Causes and Risk Factors
Pneumonia develops when germs get past the body's defenses and infect the lungs:- Bacteria: Streptococcus pneumoniae (pneumococcus) is the most common bacterial cause in adults; "atypical" bacteria such as Mycoplasma cause a milder walking pneumonia.
- Viruses: Influenza, COVID-19, RSV, and other respiratory viruses can cause pneumonia directly or open the door to a bacterial infection.
- Aspiration: Food, liquid, or stomach contents inhaled into the lungs can trigger infection, especially in people with swallowing problems.
- Higher-risk groups: Risk rises with age over 65, smoking, and chronic conditions such as COPD, asthma, bronchiectasis, diabetes, heart disease, and weakened immunity.
Symptoms
- Cough: Often producing yellow, green, or rust-colored phlegm.
- Fever, chills, and sweats: Sometimes with shaking chills; older adults may instead have confusion or a low body temperature.
- Shortness of breath: With everyday activity or even at rest.
- Chest pain: Sharp pain that worsens with deep breathing or coughing.
- Fatigue and poor appetite: Weakness can linger for weeks after treatment.
Diagnosis
Your doctor listens for crackles in the lungs and typically confirms the diagnosis with a chest X-ray. Pulse oximetry checks oxygen levels, and blood tests or sputum cultures may identify the germ; rapid swabs can detect influenza and COVID-19 when a virus is suspected. Severity scoring based on age, vital signs, and lab results helps decide whether treatment at home is safe or hospital care is needed — most otherwise-healthy adults can be treated at home.Treatment
- Antibiotics: Bacterial pneumonia is treated with oral antibiotics such as amoxicillin-clavulanate, azithromycin, or doxycycline, chosen based on age, health conditions, and local resistance patterns; respiratory fluoroquinolones such as levofloxacin are reserved for selected patients. Most people improve within a few days of starting treatment.
- Supportive care: Rest, fluids, and fever reducers help recovery; viral pneumonia may also be treated with antivirals when appropriate.
- Hospital care: Needed when oxygen levels are low, blood pressure drops, or the infection is severe.
Recovery
Fever usually settles within a few days of effective treatment, but fatigue and a lingering cough commonly last several weeks — recovery is a marathon, not a sprint, especially after age 65. Finish the entire antibiotic course even if you feel better, rest, and return gradually to activity. Your doctor may repeat a chest X-ray after six to eight weeks in smokers and older adults to confirm the infection has fully cleared and that no underlying abnormality was hiding behind it.Prevention
Pneumococcal vaccines are recommended for all adults 50 and older and younger adults with chronic conditions. Yearly flu vaccination, COVID-19 vaccination, RSV vaccination for eligible older adults, quitting smoking, and good hand hygiene all reduce risk.When to Seek Immediate Care
Seek emergency care for difficulty breathing, chest pain, bluish lips, confusion, or a fever above 103°F that does not respond to medication. If a cough and fever are not improving — or a cold suddenly worsens — do not wait it out. Zimmer Medical Group's primary care team in St. Petersburg diagnoses and treats pneumonia and keeps patients current on pneumococcal vaccination — schedule a visit today.Recovering From Pneumonia and Preventing the Next One
Most pneumonia is treated at home, and the outcome depends less on which antibiotic was chosen than on what happens in the first three days, whether recovery is given time, and whether the episode prompts the vaccines that prevent the next one.
The first 72 hours on antibiotics
Amoxicillin-clavulanate paired with azithromycin or doxycycline covers both the typical and the atypical bacteria, and fever should break and breathing ease within two to three days. No improvement by the third day, or any worsening, is the signal to be seen again rather than to wait out the course, because it can mean a resistant organism, fluid collecting around the lung, or a diagnosis that was never pneumonia. For uncomplicated pneumonia, five days is generally enough once you have been stable and fever-free for two of them. Levofloxacin is reserved for people who cannot take the first-line drugs, because of its tendon and nerve side effects.
Recovery takes longer than the antibiotics
The cough can persist for a month or more and fatigue for six weeks, especially after 65, and neither means the infection is back. Fluids, acetaminophen for fever and chest-wall pain, sleeping propped up, and short walks several times a day help; heavy cough suppressants mostly do not, because clearing the phlegm is part of recovery. Anyone discharged from the hospital with pneumonia benefits from a visit within a week; our discharge follow-up article explains why.
What pneumonia is confused with
Acute bronchitis produces a similar cough without the fever, breathlessness, and chest X-ray changes, and does not need antibiotics. Fluid in the lungs from heart failure, a pulmonary embolism, and a flare of asthma or COPD can all look like pneumonia, which is why an X-ray and an oxygen reading come before the prescription. When influenza is the trigger, oseltamivir is added within two days of symptoms.
The follow-up X-ray and what it is for
In smokers and adults over 50, a chest X-ray six to eight weeks after recovery confirms the shadow has cleared; one that has not is investigated, because a tumor or a blocked airway can present as pneumonia that will not resolve. Two episodes in the same part of the lung within a year, or a cough lasting past eight weeks, deserves the same look; our chronic cough workup article covers it. Long-term smokers who qualify should also be in low-dose CT screening.
Vaccines and the risks that can be changed
A single dose of a conjugate pneumococcal vaccine is now recommended for every adult at 50, and earlier with a chronic condition; our pneumococcal vaccine update explains which one. Yearly flu, updated COVID-19, and RSV vaccination for eligible older adults each prevent the viral illness that opens the door to bacterial pneumonia. Treating nicotine dependence, limiting alcohol, and having swallowing checked after a stroke reduce risk in ways antibiotics cannot. Our pulmonary team manages recovery and screening. The NHLBI and the American Lung Association publish patient guidance on treatment and recovery.
If you were treated for pneumonia and are not improving by the third day, or have never had a pneumococcal vaccine, schedule a visit.