Pneumonia: causes, symptoms, tests and treatment, a review

Pneumonia is a lung infection that ranges from mild to severe. Most people recover, but babies, older adults and people with other health problems can become seriously ill. This article explains the causes, symptoms, tests and treatment of pneumonia, using information from the NHS, MedlinePlus and the World Health Organization (WHO).

1. Introduction

Pneumonia is an inflammation (swelling and irritation) of the lungs, usually caused by an infection ^[1]. In pneumonia the tiny air sacs in the lungs, called alveoli, can fill with fluid or pus, which makes breathing painful and limits how much oxygen you take in ^{[2, 3]}. It can affect one or both lungs. How serious it is depends on the cause, the person's age and their general health ^[2].

WHO describes pneumonia as the largest infectious cause of death in children worldwide. It killed about 740,000 children under 5 in 2019, with deaths highest in southern Asia and sub-Saharan Africa. It can be prevented with simple measures and treated with low-cost medicines and care ^[3].

2. Causes and risk factors

Most cases are caused by bacteria or viruses ^{[1, 2]}. The main types are:

• Bacterial pneumonia, the most common type, which can happen on its own or after a cold or flu ^[2].
• Viral pneumonia, caused by germs such as the respiratory syncytial virus (RSV), flu viruses and the virus that causes COVID-19. It is often mild, but it can raise the risk of a second infection with bacteria ^[2].
• Fungal pneumonia, which is more common in people with long-term illness or a weak immune system ^[2].
• Aspiration pneumonia, which happens when food or fluid gets into the lungs ^{[1, 2]}.

Anyone can get pneumonia, but some people have a higher risk ^{[1, 2]}:

• Adults over 65, and babies and young children
• People with heart disease or a long-term lung condition, and those with diabetes, kidney disease, liver disease or sickle cell disease
• People who smoke, drink a lot of alcohol or are undernourished
• People with a weak immune system, or with trouble coughing or swallowing, for example after a stroke
• People who recently had a cold or flu, or who are in hospital, especially in intensive care

WHO adds that children are at higher risk if they are undernourished, have measles or HIV, live in crowded homes, are exposed to parental smoking, or breathe smoke from cooking or heating with wood or dung ^[3].

3. Signs and symptoms

Symptoms can appear suddenly or build up over several days ^[1]. Common signs include ^{[1, 2]}:

• Cough, sometimes bringing up phlegm
• Fever and chills
• Shortness of breath or fast breathing
• Chest pain when breathing or coughing
• Tiredness, body aches and loss of appetite
• Feeling or being sick, and sometimes diarrhoea

Symptoms can look different in some groups. Babies may have no clear signs, or may be restless, listless, vomit or make grunting sounds. Older adults may have milder symptoms, or may become weak or suddenly confused ^{[1, 2]}. WHO says doctors diagnose pneumonia in children under 5 who have a cough or difficulty breathing when they breathe fast or when the lower chest wall pulls in as they breathe in. Very sick infants may be unable to feed or drink ^[3].

4. Diagnosis and tests

Pneumonia can be hard to tell apart from a cold or flu, so diagnosis can take time. A doctor takes a history, examines you and listens to your lungs ^[2]. A chest X-ray and blood tests are common ^{[1, 2]}. In hospital, or for older adults and people with other illnesses, doctors may also check mucus coughed up from the lungs, do a CT scan, measure the oxygen in your blood (pulse oximetry) or look inside the airways (bronchoscopy) ^[2].

5. Treatment and recovery

Treatment depends on the type of pneumonia, the germ and how severe it is. Your doctor decides what is right for you ^[2].

• Bacterial pneumonia is treated with antibiotics, which do not work against viruses. The NHS says to take the full course even if you feel better sooner, and to contact your doctor if you are not improving after 2 to 3 days ^{[1, 2]}.
• Viral and fungal pneumonia may need antivirals or antifungals in some cases ^[2].
• Hospital care may be needed for severe illness. It can include oxygen if blood oxygen is low ^{[1, 2]}.
• Comfort measures. The NHS advises rest, plenty of fluids and staying home while feverish. It notes that coughing helps the body get rid of the infection, and it suggests checking with a pharmacist or doctor before using any pain, fever or cough medicine ^[1].

Recovery time varies. The NHS says most people improve in 2 to 4 weeks, depending on severity, while MedlinePlus notes that some need a month or longer ^{[1, 2]}. For children, WHO says most cases can be treated with oral antibiotics at a health centre, with hospital care kept for severe cases ^[3].

6. Prevention and self-care

Vaccines can help protect against infections that lead to pneumonia. The NHS lists the pneumococcal vaccine, the flu vaccine, the RSV vaccine for some groups and a seasonal COVID-19 vaccine for people at higher risk ^[1]. Ask your doctor which are advised for you or your child. WHO names vaccination against Hib, pneumococcus, measles and whooping cough as the most effective way to protect children, along with exclusive breastfeeding for the first six months, good hygiene and cleaner cooking fuels ^[3].

Other steps that help ^{[1, 2]}:

• Wash your hands often and cover coughs and sneezes.
• Do not smoke, because stopping smoking lowers the chance of getting pneumonia.
• Keep a healthy lifestyle, which may also help prevent pneumonia ^[2].

7. Special groups

Babies and young children, adults over 65 and people with long-term illness or weak immunity are at risk of becoming seriously ill, so they should get medical advice early ^{[1, 2]}. MedlinePlus lists possible complications such as bacteria spreading into the bloodstream, pockets of pus in the lung, problems with the covering of the lungs, kidney failure and breathing failure ^[2]. Older adults who become weak or suddenly confused, and infants who have fever, vomiting, low energy or restlessness, may have pneumonia and should see a doctor ^{[1, 2]}.

8. When to see a doctor

The NHS advises asking for an urgent doctor appointment if you have had a cough for up to 3 weeks, are coughing up yellow or green phlegm, have chest pain that comes and goes or happens when breathing or coughing, or feel short of breath ^[1]. Seek emergency help if you struggle to breathe or cannot speak, if your skin, lips or tongue look pale, blue or blotchy, if you cough up blood, if you suddenly become confused, or if a baby cannot be woken or feels floppy. Do not drive yourself, and bring your medicines with you ^[1].

In an emergency, call your local emergency number (112 in India, 911 in the United States).

9. Conclusion

Pneumonia is a lung infection that most often comes from bacteria or viruses. Most people recover with rest and the treatment their doctor advises, but young children, older adults and people with other illnesses can become very unwell. Vaccines, good hygiene and not smoking can lower the risk, and getting medical advice early matters for those at higher risk.