Influenza

Last updated: 11 June 2008

What is Influenza?

Influenza (or "the flu") is caused by infection with influenza viruses A , B and rarely C. It mainly affects the throat and lungs, but can also cause problems with the heart and rest of the body, especially in people with other health problems. Influenza viruses regularly changes, causing epidemics each winter in NSW. Every few decades a new type of influenza virus will emerge causing a severe and widespread epidemic (or pandemic).

What are the symptoms?

Symptoms usually occur one to three days after infection, and may include sudden onset of:

• fever
• headache
• muscle and joint pain
• sore throat
• cough
• runny or stuffy nose
• severe tiredness.

How is it spread?

• The virus is mainly spread from person to person through droplets after an infected person coughs or sneezes, or through touching (e.g., when a person shakes hands with another). It is easier to catch influenza in confined or crowded spaces.
• A person with influenza is contagious from the day before, until a few days after symptoms begin.

Who is at risk?

Anyone can get influenza. The elderly, people with other illnesses (such as heart disease, lung disease or diabetes) and small children are more likely to develop complications.

How is it prevented?

Vaccination
Anyone older than 6 months who wishes to avoid influenza should see their GP for a vaccine each year, well before winter begins. Influenza vaccination is especially recommended for:

• all adults aged 65 years and over
• Aboriginal and Torres Strait Islander adults aged 15 years and over
• adults and children older than six months with chronic diseases affecting the heart, lungs, or that require regular medical follow up
• persons with certain neurological conditions
• persons with immunodeficiency, including HIV infection
• residents of nursing homes and other long-term care facilities
• homeless people and those who care for them
• adults and children older than six months who live in a household with a person who fits into any of the categories above
• health care workers
• staff, volunteers and frequent visitors of nursing homes and long term care facilities
• people involved in the commercial poultry industry or in culling poultry during cofirmed avian influenza activity
• people providing essential services
• children (six months to 10 years) on long-term aspirin therapy
• people planning to visit parts of the world where influenza is circulating
• women who will be in the second or third trimester of pregnancy (even if already pregnant) between June and October.

• children up to the age of 9 years require two doses at least one month apart in the first year they are vaccinated.
• it will take up to two weeks for your body to develop immunity after vaccination. The vaccine is designed to match the viruses likely to be circulating that winter. In otherwise healthy adults, the vaccine usually provides about 70- 90% protection against infection for about one year.
• the vaccine is not recommended for some people, including those with allergies to eggs or who have had anaphylaxis following a previous dose of influenza vaccine or any vaccine component.
• side effects can include soreness at the vaccination site, fever, fatigue, and muscle soreness.
• the vaccine contains killed virus and so cannot cause influenza.
• people with a fever should delay vaccination until recovered.
• people who have previously had Guillain-Barré Syndrome should discuss vaccination with their doctor.

• 65 years or older
• an Aboriginal or Torres Strait Islander who is aged 50 years or older or aged 15 to 49 years with a chronic illness.

• stay at home until you are better
• cover your coughs and sneezes with a tissue and dispose of it in the garbage after use
• wash your hands with soap and running water for 10 seconds after coughing, sneezing or blowing your nose, and before touching other people or objects that other people might touch
• when visiting the doctor, call ahead to see if the doctor can put you in a separate waiting area and ask for a mask if you are coughing and have to wait near other people.

How is it diagnosed?

• Based on symptoms and examination, a doctor can diagnose an influenza-like illness.
• The diagnosis of influenza can only be confirmed by testing a sample of the fluid from the back of your nose and throat, or a sample of blood. These tests are usually only needed if the illness is part of an outbreak, is unusually severe or there are complications.

How is it treated?

• Fever, headaches and muscle pains can be relieved with paracetamol and rest.
• Medications for influenza (oseltamivir and zanamivir) can reduce the severity and the duration of illness if taken within two days of the first symptoms. They are available only on prescription from your doctor, and are sometimes in short supply.

What is the public health response?

Laboratories must confidentially notify cases of influenza to the local Public Health Unit. NSW Health also monitors the incidence of influenza in the community by tracking the number of people presenting to selected clinics with influenza-like illness, and the number of laboratory samples submitted to selected laboratories. Your local Public Health Unit can advise on control measures during outbreaks.

Futher Information

• Influenza in travel groups - Fact Sheet  /factsheets/infectious/travelflu_outbreaks.html
• Influenza in travel groups - PHU guidelines  /factsheets/infectious/travelflu_phu_guide.html
• NSW Controlling Influenza Outbreaks in Aged Care Facilities  /resources/publichealth/infectious/diseases/flucontrol_cdfs.html
• National Guidelines - Outbreaks in Aged Care Facilities  http://www.health.gov.au/internet/wcms/publishing.nsf/content/cda-pubs-other-flu_guidel.htm
• Influenza Report  /PublicHealth/Infectious/reports/influenza/2008/flu_20080829.asp