Chest infection, adult

Page last reviewed: 13/07/2011

A chest infection is a bacterial or viral infection of the airways leading down into the lungs, or of the lungs themselves.

The main symptoms of a chest infection include:

  • a chesty cough that can often bring up phlegm (thick mucus)
  • breathing difficulties
  • chest pain

Chest infections can range from being mild to life threatening.

Types of chest infection

There are two main types of chest infection:

  • acute bronchitis, which is the more common and less serious type of infection
  • pneumonia, which is less common than acute bronchitis but more serious

Acute bronchitis

Acute bronchitis is a short-term infection of the lining of the air tubes of the lungs, which are known as the bronchi.

The infection is usually caused by a virus, and often follows a cold or influenza (flu). Smoking increases your chances of developing the infection. Most people do not require medical treatment because the infection usually passes within seven to ten days.


Pneumonia is an infection that causes the tiny air sacs in your lungs, known as alveoli, to become inflamed and filled with fluid. Pneumonia is usually caused by bacteria, although some cases can be caused by viruses. 

People with mild pneumonia can usually be treated at home. However, if you have severe pneumonia, you may need to receive treatment in hospital. People who are very young or very old, and those with another serious health condition, are more likely to require hospital treatment if they develop pneumonia.

How common are chest infections?

Chest infections are very common and account for around one in five GP visits.

Acute bronchitis is the most common type of chest infection, affecting about 4.5% of the population each year. The condition is most common during autumn and winter.

Pneumonia is less common, affecting just over 1% of people each year.

People who are over 65 years of age are most at risk of developing pneumonia, and the rates of pneumonia are four times higher in this age group compared with other age groups. As with acute bronchitis, pneumonia is most common during the autumn and winter months.

Chest infections are contagious

Although acute bronchitis and pneumonia are not as contagious as conditions such as flu, they can be passed on to others through coughing and sneezing.

It is therefore important to cover your mouth when you cough or sneeze, and to wash your hands regularly. Throw away used tissues immediately.


The outlook for acute bronchitis is very good. The condition is usually mild and self-limiting, which means that it gets better by itself without the need for medical treatment. The symptoms should pass within seven to ten days.

The outlook for pneumonia can vary widely, depending on a number of other factors that make the person more vulnerable to the effects of infection. These include:

  • being over 65
  • having a weakened immune system (the body's natural defence against infection)
  • having another serious health condition, such as chronic obstructive pulmonary disease (COPD), which is a general term describing a number of lung conditions that cause moderate to serious breathing difficulties

Depending on these risk factors, the likelihood of dying as a result of pneumonia can range from less than 1% to 50%.

Acute bronchitis does not usually require medical treatment.

Pneumonia can usually be treated with antibiotics. In mild cases, tablets (oral antibiotics) are usually recommended, with injections (intravenous antibiotics) being used in more serious cases.  


There are two vaccines that can help provide protection against many of the strains of bacteria that are known to cause pneumonia. These are:

  • pneumococcal conjugate vaccine (PCV), which is given to all children under two years of age as part of the childhood vaccination programme
  • pneumococcal polysaccharide vaccine (PPV), which is recommended for people who are 65 years of age or over, and those who have a high risk of developing complications from pneumonia, due to a serious health condition

In addition, seasonal influenza vaccine is strongly recommeneded for those who are 65 years or over and those with chronic illness as serious respiratory complications can develop, including pneumonia and bronchitis, to which older people and those with certain chronic medical conditions are particularly susceptible.

Page last reviewed: 13/07/2011

Acute bronchitis

Acute bronchitis is usually a mild, self-limiting illness (an illness that resolves itself without the need for medical treatment). Symptoms of acute bronchitis include:

  • a persistent chesty cough
  • coughing up yellow or green phlegm (thick mucus)
  • breathlessness on exertion (above the usual level)
  • wheeziness
  • dry mouth
  • high temperature (fever) of 38C (100.4F) or above (although in some people, such as the elderly, the temperature may fall)
  • headache
  • loss of appetite

The cough usually lasts seven to ten days, although it can persist for up to three weeks.

