What are the most common infectious illnesses?

What the most common infectious illnesses are, symptoms, how you can help and when to call your GP.

Colds, coughs and congestion

Babies and children can normally catch several colds each year. Catching them can be a miserable time for them as well as for you.

Colds are infections of the nose, throat and sinus caused by one of many different viruses. They are most commonly spread through droplets produced when someone coughs or sneezes, and can be easily spread through hand-to-hand contact.

What are the symptoms?

The main symptoms of a cold will develop gradually and can include:

  • A runny or blocked nose
  • A cough
  • Sneezes
  • Red eyes
  • Possibly a mild fever (a temperature higher than 37.5C)
  • Loss of appetite
  • Being generally unsettled
  • These symptoms can last a few days, a week, or possibly longer with very young babies.

How you can help

Colds are caused by a virus and viruses cannot be treated with antibiotics. These medicines will only be prescribed by your GP if they suspect a bacterial infection, for example, in the chest. This is because antibiotics only act on bacteria, and will not have any effect on a cold caused by a virus. Cough and cold medicines should not be taken by children under the age of six. It is generally thought by professionals that most of the treatments you can buy in the shops are ineffective.

There are other ways to help with the symptoms of a cold. It is important to make sure your baby drinks enough fluids. Offer your baby plenty of breast milk or formula, and, if your baby is over four months, you can offer water. If your baby is not passing as much urine as usual, has sunken eyes or a sunken soft spot at the top of the head, this could be a sign of dehydration and you should see your GP.

You may be worried that your baby should be wrapped up more when they have a fever. This isn’t the case. NEVER use pillows, loose towels or blankets in your baby’s cot, as these can be potential suffocation risks and are linked to an increased risk of Sudden Infant Death Syndrome (SIDS). This risk can also be increased if the baby is too hot. Make sure you regularly check the temperature of the room and feel your baby for signs of being too warm. For more information on safer sleep for your baby, visit The Lullaby Trust.

Watching your baby fight a cold for the first time may be distressing for you and them. In time you will learn how your baby likes to be comforted, and this will help you to treat your child with confidence.

To help avoid infection, you can follow the steps at the beginning of this information.

When to call your GP

Most colds can be managed at home. However, if your baby’s symptoms do not improve, or they worsen, you should contact your GP. If your baby is dehydrated, or has difficulty breathing you should contact your GP immediately.


Bronchiolitis is the swelling of the small airways in the lungs, caused by infection. This leads to a build-up of mucus, causing breathing difficulties. It is a common illness that affects babies and young children. It is often caused by a cold virus or an infection called Respiratory syncytial virus (RSV).

Many adults, children and babies catch RSV and have very similar symptoms to that of a cold. In fact, in most cases you would not know whether your illness was caused by this virus, or many of the other viruses which cause similar symptoms.

For more information about bronchiolitis, visit this page.


Pneumonia is an infection of the lungs causing the tissue to swell and the air sacks to fill with fluid, making it harder to take in oxygen. It can take hold after a cold, flu or other illness, and can be caused by bacteria, viruses or fungi.

What are the symptoms?

Signs of the infection can appear over a day or two, or can develop more slowly. The symptoms can include:

  • A fever
  • A cough
  • Rapid breathing
  • Breathing difficulties
  • Pain or discomfort in the chest
  • Your baby could also show signs of feeling generally unwell, like not feeding as usual.

How you can help

You should see your GP if you think your child has pneumonia. Some cases can be treated at home with antibiotics if the GP believes bacteria has caused the infection. But high risk babies might need a short stay in hospital to help with their breathing. The Hib vaccine included in the 5-in-1 injection, and the pneumococcal (PCV) vaccine, are both given to babies at eight weeks. These injections can protect against some types of pneumonia.

When to call your GP

Call your GP if your baby shows any of the symptoms listed above, or appears to be sleepier than usual. If your baby has any trouble with breathing, you should contact your GP immediately.

Influenza (flu)

Influenza, or flu, is a viral infection of the lungs and upper airways. It is caused by several different viruses. Those at risk of becoming more seriously ill from a flu infection are the very young, over 65s, or those with long-term health problems such as asthma or diabetes. Flu viruses spread like cold viruses, through droplets produced when you cough or sneeze and hand-to-hand contact.

What are the symptoms?

Symptoms are very similar to a cold but with the addition of:

  • A sudden fever
  • Possibly a dry cough.

Fever may be the first sign of the illness. Other symptoms include:

  • Tiredness
  • Aching muscles
  • Sneezes
  • Runny nose
  • Diarrhoea or vomiting
  • Loss of appetite.

The worst of the symptoms tend to last a few days and the cough and weakness can last up to two weeks.

How you can help

Plenty of rest and extra fluids are essential. Liquid paracetamol for children can be given to relieve symptoms in the meantime.

If your baby is at home, is more than six months old, and has been diagnosed with Chronic Lung Disease (CLD), your GP or health centre may contact you during the winter months (October to March). They may offer your child (and sometimes you) the flu vaccine to protect against complications brought on by the flu. This is because your baby will be more at risk if they have been diagnosed with CLD. It’s common to get the flu more than once, so it is best to avoid crowded places during the winter months and to wash your hands often and thoroughly. See the section on reducing the risk of infection for more tips on protecting your baby.

When to call your GP

If you think your baby might have flu, a fever, or you are concerned at all, you should call your GP.

Diarrhoea and vomiting

Norovirus and Rotavirus (as well as some other stomach bugs) are very common. Hundreds of thousands of people every year catch these infections. You may have heard Norovirus described as the ‘winter vomiting bug’ because the illness is more common in winter. However, any of these viruses can be caught at any time of the year. They are highly contagious, meaning they can spread to other members of your family quickly.

What are the symptoms?

Norovirus, Rotavirus and other stomach bugs cause vomiting and diarrhoea. This can come on very suddenly. Other symptoms include a fever, headaches and painful stomach cramps.

How you can help

There is no specific cure for these viruses, so you have to let the illness run its course. It should not last more than a couple of days. You can usually care for your baby at home, making sure that they keep taking in plenty of fluids.

Very young babies, especially those at higher risk, are more likely to become very poorly from stomach infections. If you are at all worried, you should always visit your GP. Extra care should be taken to prevent babies and small children who are vomiting or have diarrhoea from dehydrating.

If your baby is eating solid foods and they feel like eating, try to give them foods that are easy to digest.

Following our tips on preventing infection will help to protect your baby. These viruses are particularly infectious, so if you or anyone else in the family becomes ill, follow our tips for reducing the risk of infection to help avoid it spreading. If anyone else is planning on coming into contact with your baby and they have been sick or had diarrhoea recently, ask them to not visit until they are fully recovered.

A Rotavirus vaccine is offered to babies at eight and 12 weeks, along with their other vaccines. See our Vaccinations section for more information.

When to call your GP

Contact your GP for advice if your baby’s symptoms last longer than a few days, if they have a serious illness that might be made worse by their symptoms, or if you are struggling to keep your baby hydrated. If the symptoms are particularly bad, or you are at all worried, you should always seek help.