Viral fevers explained

18th March, 2021 • 5 min read

If you check your temperature and it’s higher than normal, you might have a fever – and viruses are a common cause.

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Read on to learn more about viral fever symptoms, diagnosis and treatment, plus when you should see a doctor.

What is a viral fever?

A ‘normal’ body temperature varies from person to person and also changes throughout the day. But a high temperature, or fever, is generally thought of as a body temperature of 38C or more.

Several health conditions can cause a fever but it’s usually a sign that your body is fighting off infection by ‘microorganisms’, such as bacteria or viruses. A viral fever is a high temperature that’s caused by a virus.

What causes a viral fever?

Common viruses that cause fever include cold and flu viruses and viruses that infect your tummy and gut.

But any type of viral infection can cause a fever. This is because many viruses are sensitive to changes in temperature, so fever is one of your body’s ways of fighting the infection.

You can become infected by a virus in different ways. Cold and flu viruses, for example, can spread if you breathe in droplets from the cough or sneeze of an infected person. With tummy bugs such as

, on the other hand, you get ill from eating food that has the virus in it. And some other viruses can be spread through insect bites.

Some viruses can cause fever and serious illness, which can lead to external and internal bleeding. This is called viral haemorrhagic fever. Viruses that can cause haemorrhagic fever include Ebola, dengue virus, hantavirus and the yellow fever virus.

What are the common viral fever symptoms?

Signs of a fever include:

  • a temperature of 38C or higher
  • a hot chest and back
  • warm, red skin
  • sweating
  • shivering (chills)

You might also have other symptoms, but these will mainly be due to whatever’s causing the fever, rather than the fever itself. They can include:

  • aches and pains
  • headache
  • tiredness and weakness

When to see a doctor

There are certain warning signs to watch out for when you have a fever. If you notice any of the following, you should see a doctor straight away:

  • confusion
  • severe headache
  • stiff neck
  • small, flat purplish red spots on your skin
  • low blood pressure
  • fast heart rate and/or breathing
  • shortness of breath
  • a temperature of more than 40C

You should also get medical advice if:

  • you’re travelling in or have recently been to an area where a serious infectious disease is common
  • you’re taking drugs that affect your immune system
  • your fever lasts for more than 24 to 48 hours

How is a viral fever diagnosed?

If you have a fever, it’s likely that it’s caused by either a viral or bacterial infection. Your doctor may want to check if bacteria or a virus made you ill by looking at your medical history and doing a physical examination and sometimes simple tests, such as a urine test.

If it isn’t a bacterial infection, it’s often difficult to know exactly what virus has caused a fever. But the good news is that viral fevers usually go away without treatment. Unless your symptoms are severe, you probably won’t need further tests.

However, other tests may be needed if you live or work around certain animals or insects that carry diseases, or if you’ve recently been in areas where a particular virus is common.

What viral fever medicines and treatments are available?

A viral fever can usually be managed at home with self-care treatments to reduce symptoms, such as:

  • resting as much as possible
  • drinking plenty of fluids to avoid dehydration
  • taking medication that reduces fever and pain, such common painkillers – ask your doctor or pharmacist about how to use these medicines safely

Please note that this advice is for adults only and doesn’t apply to children.

Should I get antibiotics for viral fever?

No – antibiotics can’t be used to treat viral infections.

Antibiotics are designed to fight bacteria, which are completely different organisms, so they won’t do anything to make you feel better if you have a viral fever. The only time you should take antibiotics with a viral infection is if your doctor thinks you also have a bacterial infection.

If you take antibiotics when you don’t need to, they may not work as effectively when they’re really needed.

Key points

  • if you have a body temperature of 38C or more, you probably have a fever
  • viruses and bacteria are common causes of fever
  • a viral fever usually goes away on its own and doesn’t need specific testing or treatment
  • certain other symptoms with a fever can suggest a more serious condition that needs treatment

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.