Pneumonia: symptoms, contagion, walking pneumonia

In short

• Pneumonia is an infection of one or both lungs. Bacteria and viruses are the most common causes.
• The usual signs are cough, fever or chills, fatigue, chest pain when breathing or coughing, and shortness of breath. Older adults may have milder signs or mainly confusion.
• 'Walking pneumonia' describes a mild case in which a person feels well enough to keep going. It still needs to be taken seriously if it drags on or worsens.
• The germs behind pneumonia can pass from person to person, so staying home while sick and washing hands matters.
• Vaccines against pneumococcus, flu, COVID-19 and RSV lower your chance of a serious lung infection.

What pneumonia is

Your lungs end in tiny air sacs called alveoli, where oxygen passes into the blood. In pneumonia those sacs fill with fluid or pus. Breathing becomes harder and less oxygen gets in. The CDC notes that bacteria and viruses are the most common causes, and fungi and parasites are less common.

Severity ranges from mild to life-threatening, depending on the germ, your age and your overall health. Doctors also sort pneumonia by where it started: in the community, during or after a stay in a healthcare facility, or while on a breathing machine. The germs differ between those settings, which is one reason treatment choices differ too.

The term 'walking pneumonia' is not a medical diagnosis. The CDC explains that it was coined for mild pneumonia caused by the bacterium Mycoplasma pneumoniae, because people with it often seem better than expected and keep up normal activities. Symptoms can appear 1 to 4 weeks after exposure and last several weeks.

Symptoms and look-alikes

The CDC lists the typical symptoms of pneumonia:

• Cough, sometimes with phlegm
• Fever or chills
• Shortness of breath
• Chest pain when you breathe in or cough
• Fatigue
• Nausea, vomiting or diarrhea
• Confusion or other changes in mental status

Not everyone looks the same. MedlinePlus notes that newborns may show no signs, and that older adults may have milder symptoms, a lower-than-normal body temperature, weakness or confusion. In young children, mycoplasma infection can also look like sneezing, a runny nose, wheezing or an upset stomach.

Several illnesses overlap with pneumonia, and the exam is what separates them. These pointers help you decide how quickly to be seen:

• Common cold: a runny nose, sore throat and mild cough that gradually improve. A cold that suddenly gets worse, or brings breathlessness or chest pain, is a reason to call.
• Flu and COVID-19: both can come with fever, body aches and cough, and both can themselves lead to pneumonia, according to the CDC. New shortness of breath or a fever that returns after you seemed to improve is the warning sign.
• Chest cold from mycoplasma: the CDC describes tiredness, headache, a slowly worsening cough and sore throat as the most common form, with true pneumonia less common.
• Aspiration: coughing after food or liquid goes down the wrong way can cause pneumonia, particularly in people who have trouble swallowing.

What to do right now

1. Check your breathing firstIf you are struggling for breath, cannot speak a full sentence, or your lips look blue or gray, call 911 instead of reading further.
2. Call your primary care provider todayA cough with fever, chills, chest pain or breathlessness should be examined. A same-day visit or urgent care is reasonable if your own clinician cannot see you.
3. Rest and drink fluidsKeep up with fluids and rest while you wait to be seen. Do not smoke, because smoking is a listed risk factor for pneumonia.
4. Do not take leftover antibioticsAntibiotics work on bacteria, not viruses, and MedlinePlus states that they do not treat viral pneumonia. Only a clinician can decide whether they are the right class of medicine for you.
5. Stay home and limit contactCover coughs and sneezes, wash your hands often and keep away from babies, older relatives and anyone with a lung or heart condition until you have been checked.
6. Watch for worseningIf you feel worse, get more breathless or are not improving after starting treatment, contact your clinician again straight away. The NHS advises seeking advice if you have not improved after 2 to 3 days of antibiotics.

Causes, risk factors and whether it is contagious

Common bacterial causes include pneumococcus and Mycoplasma pneumoniae. Viral causes include influenza, COVID-19, RSV, rhinovirus and others. Fungal pneumonia mostly affects people with chronic illness or weakened immune systems. Doctors cannot always say which germ is responsible in a given case.

Is pneumonia contagious? The infections that cause it can spread. For mycoplasma, the CDC says people spread it through coughing or sneezing. Catching a germ does not always mean developing pneumonia, because the same exposure may give someone else only a cold. People with the risk factors below are more likely to end up with a lung infection.

