestinal) infection with another virus such as norovirus.

Who gets influenza?

Anyone can get flu. The amount of illness occurring each year varies and depends largely on how many people are susceptible to that particular virus, which depends on whether people have been infected or vaccinated against a similar virus in the past. If the new viruses differ greatly from previous ones, the population will not have much immunity. Some influenza viruses cause more severe illness than others. Hence in some winters people may have worse disease than in other years.

What are the signs and symptoms?

The most common symptoms of influenza are: • abrupt onset of • shivering • headache • muscle ache • dry

Flu usually starts suddenly with a high fever of 38.9-40.0oC (102-104oF). Headaches, chills and a dry cough are common, as are general muscle aches and pains, which can be severe. A stuffy nose, sneezing and a sore throat can also be present. The fever tends to decrease after the second day when nasal congestion and a sore throat become more noticeable. Some of those affected may also have nausea, or have vomiting and diarrhoea (up to 25%of children can have this). The acute illness generally lasts 2-7 days but tiredness can last 2-3 weeks.

Flu is usually a more severe illness than the , which is caused by other respiratory viruses. Cold symptoms are limited to the upper respiratory tract with runny nose, sneezing, watery eyes and throat irritation. The symptoms usually occur gradually and do not cause a fever or body aches.

What is the incubation period?

When a person comes into contact with the virus, it normally will take about two to three days to develop illness. How infectious is influenza and how is it spread?

Flu is most infectious from about a day before symptoms start until about 3-5 days later in adults. Children may continue to excrete the virus up to 9 days after onset.

Flu can spread very rapidly from person to person, both through the air from person to person by infected droplets from people with the infection by their and and by touch. It can be spread via hands by direct contact with saliva or indirect contact with respiratory fluid from an infected person when it gets on environmental surfaces e.g table tops, door handles and rails.

Limiting the spread of influenza

• Everyone with influenza-like illness should stay home and people should not return to school or work until they have recovered fully from their respiratory symptoms • Those with diarrhoea and vomiting symptoms as well should not return to school/work until 48 hours after the diarrhoea and vomiting has resolved.

Good hygiene is also vital to reduce the spread of flu, especially:

• Covering nose and mouth when coughing or sneezing, using a tissue when possible • Disposing of dirty tissues promptly and carefully into a rubbish bin • Washing hands frequently with soap and water to reduce the spread of the virus from hands to face or to other people • Cleaning hard surfaces (such as door handles) frequently using a normal cleaning product. The influenza virus can live on a hard surface for up to 24 hours and for around 20 minutes on soft surfaces • Avoiding touching the eyes, nose, or mouth as influenza can also be spread in this way

How serious is influenza? (Complications)

Most people recover completely from influenza in a matter of days or a week. For others, for example the elderly, those with other illnesses (e.g. chest / heart disease or diabetes) and newborn babies, flu can be a serious illness.

Serious illness from flu is usually not due to the virus itself, but to secondary bacterial infections causing lung infections (bronchitis and pneumonia) or to a worsening of under lying chronic medical condition such as heart disease. Protection against influenza

• There is a against seasonal flu. Each year a new vaccine has to be produced to protect against the flu viruses expected to be in circulation that winter. The effectiveness of the vaccine depends on how well the vaccine strains match the strains of flu that is actually circulating that year • The vaccine is very safe and side effects are uncommon and usually mild. The vaccine is given in the autumn before the flu season begins. It is not recommended for everyone, but it is advisable for, and offered to, those likely to be more seriously affected by flu (those with chronic heart, lung, kidney, liver and metabolic disorders; immunodeficiency; pregnant women or premature infants after the age of 6 months in the aforementioned risk groups, everyone aged 65 years and over and those in residential care accomodation. A GP/practice nurse will contact those who need the vaccine

• All the above named groups of people also need to have the pneumococcal vaccine, which offers protection against the commonest form of pneumonia and other conditions. This vaccine is given once only, except in special circumstances • It is recommended that seasonal flu vaccination is offered to certain health care workers and social service employees involved in the direct care of and/or support to patients/clients, plus main carers for elderly/disabled people • Children and fit adults under the age of 65 years who are not in one of the groups mentioned above are not recommended to receive the vaccine but can access it privately through some national pharmacy chains if wished.

How can you treat influenza?

• Most people do not need to see a doctor and would just require symptomatic relief e.g. rest and fluids • Influenza is caused by a virus so do not help unless there is a complication. In certain instances, however, an ‘antiviral’ medicine may be prescribed by a doctor (e.g. Oseltamivir)

Where can you get further information?

If you have any queries, or if institutions need to report influenza outbreaks/further advice on handling flu outbreaks, please contact the South West London Health Protection Unit on call team on 0344 326 2052.

There is also information on influenza at the following web sites:

Re influenza illness, from NHS Choices:

• http://www.nhs.uk/Conditions/Flu/Pages/Introduction.aspx

Re influenza vaccination, from NHS Choices:

• http://www.nhs.uk/Conditions/Flu-jab/Pages/Whyitshouldbedone.aspx

General information about influenza from the Health Protection Agency

• http://www.hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/SeasonalInfluenza/ InformationForThePublic/