Acute bronchitis often causes headaches and a sense of feeling generally unwell. As well as being caused by the infection, these symptoms can also sometimes be caused by dehydration. It is therefore very important to drink plenty of fluid.


Common symptoms of pneumonia include:

  • difficulty breathing (breaths are rapid and shallow)
  • a cough that brings up phlegm (thick mucus)
  • rapid heartbeat (tachycardia)
  • high temperature (fever) of 38C (100.4F) or above
  • chest pain

Less common symptoms of pneumonia include:

  • coughing up blood
  • headaches
  • loss of appetite
  • fatigue
  • nausea
  • vomiting
  • joint and muscle pain
  • a blue tinge to the skin (cyanosis)

Sometimes, elderly people with pneumonia may become confused and disorientated.

When to seek medical advice

See your GP if:

  • you have a high temperature (this is usually a sign of a more serious type of infection)
  • you feel so unwell that you are unable to manage and cope with your normal daily activities
  • you feel confused and disorientated
  • you experience symptoms of breathlessness when you are at rest, or you become more breathless than you would expect during physical activity
  • you have a sharp pain in your chest
  • you cough up blood-stained phlegm (thick mucus)
  • your symptoms last longer than three weeks
  • you have a weakened immune system due to another condition, such as HIV, or as the result of treatment, such as chemotherapy

Also contact your GP if you have a chronic (long-term) health condition that could make you more vulnerable to the effects of a chest infection such as:

  • heart disease, where the blood supply to the heart is reduced
  • diabetes, where the body does not produce enough insulin or cannot make use of insulin in the right way
  • kidney disease, where the kidneys lose some of their ability to filter toxins out of the blood
  • asthma, where a number of substances, such as dust mites or pollen, can cause the lungs to become inflamed, leading to breathing difficulties
  • chronic obstructive pulmonary disease COPD), a general term for a group of lung conditions that cause serious breathing problems

Page last reviewed: 13/07/2011

To understand what causes a chest infection, it is useful to learn about how the lungs work.

The lungs

Your lungs are like two large sponges that are filled with tubes. As you breathe in, you take in oxygen through your nose and mouth. It then goes through a tube in your neck, called the windpipe or trachea.

The trachea splits into two tubes, one for each lung. These are called the primary bronchi. The bronchi divide into smaller and smaller bronchi which have tiny air sacs (alveoli) at the end. The oxygen is passed into your blood from the alveoli, before being pumped around your body by your heart.

As well as oxygen, bacteria and viruses in the air can also be passed down into your lungs. This usually does not cause problems because your immune system (the body's natural defence against infection) is able to kill the bacteria or viruses.

However, infection can occasionally take hold, particularly if your immune system has been weakened by other conditions, or your lungs have been irritated by cigarette smoke.

Acute bronchitis

Most cases of acute bronchitis are caused by viruses, although sometimes they are caused by bacteria.

Acute bronchitis is a temporary inflammation of the trachea and the major bronchi, caused by infection. The inflammation causes swelling of the airways and a build-up of phlegm (thick mucus), which is cleared from the airways by coughing (which can sometimes last for up to three weeks).


Pneumonia is an infection of the tissues of the lung. Germs that cause infections, such as pneumonia, are often passed around in the community. In some people, the germs cause pneumonia to develop.

In adults, the most common cause of pneumonia is a type of bacterium called Streptococcus pneumoniae. This form of pneumonia is sometimes called pneumococcal pneumonia.

Less commonly, other types of bacteria can cause pneumonia, including:

  • Haemophilus influenzae
  • Staphylococcus aureus

Viruses can also cause pneumonia, most commonly the respiratory syncytial virus (RSV). Other viral causes include:

  • varicella-zoster (the virus that causes chickenpox)
  • the flu (influenza) type A or B virus

Viral pneumonia tends to be more common in young children than in adults.

