A fever may make you feel unwell, but it’s an important part of your body’s defence against infection. The rise in temperature helps your immune system to fight a bacteria or a virus more effectively.
So, what are the possible causes of fever in adults? And when is it necessary to take time off work when you have a fever?
What is considered a fever?
A temperature over 100.4°F or 38°C is considered a fever.
But there are many non-infectious conditions which can cause a fever, such as inflammatory diseases like arthritis. Certain medications are also known to cause fever.
Are fevers contagious?
It depends on the cause of the fever. Generally, if your fever is due to an infection that can be spread from one person to another, you will be contagious. But not all infectious diseases are contagious.
Fever caused by a non-infectious condition or medication is not contagious.
Should I go to work with a fever?
If your fever is caused by an infection you may be contagious. How long you are contagious for will depend on the type of infection.
The flu, for example, is most easily spread from the first day you start experiencing symptoms and for about three to seven days afterwards.
Gastroenteritis is a very contagious illness which can cause fever, vomiting and diarrhoea. It is recommended that you stay home until you have been symptom-free for at least 48 hours to avoid the spread of infection.
It is also common for some infections to make you contagious before you even start to feel ill.
The risk of spreading the illness is higher if you work closely with others. To help stop the spread of infection, avoid unnecessary contact with people until you are no longer contagious.
In the case of flu, the Centers for Disease Control and Prevention (CDC) recommends you stay at home until you have not had a fever for at least 24 hours (except to get medical care or other necessities.)
This is particularly important if you work with individuals who are more likely to develop complications from the flu. They include older adults, infants, and people with weakened immune systems.
In addition to being contagious, you might find it difficult to work productively when you are ill. In this case, it is worth staying at home until you feel better.
If you are ever in doubt about staying at home, check your work’s sick leave policy.
How to get rid of a fever
Most fevers will usually improve on their own within a few days, but there are steps you can take to ease any discomfort, including:
- keeping the room a cool, comfortable temperature
- wearing loose comfortable clothing and not overdressing
- drinking plenty of fluids to avoid dehydration
- not drinking alcohol (as it can make you more dehydrated)
- taking non-prescription painkillers to help lower the fever, such as paracetamol
When to worry
You should seek medical attention if you:
- have a temperature above 40°C or below 35°C
- have had a fever for more than five days
- have developed a rash that does not disappear when you press a glass on it (non-blanching rash)
- experience severe thirst
- urinate (pee) less than usual
- pass unusually dark urine
- feel light-headed or weak
- have sudden, severe muscle cramps
- have developed a fever after travelling abroad
Speak to your doctor if you have a fever and you have new or worsening symptoms such as a rash, stiff neck, shortness of breath, heart palpitations or chest pains.
You should seek immediate medical attention if you develop a fever and suffer from certain underlying health conditions like chronic lung disease, heart disease or diabetes. If you suffer from an underlying condition and are worried about a fever, see your doctor for advice.
Likewise, seek immediate medical help if you have a fever and a weakened immune system - for example, due to immunosuppressant medications like methotrexate or regular steroids, treatment for cancer, or if you are HIV positive.
A fever is often a sign that your body is fighting an infection. While this is a beneficial response, it may mean that you are contagious. If you’re worried about spreading an infection like the flu, you may want to avoid unnecessary contact with other people while you're infectious.
Some illnesses that cause fever may leave you feeling exhausted and make it difficult to function at work. If this is true for you, stay in bed and get plenty of rest until you feel better.
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