Viral vs bacterial – what’s the difference?

Viral vs bacterial – what’s the difference?

With winter upon us, many people will inevitably pick up sniffles, sore throats and colds, and get infections. But what’s the difference between a viral infection and a bacterial infection and how can both be treated?

Dr Lorraine Doherty, Assistant Director of Public Health (Health Protection) at the Public Health Agency, explains: “As the names suggest, viral infections are caused by viruses, bacterial infections by bacteria. Antibiotics are effective only against bacterial infections – they cannot help you recover from infections caused by viruses.

Viral infections

“A course of antibiotics won’t sort out your cold or flu. Cold and flu are viruses and antibiotics are useless against them. The best treatment is plenty of rest, hot drinks and maybe paracetamol to relieve aches and pains and help reduce a high temperature. Make sure not to take more than the stated dosage.

“Viral infections are very common and as well as cold and flus they can include many infections of the nose, sinuses, ears, throat and chest. Most of these can be self-treated without the need for a visit to the doctor and definitely no need for an antibiotic.

“In fact if you take antibiotics when you don’t need them, you could have some unpleasant side effects like an upset stomach, diarrhoea or a skin rash.

“Don’t forget, if you do have a cough or cold, it’s important to reduce your chances of spreading it to others by following good hygiene practices. Wash your hands regularly and if you do sneeze or cough, use a tissue to help stop the spread.” Antibiotics do not prevent viruses such as the common cold or flu from spreading to other persons

The first place to go if you’re feeling unwell is the pharmacist, who can usually provide over-the-counter medication to help deal with your symptoms until your illness passes.

If you must go to the doctor, don’t demand antibiotics from them.

Dr Doherty continues: “Take your doctor’s advice. They’ll know what the best action to take is and if they say you don’t need an antibiotic, don’t demand one. Taking antibiotics when you don’t need them can have unpleasant side effects.”

Bacterial infections

If you have a bacterial infection, your own immune system can clear many of these infections without the need for antibiotics. Antibiotics do little to speed up your recovery from most common infections. If your symptoms persist or if you have any concern, it is important that you see your doctor. If you really have a severe infection such as bacterial pneumonia, your doctor will prescribe antibiotics. 

“Antibiotics should only be taken for serious bacterial infections,” Dr Doherty says. “They are life-saving drugs for infections like pneumonia and meningitis. If we continue to take antibiotics when we don’t need to, bacteria build up resistance, making antibiotics useless against fighting them. As it is the bacteria and not the person that become resistant to the drugs, antibiotic resistance affects everyone.

“Infections caused by antibiotic-resistant bacteria can be difficult to treat so we need to protect the antibiotics we have to make sure they work when they’re needed most. We all have a role to play in using antibiotics wisely.”

Find out more information on viral and bacterial infections and antibiotics at


Notes to editor:

  • For information on staying well this winter, visit
  • When to contact the doctor – Contact your doctor if your symptoms start to change or get worse, or if you do not start to improve after a few days.