Some groups of people have a higher risk of developing pneumonia, such as:

  • babies and very young children
  • elderly people
  • people who smoke or are exposed to smoke in their environment
  • people with other health conditions
  • people with a weakened immune system (the body's natural defence against infection)

Other health conditions that increase the risk of pneumonia developing can include:

  • another lung condition, such as asthma or cystic fibrosis
  • a heart condition
  • a kidney or liver condition
  • a lowered immune system

Your immune system can be lowered as a result of:

  • a recent illness, such as flu
  • treatment for cancer, such as chemotherapy
  • taking medicines or treatment that suppress the immune system
  • a health condition, such as HIV or AIDS

Page last reviewed: 13/07/2011

Acute bronchitis

A medical diagnosis of acute bronchitis is not usually required unless your symptoms are particularly severe or last longer than three weeks.

If you see your GP, they will usually be able to make a diagnosis by asking about your symptoms and listening to your chest using a stethoscope (a piece of medical equipment that is used to listen to the heart and lungs).

Ruling out other conditions

In confirming a diagnosis of acute bronchitis, your GP may need to rule out other lung infections, such as pneumonia, which has similar symptoms to bronchitis.

If your GP thinks that you may have pneumonia, you may need to have a chest X-ray. They may also take a sample of mucus for testing.

If an undiagnosed underlying condition is suspected, such as asthma or emphysema (damage to the small airways in your lungs), your GP may suggest that you have a pulmonary function test.

If you have a pulmonary function test, you will be asked to take a deep breath before blowing into a device called a spirometer, which measures the volume of air in your lungs. A decreased lung capacity may indicate that you have an underlying health problem.


To help make a diagnosis, your GP will ask you about your symptoms. For example, they may ask you:

  • whether you are breathing faster than usual (respiratory rate)
  • whether you feel breathless
  • how long you have had your cough
  • whether you are coughing up phlegm (thick mucus) and what colour it is
  • whether the pain in your chest is worse when you breathe in or out

Your GP will probably use a stethoscope to listen to the back and front of your chest to check for any crackling or rattling sounds. They may also tap your chest and listen to the sound that is produced. If your lungs are filled with fluid, they will produce a different sound compared with normal, healthy lungs.

Your blood pressure will also be checked because an unusually low blood pressure (hypotension) may be a sign that you have a more serious type of pneumonia.

Your GP may also carry out a test called a pulse oximetry test. A sensor is put on your fingertip, ear or toe. This measures how much oxygen is present in your blood. Unusually low levels of oxygen may be a sign that you have a more serious type of pneumonia.

Further testing

Further testing is usually only required if your chest infection symptoms are severe. A chest X-ray can highlight the extent to which pneumonia has affected your lungs. Other tests that your GP may suggest include:

  • sputum test, where you cough up some phlegm (mucus) into a container so that it can be tested in a laboratory
  • blood tests

The samples that are taken during sputum and blood tests will be analysed in a laboratory to help identify the germ that is causing your infection.

If the tests identify the germ, your GP may decide to adjust your treatment. Delaying treatment until the results of the test are known could be dangerous, so in most cases chest infections are initially treated with broad-spectrum antibiotics (antibiotics that are known to be effective against a wide range of bacteria). Once the exact germ that is causing your infection has been identified, your GP may adjust your treatment accordingly. 

Screening for lung cancer

Although uncommon, pneumonia can sometimes be a symptom of underlying lung cancer in people who smoke and are 50 years of age or over.

If you smoke, have pneumonia and are 50 or over, your GP may refer you for a chest X-ray. Lung cancer usually shows up on X-rays as a ‘white-grey’ mass.

Sometines a follow-up X-ray is recommended six weeks later. This is a way of ‘double-checking’ that all is well with your lungs.

Useful Links

Page last reviewed: 13/07/2011

Acute bronchitis

As most cases of acute bronchitis are mild and self limiting (they resolve themselves in seven to ten days), they do not usually require treatment, and the symptoms can be easily managed at home.

