Flu test: Detecting flu viruses

Got flu symptoms? Wondering if you need a flu test? Here's how a flu test might sometimes help.

In most cases, a doctor can diagnosis the flu based on flu symptoms, especially when these symptoms occur during the peak flu season. But sometimes your doctor may want to perform an influenza test to be sure the influenza virus is responsible for your symptoms and not another health problem.

Why is a flu test helpful?

Seasonal influenza epidemics are responsible for millions of cases of severe illness and between 250,000 and 500,000 deaths worldwide each year. According to the NHS in the UK around 600 people a year die from seasonal flu. This rises to around 13,000 during an epidemic. However, influenza viruses can also cause large pandemics, such as the one that occurred in 1918 and killed at least 20 million people. If there is a risk of a serious pandemic, your doctor may be nominated to help monitor its progress by taking tests.

How does a flu test work?

First, your doctor will take a sample from the back of your throat or nose. To collect this sample, the doctor will use a cotton-tipped wooden stick and will simply rub the cotton tip at the back of your throat or inside your nose. The doctor will then seal the sample in a packet and send it to the lab for testing.

What does the flu test detect?

Some flu tests detect only influenza A virus. Others can detect both influenza A and influenza B viruses.