flu specialist tests overview

Overview

This article explains the specialist tests that healthcare providers use to diagnose influenza, commonly called the flu. The flu is a contagious respiratory infection caused by influenza viruses. While many people recover at home, tests can help confirm the flu, especially when symptoms are severe or you are at higher risk of complications.

Influenza is very common, especially during the winter months. Many people get the flu each year, but only a small number require specialist testing.

Anyone can get the flu, but it spreads easily in communities. People more likely to need flu tests include young children, older adults, pregnant women, and those with long-term health conditions like asthma, diabetes, or heart disease.

Symptoms

Common symptoms

• Sudden high temperature (fever) or feeling feverish
• Muscle or body aches
• Feeling very tired or weak
• Dry cough
• Sore throat
• Runny or stuffy nose
• Headache

Symptoms in children

• All the common symptoms, plus possible nausea, vomiting, or diarrhea
• Fussiness or not wanting to eat
• High fever that may cause febrile seizures (convulsions)

Symptoms in older adults

• Typical flu symptoms may be less obvious; sometimes only confusion, weakness, or a worsening of existing health problems
• Lower or no fever
• Loss of appetite
• Dizziness or increased risk of falls

Causes

Main causes

• Influenza viruses, mainly types A and B, spread through droplets when an infected person coughs, sneezes, or talks.
• Touching surfaces contaminated with the virus and then touching your mouth, nose, or eyes.

Risk factors

• Being younger than 5 years or older than 65
• Pregnancy or up to 2 weeks after giving birth
• Having a chronic medical condition (e.g., asthma, diabetes, heart disease, weakened immune system)
• Living in a care home or long-term care facility
• Not getting the annual flu vaccine

When to see a doctor

See a doctor urgently if:

• If you have any emergency symptoms listed above, call your local emergency number immediately.
• If you are at high risk of complications and have flu-like symptoms, see a doctor as soon as possible.

Book a routine appointment if:

• If your symptoms are mild but you are unsure whether you have the flu or another illness.
• If you need a note for work or school, or you want to discuss the flu vaccine.

Diagnosis

A doctor or nurse will ask about your symptoms and do a physical exam. If they suspect the flu and need to confirm it – especially during flu season or for high-risk patients – they may use a specialist test.

Tests that may be done

• Rapid influenza diagnostic tests (RIDTs): A swab from your nose or throat gives results in about 15 minutes. These are very helpful for quick decisions but may miss some cases.
• Rapid molecular assays: Also use a nasal swab and give results in 15–30 minutes. They are more accurate than RIDTs.
• Reverse transcription polymerase chain reaction (RT-PCR): This is the most accurate test for the flu. It detects the virus's genetic material and takes a few hours to process. It is often used in hospitals or during outbreaks.
• Viral culture: A swab sample is sent to a lab to see if the flu virus grows. It can take 3–10 days and is less common now, but useful for tracking new strains.

What to expect at your appointment

A healthcare provider will gently insert a small, soft swab into your nostril or the back of your throat for a few seconds. It may tickle or cause brief discomfort. The sample is then sent to a lab or tested right away. Results may be available in minutes to hours, depending on the test.

Treatment

Treatment for the flu focuses on relieving symptoms and preventing complications. Most people recover without any specific medical treatment. If you are at high risk or have severe illness, a doctor may recommend antiviral medicines, which work best if started within 48 hours of symptoms. Antibiotics do not work for viral infections like the flu.

Self-care at home

• Rest as much as possible to help your body fight the infection.
• Drink plenty of fluids like water, clear soups, or oral rehydration solutions to prevent dehydration.
• Use a cool-mist humidifier or take a steamy shower to ease cough and congestion.
• Gargle with warm salt water for a sore throat (do not swallow).
• Take over-the-counter pain relievers like paracetamol or ibuprofen to reduce fever and aches. Always follow the instructions on the label.

Medical treatments

If you are at high risk of complications, a doctor may prescribe antiviral medications that can shorten the illness and reduce the risk of serious problems. These are not antibiotics and are only effective for the flu. They are most helpful when started within two days of symptoms beginning. For severe cases, hospitalization may be needed for supportive care such as oxygen or intravenous fluids.

When is surgery considered?

Flu does not require surgery. Surgery may be needed only if you develop a severe complication like a bacterial pneumonia that leads to an abscess, but that is very rare.

Living with this condition

During the flu, it is important to stay home, rest, and avoid contact with others until your fever has been gone for at least 24 hours without using fever-reducing medicine. Cover your mouth and nose when coughing or sneezing and wash hands often. Keep surfaces clean to prevent spreading the virus to family members.

Lifestyle tips

• Get plenty of sleep and avoid heavy physical activity until you feel fully recovered.
• Eat light, easy-to-digest foods if you have an appetite, but do not force yourself.
• Stay hydrated – sip water throughout the day.
• Avoid smoking and alcohol, as they can make symptoms worse.

Diet and exercise

There is no special diet for the flu, but balanced meals with fruits, vegetables, and protein can support recovery. Avoid strenuous exercise until you are completely well. Gentle stretching or short walks once your energy returns can help rebuild strength.

Mental health and emotional wellbeing

Having the flu can feel isolating and frustrating, especially if symptoms last a week or more. It is normal to feel low, anxious, or bored. Talk to friends or family through phone or video calls. If feelings of sadness or worry continue after you recover, speak to your healthcare provider. If you are having thoughts of harming yourself, reach out to a crisis line in your country immediately.

Prevention

Yes, you can reduce your risk of getting the flu. The most effective way is to get the annual flu vaccine. Good hygiene habits also help.

Vaccines

The flu vaccine is updated each year to protect against the most common flu viruses. It is offered free in many countries to people who are at higher risk or who want protection. The vaccine does not give you the flu and is safe. Even if you get the flu after vaccination, it is usually milder.

Screening programmes

There is no routine screening for the flu. Testing is done when a doctor suspects flu and needs the information for treatment or public health monitoring.

Complications

If left untreated

• Pneumonia – infection in the lungs that can be serious, especially for older adults or those with chronic conditions.
• Bronchitis – inflammation of the main airways, causing a lingering cough.
• Sinus or ear infections.
• Worsening of existing medical conditions like asthma, heart failure, or diabetes.

Long-term outlook

Most people recover from the flu within a week to 10 days without lasting problems. Even if complications occur, they are usually treatable with prompt care. The outlook is very good with rest and appropriate medical attention when needed. The flu vaccine and good hygiene offer strong protection.

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