Managing symptoms at home

If you have acute bronchitis:

  • get plenty of rest
  • drink plenty of fluid to prevent dehydration and to thin the mucus in your lungs, making it easier to cough up
  • treat headaches, fever and aches and pains with paracetamol or ibuprofen (ibuprofen is not recommended if you have asthma)

There is little evidence that cough medicines work, and coughing enables you to clear the excess phlegm (mucus) from your lungs. Therefore, suppressing your cough may make the infection last longer. A warm drink of honey and lemon may help relieve the discomfort that is caused by coughing, although this is not suitable for people with diabetes.

Stop smoking

If you smoke, stop immediately. Smoking aggravates bronchitis and increases your risk of developing a chronic (long-term) condition. Giving up smoking while you have bronchitis can also be the perfect opportunity to quit altogether.


Although treatment from a GP for acute bronchitis is rarely necessary, there may be times when you should see your GP.

Your GP will not routinely prescribe antibiotic treatment for acute bronchitis for a number of important reasons:

  • Most cases of acute bronchitis are caused by viral infections, which means that antibiotics will have no effect.
  • You are almost as likely to experience a side effect from taking antibiotics, such as vomiting and diarrhoea, as you are to receive any benefit from the treatment.
  • The more antibiotics are used to treat mild conditions, the greater the likelihood that the bacteria will develop resistance to antibiotics and go on to cause more serious infections.

Many experts believe that the reason there are so many dangerous strains of antibiotic-resistant bacteria, such as MRSA and multi-drug resistance tuberculosis (MDR-TB), is because antibiotics have been overused in the past to treat mild conditions.

The use of antibiotics is usually only recommended if it is thought that you have an increased risk of developing a secondary lung infection, such as pneumonia, due to factors such as:

  • being over 75 years of age and having a high temperature (fever) of 38C (100.4F) or above
  • having long-term problems with your lungs or heart, such as chronic obstructive pulmonary disease (COPD) or heart failure
  • having a weakened immune system (immunocompromised) as a result of a condition, such as diabetes or cancer, or due to certain types of medical treatment, such as chemotherapy

If you are prescribed antibiotics for bronchitis, it is likely to be a five-day course of amoxicillin, oxytetracycline or doxycycline. Possible side effects of these medicines include:

  • nausea
  • vomiting
  • diarrhoea


If you have pneumonia, depending on how serious your condition is, you may be treated at home or at hospital. Your GP will make a detailed assessment based on how ill you are and the likelihood that you will become more seriously ill.

CRB-65 score

Most GPs use a scoring system that is known as the CRB-65 score to assess the potential seriousness of pneumonia. CRB-65 stands for:

  • Confusion. Signs of mental confusion may mean that you have a more serious infection.
  • Respiratory rate. Your respiratory rate is how many breaths you take in a minute (more than 30 breaths a minute may be a sign that your lungs are not working properly).
  • Blood pressure. Low blood pressure can be a sign of a more serious infection.
  • 65 refers to whether you are 65 years of age or over. Older people are more vulnerable to the effects of pneumonia

Each one of the above criteria has a score of one, which added together make up the total CRB-65 score.

  • A CRB-65 score of zero means that you have a low risk of developing complications and that you can usually be treated at home.
  • A CRB-65 score of between one and two means that you have a medium risk of developing complications and that you should have a same-day assessment by an expert in treating pneumonia. Depending on the results of the assessment, you may be able to be treated at home or you may need to be admitted to hospital.
  • A CRB-65 score of three or more means that you have a high risk of developing complications and you should be immediately admitted to hospital for treatment.

Treatment at home

If you are being treated at home, you will usually be prescribed a seven-day course of antibiotics, with amoxicillin being the preferred choice. If you are allergic to amoxicillin, alternative antibiotics, such as doxycycline, can be used.

The most common side effects of the antibiotics that are used to treat pneumonia are:

  • nausea
  • vomiting
  • diarrhoea

However, these side effects are usually mild.

Less commonly, doxycycline can make your skin more sensitive to the effects of sunlight. Therefore, minimise your exposure to direct sunlight and avoid using sun lamps and sunbeds if you are taking doxycycline.

