Pneumonia: Symptoms, Causes, and When to Seek Care

Pneumonia is an infection of one or both lungs. The tiny air sacs inside the lungs fill with fluid or pus, which makes breathing harder and can lower the amount of oxygen reaching your blood [8][15]. It can be a mild illness that clears up at home or a serious one that needs hospital care, depending on your age, your general health and the germ involved [4][8][9]. In the US, the CDC reports that more than 41,000 people died from pneumonia in 2022 [5], which is why it helps to know the warning signs and who needs to act early.

Symptoms of Pneumonia

The NHS says symptoms can start suddenly or come on gradually over a few days [1]. Health bodies in the UK and US list a similar set of common symptoms [1][3][9]:

• a cough, which may bring up mucus
• a fever, chills or a high temperature
• shortness of breath or wheezing
• chest pain that is worse when you breathe in or cough
• feeling very tired, an aching body and loss of appetite
• feeling sick, vomiting or diarrhea in some people

Pneumonia can be hard to tell apart from a cold or flu at first. The NHLBI, part of the U.S. National Institutes of Health, notes that you may not realize it is more serious until the illness lasts longer than expected [11].

In Older Adults and People With Weakened Immune Systems

Older adults, and people with serious illnesses or weakened immune systems, may not have the typical symptoms [9]. Instead of a fever, they may have a lower than normal temperature. Older adults may also feel weak or become suddenly confused [9], and the NHS notes that confusion is common in older people with pneumonia [1].

In Babies and Young Children

Babies sometimes do not have typical symptoms either. They may vomit, have a fever or cough, or seem restless or tired and without energy [9]. The NHS says babies may make grunting noises when they breathe [1].

The NHLBI says babies may also show these signs of breathing problems [9]:

• a bluish tone to the skin and lips
• grunting
• the muscles between the ribs pulling inward with each breath
• rapid breathing
• the nostrils widening with each breath

If your child is having difficulty breathing, see When to Seek Care below for what the NHS and CDC advise.

The World Health Organization describes the signs health workers look for in children under 5 with a cough or difficult breathing: fast breathing, or the lower chest moving in when the child breathes in [15]. These signs are part of a clinical check by a health worker rather than a home test.

What Causes Pneumonia?

Bacteria and viruses cause most pneumonia, while fungi and parasites are less common causes [1][3]. The NHS adds that fungal pneumonia is rare in healthy people in the UK [1]. Fungi are more likely to cause pneumonia in people with weakened immune systems [10].

Pneumococcus bacteria (Streptococcus pneumoniae) are often named as the most common bacterial cause. The NHLBI says this is true for the United States, and the WHO says the same for children worldwide [10][15]. Common viral causes include flu, the common cold virus, RSV and COVID-19 [3][10]. Pneumonia can also develop after another infection such as a cold or flu [1][10]. If you want to know more about flu itself, see Flu (Influenza): Symptoms, Contagion, and When to Seek Care.

Even so, the cause often stays unknown. The CDC says clinicians are not always able to find out which germ caused someone's pneumonia [3], and the American Thoracic Society says that for most patients the germ is never identified [16].

Pneumonia can also happen when something such as food or water goes down into the lungs instead of the stomach. This is called aspiration pneumonia [1]. Conditions that affect coughing or swallowing, such as a stroke, a head injury, dementia or Parkinson's disease, raise this risk [10]. You can read more about stroke in Stroke: Symptoms, Causes, Diagnosis, Treatment, and Prevention (Complete Guide).

Doctors also describe pneumonia by where it was caught. Most people catch it in the community from someone else [10]. Pneumonia that starts during or after a stay in a hospital or other healthcare setting is described separately, because the germs involved tend to be different [3]. In England, NICE counts pneumonia that develops 48 hours or more after admission to hospital as hospital-acquired [2].

What Is Walking Pneumonia?

"Walking pneumonia" is a popular name, not a separate disease. It usually refers to a milder pneumonia caused by bacteria called Mycoplasma pneumoniae [10]. The CDC explains that people with this type can seem better than expected for someone with a lung infection, so they may not stay home or in bed [7]. Common symptoms are a cough, feeling tired, fever and chills, and shortness of breath. Symptoms can take 1 to 4 weeks to appear after exposure and can last for several weeks [7].

