Influenza or flu testing is used to decide whether your flu-like symptoms are due to the influenza virus or other causes, most often the common cold. It is mostly used in people who are at risk of developing severe complications from influenza such as the very young, the elderly, people from indigenous communities, those with lowered immune systems, and those who already have a chronic condition such as heart, lung, kidney disease or diabetes.
The test will show which of three possible viruses are present, influenza virus A, B or C, the most common being A. Identifying the type of virus will guide the choice of anti-viral treatment if this is needed. Some laboratories will also test for other similar flu-like viruses as part of the same test, such as parainfluenza, RSV or human metapneumovirus.
Influenza testing is also used to identify the virus type if there is an outbreak in a local community or in a place where many people are living together, such as a hospital, nursing home or school. This is so that measures can be taken to control and the spread of the virus.
Why get tested?
Flu is often confused with the common cold but they are caused by different viruses. Their symptoms can be similar and both can cause headaches, fever, chills, muscle pains, exhaustion, a stuffy or runny nose, sore throat, and a cough. However, the symptoms of flu are usually more severe and longer lasting and can lead to serious complications especially in the very young, the elderly, people from indigenous communities, those with lowered immune systems, and those who already have a chronic condition such as heart, lung, kidney disease or diabetes.
There are three types of influenza virus known as A, B and C, each of which regularly change or mutate to create multiple strains or sub-types. A is the most common and causes the most severe symptoms. Type B is less common with less severe symptoms, while type C usually causes only a mild illness that is similar to the common cold. Type A viruses are further categorised into subtypes based on two kinds of proteins on their surface: haemagglutinin (H) and neuraminidase (N). Significant alterations in these proteins occasionally results in a much more infectious or severe strain known as a pandemic strain, such as Swine Flu in 2009. Type B viruses are categorised into two lineages: Yamagata and Victoria.
Flu is easily spread, mainly through large particle droplets produced by sneezing and coughing. Droplets containing the influenza virus also settle onto surfaces and the virus can then pass from hands to the nose, mouth or eyes. If you have flu you can be infectious to others from 24 hours before your symptoms start until about one week after the start of symptoms. In previously healthy people, symptoms typically subside within five to eight days.
The flu test detects the genetic material of the virus, the RNA. It does this on a sample usually taken from the nose or throat. The accuracy of the test depends on having enough virus in the sample. The virus is only shed during the first few days that someone is ill and this is when the virus is at a level that can be detected.
Flu is a notifiable condition which means a doctor ordering a test and the laboratory performing the test are responsible for notifying the public health authorities. Your doctor may order a flu test to document an outbreak of flu in your local area as well as help diagnose your illness. If your infection remains unclear they may also order other tests or viral studies.
Having the test
Usually a nose or throat swab
If your flu test is positive, it will guide your doctor in deciding how to treat your illness including the use of anti-viral medications if you are at risk of serious complications. Generally, these medications need to be taken within 48 hours of the onset of symptoms in order to be effective at reducing the severity of symptoms. For otherwise healthy people, the treatment is to stay in bed and rest, drinking plenty of fluids, until the symptoms have receded.
A positive test result will also be shared with public health officials so that they can inform others in the community and take measures to limit the potential spread of the disease.
A negative flu test result may mean that you have something other than influenza, and more tests may be required. A negative test may also mean there was not sufficient virus in the specimen for it to be detected but this is less likely with newer, more sensitive detection methods.
Questions to ask your doctor
The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell themeverything you think might help.
You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.
Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:
Any more to know?
It is recommended that everyone over the age of six months is vaccinated against the flu. The vaccine cannot give you the flu because it contains deactivated virus. Vaccines in Australia are quadrivalent which means they act against four different types of flu. Each year they are redesigned to work against the strains that are circulating in the community.
The level of vaccine protection depends on several factors including the age and health of a person. Vaccine reduces the risk of someone under 65 getting the flu by between 59 per cent and 65 per cent. In older adults the level of protection is lower. For this reason there is a special adjuvanted vaccine for older people which has substances added to create a stronger immune response.
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