If you are prescribed antibiotics, it is important to finish taking your course, even if you are feeling better. Stopping the course too soon could cause the pneumonia to return.

Self care

The steps listed below may help ease your pneumonia symptoms.

  • Painkillers, such as paracetamol or ibuprofen, will help relieve pain and reduce a high temperature.
  • As with acute bronchitis, cough medicines are not recommended for treating the symptoms of pneumonia. Coughing enables you to clear phlegm (thick mucus) from your lungs, so trying to stop your cough could make the infection last longer. A warm drink of honey and lemon may help relieve the discomfort that is caused by coughing.
  • Drink plenty of fluids to avoid becoming dehydrated.
  • Get plenty of rest to help your body recover.
  • If you smoke, stop. Smoking damages your lungs, so this is a good opportunity to stop smoking altogether.

Treatment at hospital

If your symptoms are moderate, you can usually be treated with antibiotic tablets (oral antibiotics).

If your symptoms are severe, treatment usually involves giving you antibiotics directly into your vein through a drip in your arm (intravenous antibiotics). You may also be given additional fluids to stop you becoming dehydrated and oxygen to help you breathe.

Depending on how well you respond to treatment, it may be possible to switch from intravenous to oral antibiotics after a few days.

Most people who are treated in hospital required a 7-10 day course of antibiotics. How long it will take before you are well enough to return home will depend on your general state of health and whether you experienced any complications.


It is usually recommended that you attend a follow-up examination six weeks after the onset of your symptoms to check that the pneumonia has not caused any serious or permanent damage to your lungs.

The follow-up examination usually involves taking a chest X-ray so the state of your lungs can be assessed.

Page last reviewed: 13/07/2011

Acute bronchitis

Sometimes, acute bronchitis can cause a secondary infection in your lungs. The lungs can be weakened by the original infection and become more vulnerable to secondary infection by bacteria.

If you develop a secondary infection, it can be more serious than acute bronchitis. It can usually be treated with antibiotics. Occasionally, acute bronchitis can lead to pneumonia, particularly if you have other health conditions.

See your GP if:

  • you develop symptoms of a high temperature (fever) of 38C (100.4F) or above, or your existing high temperature suddenly worsens
  • you become drowsy, confused or disorientated
  • you develop chest pains
  • your breathing suddenly becomes more rapid
  • you become short of breath
  • your cough lasts more than three weeks
  • you have recurring bouts of acute bronchitis
  • you cough up blood


Pleural effusion

Pleural effusion is a common complication of pneumonia that affects around 1 in 2 people who are admitted to hospital for moderate to severe pneumonia.

A pleural effusion is where an excess amount of fluid gathers inside the double-layered membrane (covering) that surrounds the lungs, and is known as the pleura.

The fluid can place pressure on the lungs, making breathing difficult. Pleural effusion will usually resolve itself when pneumonia is treated.

In cases of pleural effusion, it is usually recommended that a fluid sample is taken and checked to determine whether the fluid has become infected (see below). If no infection is present, a 'watch and wait' strategy is usually recommended because most cases of pleural effusion will be resolved once the underlying pneumonia infection has passed.


In around 10% of pneumonia cases that are treated in hospital, the fluids that make up a pleural effusion will become infected by bacteria. This is known as empyema. The bacteria can cause a build-up of pus, which can sometimes reach up to around a quarter of a pint (142.5mm)

Symptoms of empyema include:

  • chest pain, which is made worse when breathing in
  • dry cough
  • high temperature (fever) of 38C (100.4F) or above
  • chills
  • excessive sweating, particularly at night
  • shortness of breath
  • general sense of feeling unwell

Empyema is usually treated using a combination of antibiotics and a procedure that drains the pus out of the pleura. This is usually done by making a small incision (cut) in your chest (under a local anaesthetic), and then inserting a tube into the pleura to drain away the pus and fluid.

The most serious cases of empyema may require surgery to remove the pus and repair any underlying damage to your pleura and lungs.