Most Mycoplasma infections are mild, and most people with a mild infection recover without medicine [7]. The CDC says to seek medical care if you or your child has symptoms that persist or get worse, such as wheezing [7].

Who Is More Likely to Get Pneumonia?

Anyone can get pneumonia, but some groups are more likely to get it or to become seriously ill.

Age is one of the biggest factors, although health bodies draw the lines differently. The CDC names adults 65 or older and children younger than 5, with risk rising further at the older and younger ends of those ranges [4]. The NHLBI names adults 65 or older and children 2 years or younger, with higher risk for babies born early [10]. The NHS says some people are more at risk of becoming seriously ill, including people over 65, people with heart disease or a long-term lung condition, and babies and young children [1].

Other things that raise risk include [4][10]:

• long-term lung disease, such as asthma or COPD
• long-term heart disease, liver disease or kidney disease
• diabetes or sickle cell disease
• a weakened immune system, since some conditions and medicines can weaken the immune system
• conditions that make it hard to cough or swallow
• smoking, drinking too much alcohol or using drugs
• being in hospital, especially in intensive care or on a ventilator
• living or working in crowded places, or being around people who are sick

The CDC lists fall and winter as times of higher risk, when the germs that cause respiratory illness spread more, but pneumonia can happen at any time of year [4]. For more on one of the long-term conditions above, see Diabetes: Causes, Symptoms, Diagnosis, Complications, and Modern Treatment (Complete Guide).

How Pneumonia Is Diagnosed

Diagnosis is based on your medical history, a physical exam and, often, some tests [11]. Your doctor will ask about your symptoms and when they began, contact with sick people, recent travel, contact with birds or animals, your vaccinations, the medicines you take and whether you smoke. They will check your temperature and listen to your lungs with a stethoscope [11].

Tests that may be used include [11]:

• a chest X-ray, which is often used to diagnose pneumonia
• blood tests
• a pulse oximeter, a small sensor on your finger or ear that measures the oxygen in your blood

NICE notes that these oxygen sensors may be less accurate in people with darker skin [2]. If you are in hospital, very sick, older or have other health problems, doctors may also test a sample of the mucus you cough up, check your blood for infection, or use a CT scan to look more closely at the lungs [11].

In England, NICE guidance says family doctors can diagnose pneumonia from symptoms and an exam without an X-ray. Doctors combine their own judgement with a short score that checks confusion, breathing rate, blood pressure and age to help decide whether someone can be cared for at home [2]. This score is a tool for clinicians, not a self-test.

How Pneumonia Is Treated

The NHLBI says treatment depends on your risk factors and how serious the pneumonia is, and many people recover at home [12]. Bacterial pneumonia is usually treated with antibiotics a clinician prescribes [1][15]. Antibiotics do not work on viral pneumonia [16]. For viral and fungal pneumonia, your clinician will advise on the right treatment for you [12].

Some people need hospital care. The NHS says this may be needed for people in those higher-risk groups, or if you are very unwell or not getting better after treatment [1]. In hospital, care can include oxygen, fluids through a drip and, in very serious cases, a ventilator to help with breathing [1][12]. In England, NICE says some adults may be offered hospital-level care at home instead, as a shared decision [2].

At home, the NHS and NHLBI both advise rest, plenty of fluids and not smoking [1][13]. The NHS also suggests staying at home while you have a high temperature or do not feel well enough for normal activities [1]. To protect others, cover your mouth and nose when you cough or sneeze, throw tissues away quickly and wash your hands regularly [1].

Recovery: What to Expect

Recovery times vary, and health bodies describe them differently:

• The NHS says most people get better in 2 to 4 weeks, depending on their symptoms [1].
• The NHLBI says some people feel better in 1 to 2 weeks. For others, it can take a month or longer, and most people continue to feel tired for about a month [13].
• A 2019 American Thoracic Society fact sheet says it often takes 6 to 8 weeks to return to normal functioning after pneumonia [16].

