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Understanding Community-Acquired Pneumonia

Medically reviewed by Nick Villalobos, MD — By Erica Cirino and The Healthline Editorial Team on September 26, 2022Pneumonia is an infection in one or both lungs. Bacteria and viruses typically cause pneumonia. Fungi can also cause some types of pneumonia. Pneumonia affects millions of people around the world each year. In the United States, about 25 of every 10,000 people get pneumonia each year. That rate gets higher as age increases. Some people develop a serious case of pneumonia while in the hospital. But it’s more common to develop pneumonia outside a hospital setting. When this happens, doctors refer to it as community-acquired pneumonia (CAP). CAP is the most common type of pneumonia people experience. Although it’s not usually as serious as hospital-acquired pneumonia (HAP), it can still have serious complications. This article will look at CAP, how it compares with other types of pneumonia, and what you can do to protect yourself.

Types of pneumonia

Community-acquired pneumonia (CAP): CAP refers to pneumonia you develop outside a hospital setting.Hospital-acquired pneumonia (HAP): Also called nosocomial pneumonia, HAP occurs if you fall ill with pneumonia 48 hours or more after your admission to the hospital. HAP is usually more serious than CAP because it can involve bacteria that are resistant to antibiotics.Ventilator-associated pneumonia (VAP): A subgroup of people with HAP may develop VAP. It occurs in hospital patients who are receiving mechanical ventilation for respiratory failure.

What causes community-acquired pneumonia

Pneumonia has many causes. Research from 2017 references 26 common causes of CAP, mainly bacteria and viruses. Some fungi can also cause CAP. The most common causes of CAP in the United States are:human rhinovirus (common cold)influenza virus (flu)Streptococcus pneumoniae Other common causes include:the coronavirus SARS-CoV-2 (COVID-19)Haemophilus influenzaeLegionella bacteriaMycoplasma pneumoniahard-to-detect bacteria, such as Chlamydia pneumoniae So, how do humans come in contact with these germs? Some of them, like Streptococcus pneumoniae, already live in your nose, sinuses, or mouth. They can eventually spread to your lungs, where they cause disease. It’s unclear why they invade the lungs. You might also breathe in these germs if they are in the air around you. Certain activities or environments may increase your risk of coming in contact with them.

Who is at risk of community-acquired pneumonia

CAP and its complications are most likely to affect:adults older than age 65people with existing health conditionspeople with a weakened immune systempeople who smokepeople who are malnourished Children younger than 5 years also have a higher risk of CAP, as well as those who may interact with them in day care settings.

Health conditions

Certain conditions may increase your risk of developing CAP. According to a 2017 review of 29 studies, these include:chronic bronchitis or COPDasthmadiseases of the mouth, teeth, or gumsconditions that cause impaired function While the review was inconclusive on whether heart disease was a risk factor, other research from 2015 suggests it is. Other conditions, such as diabetes and liver disease, may affect your outlook with CAP. Researchers in the 2017 review also identified certain medications that may increase your risk:immunosuppressantsoral steroidsproton pump inhibitors and H2 blockers (both used to treat gastric reflux)

Environmental exposure

According to the World Health Organization, environmental factors may also affect your risk of CAP. These include:indoor air pollution from biomass fuelscrowded homessecondhand smokeliving on or near a farm with livestockliving near centers of industrial food animal production According to 2015 research, people who smoke cigarettes also have a higher risk of CAP.

Zoonotic animal exposure

Exposure to certain animals that may carry the germs that cause CAP could put you at risk. According to research from 2016 and 2017, examples include:birds, including poultryrabbitsgoatssheeppigscattlesick dogscats in labor

Travel exposure

The germs that cause CAP exist everywhere in the world. But some regions are more likely to have certain germs. Experts know that travel to large gatherings abroad contributes to the spread of germs that cause CAP. Traveling, spending time on a cruise ship, or staying in a hotel can increase your risk of exposure to these germs. If you have symptoms of pneumonia, be sure to tell a doctor of any recent travel. It may help them make a diagnosis.

What are the symptoms of community-acquired pneumonia

Pneumonia is a serious, sometimes fatal disease. The main symptoms of CAP include:coughproduction of sputumfeverdifficulty breathingheadachechest painmuscle achesirritability and restlessness (in infants)confusion (in older adults) In some people, breathing issues and fluid buildup in the lungs may become severe. This may lead to respiratory failure and the need for oxygen therapy or mechanical ventilation.