Lung abscess

A lung abscess is a rare complication of pneumonia and is mostly seen in people who have a serious, pre-existing illness or those with a history of severe alcohol misuse.

A lung abscess is a pus-filled cavity that develops inside the tissue of the lungs. The symptoms of a lung abscess are the same as those of severe pneumonia. In addition, you may begin to cough up unpleasant-smelling phlegm (thick mucus) and experience swelling in your fingers and toes.

Most cases of lung abscesses can be treated using antibiotics. This usually involves an initial course of intravenous antibiotics (directly into a vein through a drip) followed by oral antibiotics (tablets) for four to six weeks.

Most people who have a lung abscess will experience an improvement in their symptoms within three to four days. It is important to finish your recommended course of antibiotics, even if you feel perfectly healthy, to prevent re-infection of your lungs.

Around 10% of people will require surgical treatment because they fail to respond to the antibiotics. Surgery usually involves draining the pus out of the abscess or removing the affected section of the lung.

Metastatic infection

Another rare and serious complication of pneumonia is metastatic infection. Metastatic infection means that the infection has spread from the lungs to another part of the body.

The first place that an infection usually spreads to is the blood, which is known as septicaemia.

Symptoms of septicaemia include:

  • high temperature (fever) of 38C (100.4F) or above
  • fast heartbeat (tachycardia)
  • fast breathing
  • low blood pressure (hypotension) which will cause you to feel dizzy when you stand up
  • a change in mental behaviour, such as confusion or disorientation
  • diarrhoea
  • reduced urine flow
  • cold, clammy skin
  • pale skin
  • loss of consciousness

Once your blood has become infected, it is possible for the infection to spread to other organs in your body, such as:

  • the outer layers of your brain (meningitis)
  • the lining of your abdomen (peritonitis)
  • the inner layer of your heart (endocarditis)
  • your joints (septic arthritis)

These types of metastatic infections are usually very serious and require aggressive treatment with high-dose intravenous antibiotics.

Page last reviewed: 13/07/2011


If you have had recurring episodes of acute bronchitis or one or more episodes of pneumonia, your GP may recommend that you have vaccinations for influenza (flu) and pneumococcal infections (a bacteria that can cause pneumonia, meningitis and infection of the blood).

The vaccination should help prevent you getting chest infections in the future. Vaccinations are usually recommended for:

  • people over 65 years of age
  • people with either chronic respiratory, heart, renal or liver conditions
  • people with diabetes
  • people with sickle-cell anaemia (an inherited blood disorder)
  • people with conditions that affect the immune system, such as HIV
  • children under five years of age


To reduce the risk of spreading bacteria to other people, cover your mouth when you cough or sneeze and wash your hands regularly. Throw away any used tissues immediately.

Quitting smoking

If you are a smoker, the best thing you can do to prevent developing a chest infection is to stop. Smoking damages your lungs and weakens their defences against infection.

You can also call the National Smokers Quitline at 1850 201 203, or log on to, or the HSE facebook page at


Excessive and prolonged alcohol misuse is known to weaken your lung's natural defences against infections (their immune response), making you more vulnerable to pneumonia

One study found that 45% of people who were admitted to hospital for pneumonia had an alcohol misuse problem. Alcohol misuse is defined as regularly drinking over the recommended weekly limits (21 units of alcohol for men and 14 units of alcohol for women).

Not only does alcohol misuse increase your risk of developing pneumonia, but it also increases your risk of it being more serious. It is estimated that people who misuse alcohol are three to seven times more likely to die from pneumonia than the general population.

If you drink alcohol, do not exceed the recommended daily limits (three to four units a day for men and two to three units a day for women).

Contact your GP if you are finding it difficult to moderate your drinking. Counselling services and medication are available to help you reduce your alcohol intake.


Eating a healthy diet is known to strengthen the immune system, making you less vulnerable to developing chest infections. A low-fat, high-fibre diet is recommended, including whole grains and plenty of fresh fruit and vegetables (at least five portions a day).

Content provided by NHS Choices and adapted for Ireland by the Health A-Z.

Browse Health A-Z