NICE guidance in England gives adults a step-by-step picture after starting treatment for pneumonia caught in the community. By 1 week the fever should have gone. By 4 weeks chest pain and phlegm should be much better. By 6 weeks cough and breathlessness should have eased a lot. By 3 months most symptoms should be gone, though tiredness may remain, and by 6 months most people feel back to normal [2]. For most children, NICE says fever and breathing difficulty settle within 3 to 4 days of starting treatment, and a cough may last up to 4 weeks [2].

Talk with your doctor about when you can return to your usual activities and how much physical activity is right for you [13]. Some people are offered pulmonary rehabilitation or physical therapy to help them recover [13].

NICE does not recommend a routine follow-up chest X-ray after leaving hospital. It suggests considering one at about 6 weeks for people with risk factors for lung disease, such as people who smoke or are over 50, and for people whose symptoms persist or who have unexplained weight loss [2]. Ask your doctor whether you need follow-up care and when to schedule it [13]. Early warning signs of lung cancer are covered separately in Lung Cancer Symptoms and Early Warning Signs.

Serious complications are more likely in children, older adults and people with other serious conditions, and when pneumonia is not treated. They include breathing failure, fluid or pus around the lungs, and sepsis, which happens when the infection spreads into the blood [13].

When to Seek Care

In the UK (NHS) [1]:

Ask for an urgent GP appointment or get help from NHS 111 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 you breathe or cough
• feel short of breath

Call 999 or go to A&E if:

• you are struggling to breathe, such as choking, gasping or being unable to speak
• you have pale, blue or blotchy skin, lips or tongue
• you are coughing up blood
• you suddenly feel confused
• you cannot wake your baby, or they feel floppy

The NHS advises not to drive yourself to A&E. Ask someone to drive you, or call 999 for an ambulance [1].

If you have been given antibiotics for pneumonia, the NHS says to contact your doctor if you do not feel any better after taking them for 2 to 3 days [1].

If you are being treated at home in England (NICE) [2]:

NICE says to get further advice if symptoms get worse quickly or a lot, do not start to improve within 3 days, or the person becomes generally very unwell [2]. For children, get advice if a fever continues along with harder breathing, drinking less (or feeding poorly in babies), or tiredness that does not lift.

In the US (CDC and NHLBI):

The CDC says to always seek medical care right away if you or your child is having difficulty breathing [7]. The NHLBI says to see a healthcare provider right away if your symptoms get worse [8], and to call your provider if your symptoms suddenly get worse or you have trouble breathing or talking [13]. If you have other concerns about pneumonia, the CDC advises talking to a healthcare provider [3].

Preventing Pneumonia

Vaccines can help prevent some types of pneumonia, although they cannot prevent every case [6][14]. In the UK, the NHS lists the pneumococcal vaccine, flu vaccine, RSV vaccine and COVID-19 vaccine as helping to protect against infections that can cause pneumonia [1]. In the US, the CDC also names vaccines against several bacteria and viruses that can cause pneumonia [5]. For children, the WHO says immunization against the main causes is the most effective way to prevent pneumonia [15]. Recommendations depend on your age and health, so ask your doctor which vaccines are recommended for you [6].

Everyday habits help too [1][5][14]:

• do not smoke, and limit contact with cigarette smoke
• wash your hands regularly
• stay away from people who are sick, and stay away from others when you are sick
• cough or sneeze into a tissue or your elbow
• keep long-term conditions such as asthma well controlled

If you or someone you care for has trouble swallowing, ask the care team about ways to lower the risk of food or drink going into the lungs [14].

Conclusion

Many people with pneumonia recover at home, but recovery can take weeks, and tiredness can linger after the cough fades. Pace yourself as you get back to normal life, and keep in touch with your doctor if recovery stalls. Between illnesses, staying up to date with vaccines and not smoking are practical steps you can take.

Medical Disclaimer

This article is for general information and does not replace advice from a qualified health professional. If or someone with you is struggling to breathe, get emergency help straight away.