How do doctors diagnose community-acquired pneumonia

If a doctor notices you have symptoms of CAP, they will likely perform or order the following:Medical history: A doctor will ask about your medical history to better understand how you may have become ill.Physical exam: A doctor will perform a physical exam to check for fever and lung sounds consistent with pneumonia.Chest X-ray: A chest X-ray can show any fluid buildup or inflammation in the lungs.CT scan: A doctor might use a CT scan to confirm a diagnosis or rule out other conditions. CT scans may be more effective at detecting pneumonia than chest X-rays, but they are more expensive and take longer.Complete blood count (CBC): A CBC can help doctors see whether your immune system is fighting the infection.Electrolyte panel: An electrolyte panel can check your electrolyte levels as well as your kidney and liver function.Blood, sputum, or urine tests: Blood and sputum cultures, as well as urine antigen tests, may identify the exact cause of the infection, influencing treatment.Molecular testing: This is the standard way to test for viral pneumonia, such as cases caused by COVID-19. Research from 2020 has also shown that molecular tests, like polymerase chain reaction (PCR) tests, may also be better than cultures at detecting bacterial pneumonia. A doctor will also consider other potential diagnoses. Some illnesses with symptoms similar to CAP include:acute bronchitis or other respiratory infectionchronic obstructive pulmonary disease (COPD)heart failure or heart attackpulmonary embolism (blood clot in your lung)tuberculosis

What is the treatment for community-acquired pneumonia

If you have CAP, your treatment plan will depend on your symptoms and the specific cause of your infection. A doctor will also consider how severe your symptoms are. According to 2017 research, 80% of people in the United States can treat CAP at home. If your doctor determines you have a milder case of CAP from bacteria, they may prescribe antibiotics for you to take at home. A doctor will likely prescribe one of the following:amoxicillinazithromycinclarithromycindoxycycline It’s important to take antibiotics as prescribed. If you don’t follow the proper regimen, the bacteria could become antibiotic resistant. If you have a more severe case of CAP, you may need to get treatment in a hospital. Healthcare professionals can provide a variety of intravenous (IV) antibiotic treatments based on your specific situation at a hospital. But antibiotics do not work for cases of viral pneumonia. You may need to let the virus run its course. In some cases, you may be able to use antiviral medication. Examples include:remdesivir (Veklury) for COVID-19oseltamivir (Tamiflu) for influenzainhaled ribavirin for respiratory syncytial virus (RSV) There are other actions you can take to manage symptoms of viral CAP:Take over-the-counter pain relievers, like acetaminophen or ibuprofen, to reduce fever.Drink plenty of fluids to stay hydrated.Get enough rest to allow your body to recover.Quit smoking if you regularly smoke. If your symptoms are severe, you may need to go to the hospital. Additional treatments in the hospital may include:oxygen therapyintravenous (IV) fluidsrespiratory support with a ventilator

What are the potential complications of community-acquired pneumonia

With CAP comes the risk of possible complications. These are more likely if doctors don’t make a timely diagnosis or if initial treatments don’t work. Possible complications include:Pleural effusion: Pleural effusion is the buildup of fluid in your pleura, the space between your lungs and chest wall.Empyema: Empyema is the buildup of pus in the pleural space.Lung abscesses: An abscess is a pus-filled cavity that, in this case, forms in your lung.Sepsis: Sepsis is an extreme immune response to an infection.Acute respiratory distress syndrome (ARDS): ARDS occurs when the lungs become severely inflamed and fill with fluid, preventing oxygen from getting into the blood. Complications like sepsis and ARDS can cause organ failure and death.

What is the outlook for people with community-acquired pneumonia

With rapid and appropriate treatment, many people fully recover from CAP without complications. Young people tend to recover fully more quickly. If CAP is due to bacteria, you may start to feel better within 5 to 7 days of starting antibiotics. Still, it can take months for all your symptoms to resolve. If you have a mild case of CAP, full recovery is possible with rest, antibiotics or antivirals, and sleep. More severe cases of CAP may require lengthy hospital stays to help keep you stable and aid recovery. For people admitted to intensive care, the death rate can be as high as 23%, according to 2021 research.

How can I prevent community-acquired pneumonia

Taking precautions against illness, such as getting an annual flu shot, can reduce your risk of CAP. The Centers for Disease Control and Prevention (CDC) recommends that people ages 65 and older get a high dose flu vaccine. People over 65 can also consider getting the pneumococcal vaccine to prevent CAP. This is especially important if you have other health conditions or if you smoke. You may need a booster shot if you received your vaccine before age 65, or if you have a weakened immune system. Other everyday actions you can do to help prevent disease include the following:Wash your hands frequently, especially after using the bathroom or being in public.Cough into your elbow when you need to cough.Keep a physical distance from people who are ill.If you smoke or vape, consider quitting to reduce damage to your lungs. Such damage can make you more vulnerable to pneumonia infection.

Takeaway

Community-acquired pneumonia (CAP) is the most common type of pneumonia. The term refers to pneumonia that you contract outside of a hospital setting. While many people recover from CAP with rest and antibiotic or antiviral treatment, it can be especially serious for older adults and people with existing health conditions. Potential complications of CAP can be life threatening. But people in high risk groups can take precautions against severe disease, such as getting an annual flu shot. Last medically reviewed on September 26, 2022

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ncbi.nlm.nih.gov/pmc/articles/PMC6280505/Our experts continually monitor the health and wellness space, and we update our articles when new information becomes available. Current Version Sep 26, 2022 By Erica Cirino, The Healthline Editorial Team Edited By A. L. Heywood Medically Reviewed By Nick Villalobos, MD Copy Edited By Sara Giusti Share this articleMedically reviewed by Nick Villalobos, MD — By Erica Cirino and The Healthline Editorial Team on September 26, 2022

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