How to tell the difference between a cold and flu

You wake up with a sore throat and a cough.  Your nose is blocked, and you feel exhausted.  While you deliberate whether or not to ring in sick, you wonder: is this just a cold, or could it be flu (influenza)?  Here’s a simple way to identify an illness that’s more likely to be flu (and why it’s important to know the difference).

How to distinguish a cold from flu using the acronym “FACTS”

F stands for Fever

If your temperature is higher than normal (38.0 C or above), it's more likely that you've got flu.  Colds, although they can make you feel miserable, are unlikely to trigger a fever. 

A stands for Aches

Feel achy all over?  That’s another clue that suggests flu, as colds are unlikely to cause body aches. 

C stands for Chills

Feeling unable to warm up, no matter how many layers of blankets, is more suggestive of flu than a cold.

T stands for Tiredness

While a bad cold and flu can both make you feel less energised than usual, the flu is likely to make you so tired it’s difficult to get out of bed.  If you’re still able to go about your normal routine, it’s more likely that you’ve got a cold.

S stands for Sudden Onset

If you feel like all of a sudden you've been hit by a ton of bricks (think hours rather than days), it’s more likely you have flu than a cold.  Even the worst colds tend to start with mild symptoms and take several days before you feel really under the weather.

Other symptoms

For the elderly and young children, other symptoms of flu can include nausea, vomiting, and diarrhoea.  (Note that this isn’t usually true for people of other ages—for everyone else, these symptoms would be more suggestive of gastroenteritis than flu.)  

If you think you may have flu

Most healthy people with flu feel much better after about a week, as their immune system works to fight the infection.  Things you can do at home include getting plenty of rest and drinking lots of fluid.  For some individuals, however, flu can be much more serious and can cause dangerous complications that can be life threatening (indeed, 600 individuals in the UK die of flu each year, rising to 13,000 in an epidemic).  People at a higher risk of a flu complication include adults aged over 65, pregnant women, babies and very young children, individuals with a long-term medical condition such as diabetes, heart disease, lung disease, kidney disease, or a neurological disease, and individuals with a weakened immune system (such as those on chemotherapy or those with certain illnesses).  For these individuals, it makes good sense to contact a clinician as soon as possible if you suspect flu.

How is flu treated?

If you think you have flu, you may benefit from taking an antiviral medication such as Tamiflu.  When taken early (ideally within 48 hours of feeling unwell), antiviral medications can shorten the duration of flu, make the symptoms you do experience less severe, and make a complication from flu less likely.  If you’re in a higher risk group, antiviral medication may be available on the NHS.  If you’re not in a higher risk group, antiviral medication is not generally available on the NHS but can be prescribed privately.  Because flu is caused by a virus (and not a bacteria), antibiotics are of no use in treating flu.

Prevention

The most effective way to prevent flu is by immunisation every year with a flu injection.  It is not always possible to avoid flu by simply avoiding those who are unwell, since flu is infectious for about 24 hours before any symptoms start.  Despite popular belief, the flu immunisation cannot give you flu, since it doesn’t contain any live viruses.  (If you're in a higher risk group, the injection may be available on the NHS; anyone else can have an immunisation privately.)  Other important ways to avoid flu include good hand hygiene (that means washing hands with soap and water, and using alcohol hand gels regularly),  and disinfecting surfaces that are touched frequently, such as computer keyboards, telephones, and door handles.  If you have flu, you can avoid infecting others by staying away from work until you’re feeling better, and using tissues to cover your mouth when you cough and sneeze.

The bottom line

Flu is unpleasant for nearly everyone who gets it, and can be dangerous for some.  Prevention is better than cure, but if you do find yourself feeling unwell, take rest, drink fluids, and remember that antiviral medication is an option to help get you back on your feet faster.