Risk factors listed by MedlinePlus include:

• Age under 2 or 65 and older
• Smoking and heavy drinking
• Lung disease, a weakened immune system, or trouble coughing or swallowing
• Chronic conditions such as diabetes, heart failure, sickle cell disease, and liver or kidney disease
• A recent cold or flu, or a hospital stay, especially in intensive care
• Exposure to toxic chemicals or pollutants and malnutrition

Red flags: when to call 911

Call 911 or go to the nearest emergency room if you or someone with you has any of the following. Do not drive yourself if you are short of breath.

• Severe difficulty breathing, or breathing that is fast and labored
• Blue, gray or blotchy lips, tongue or skin
• Coughing up blood
• Sudden confusion, or being unusually sleepy and hard to wake
• A baby who is floppy, cannot feed or cannot be woken

MedlinePlus lists bloodstream infection, lung abscesses, fluid around the lung and respiratory failure among the complications. That is why a pneumonia that is getting worse should never be waited out at home.

How a clinician confirms pneumonia

The NHLBI says a provider reviews your history, examines you and listens to your lungs, then orders tests to determine the type of pneumonia. The most common test is a chest X-ray.

• Chest X-ray to show where the infection is
• Blood tests, such as a complete blood count and blood culture
• Pulse oximetry, which measures the oxygen level in your blood
• For more serious cases: a sputum test, chest CT scan, pleural fluid culture or bronchoscopy

You do not need to interpret any of these numbers yourself. Ask your clinician what the results mean for your plan.

Treatment and recovery

Treatment depends on the cause and on how sick you are. MedlinePlus explains that antibiotics treat bacterial pneumonia and some fungal types, antivirals may be used for certain viral cases, and antifungal medicines treat other fungal types. Severe cases may need hospital care with intravenous antibiotics and oxygen therapy.

The CDC says most people with a mild mycoplasma infection recover on their own without medicine, although clinicians routinely treat pneumonia from this bacterium with antibiotics and some strains resist certain antibiotics. For symptom relief, ask a clinician or pharmacist which over-the-counter products suit you.

If you are prescribed antibiotics, the NHS advises finishing the full course as directed. It also advises against cough medicine because coughing helps clear the infection. Recovery varies: MedlinePlus says it can take a week or more than a month, and the NHS says most people feel better within 2 to 4 weeks. Tiredness and a lingering cough can outlast the infection.

Prevention, and who needs extra care

The CDC says pneumonia can often be prevented. Vaccines protect against some of the bacteria that cause it, such as pneumococcus, Haemophilus influenzae type b and pertussis, and against viruses including flu, COVID-19, RSV, measles and chickenpox. Healthy habits also help: washing hands, avoiding sick people, covering coughs, not smoking and keeping chronic conditions such as asthma under control.

The CDC recommends pneumococcal vaccination for all children younger than 5, for children 5 through 18 with certain risk conditions, for all adults 50 and older, and for adults 19 through 49 with certain risk conditions. Ask your primary care provider or pharmacist what you are due for.

• Babies and young children: fast breathing, grunting, poor feeding or unusual sleepiness need same-day care.
• Adults 65 and older: confusion, weakness or a low temperature can be the main signs, so a change in behavior is enough reason to call.
• People with heart disease, lung disease or diabetes: the NHS lists them as more likely to become seriously ill, so contact a clinician early.
• Pregnancy: a cough with fever or breathlessness should be assessed promptly so that treatment is chosen with your obstetric clinician.

Myths and facts

• Myth: Pneumonia is just a bad cold. Fact: it is an infection of the lungs in which the air sacs fill with fluid or pus, and it can be serious.
• Myth: Walking pneumonia is harmless. Fact: it is often mild, but symptoms can last several weeks and serious complications, though uncommon, can occur.
• Myth: Antibiotics always fix it. Fact: they work against bacteria and some fungi, not against viral pneumonia.
• Myth: Only older people get pneumonia. Fact: anyone can, but children under 2 and adults 65 and older are at higher risk.

Questions and answers

Sources

1. CDC — About Pneumonia
2. CDC — Preventing Pneumonia
3. CDC — About Mycoplasma pneumoniae Infection
4. CDC — Pneumococcal Vaccine Recommendations
5. NHLBI — Pneumonia
6. MedlinePlus — Pneumonia
7. NHS — Pneumonia

Sources checked on 30 October 2026.