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Influenza (Flu)

Influenza is a contagious respiratory virus causing fever, body aches, cough, and fatigue. Yearly vaccination and early antiviral treatment protect those at highest risk of complications.

Pulmonary
Influenza (flu) is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and lungs. Most healthy people recover within one to two weeks, but the flu can cause serious complications — especially in adults over 65, pregnant women, young children, and people with chronic medical conditions. Seasonal epidemics occur every year, typically peaking in the winter months, even in Florida.

Causes and Spread

Influenza spreads mainly through respiratory droplets released when infected people cough, sneeze, or talk. It can also spread by touching contaminated surfaces and then the eyes, nose, or mouth. People are contagious beginning about one day before symptoms start and for several days afterward, which is why the virus moves quickly through households and workplaces.

Symptoms

Unlike a common cold, flu symptoms usually come on abruptly:
  • Fever and chills: Often with temperatures of 100–104°F, though not everyone with flu has a fever.
  • Body aches and headache: Muscle aches are typically prominent.
  • Cough and sore throat: A dry cough may linger for weeks.
  • Fatigue and weakness: Can last well beyond the other symptoms.
  • Runny or stuffy nose: Sometimes with sneezing.
  • Vomiting and diarrhea: More common in children than adults.

Complications

Most complications occur in higher-risk groups, but they can affect anyone:
  • Pneumonia: The most serious common complication, caused by the flu virus itself or by bacteria invading afterward.
  • Worsening of chronic conditions: Flu can trigger asthma attacks, COPD flare-ups, and heart problems, and it makes blood sugar harder to control in people with diabetes.
  • Sinus and ear infections: Common, milder complications.
  • Dehydration: A particular concern for older adults in Florida's heat, since fever and poor intake add up quickly.

Diagnosis

During flu season, doctors often diagnose influenza from symptoms alone. Rapid tests using a nasal swab can confirm the diagnosis in about 15 minutes, which is helpful when the result would change treatment, when symptoms overlap with COVID-19, or when a household member is at high risk and might benefit from preventive antiviral medication.

Treatment

For most healthy adults, rest, fluids, and fever reducers such as acetaminophen are the mainstays. Antiviral medications such as oseltamivir work best when started within 48 hours of symptom onset and can shorten the illness and reduce complications; they are especially important for older adults and people with chronic conditions such as asthma, COPD, diabetes, or heart disease. Antibiotics do not treat the flu because it is caused by a virus.

Prevention

Yearly vaccination is the single best protection. Because circulating strains change, the vaccine is updated annually, and everyone 6 months and older is advised to receive it each fall. Adults 65 and older benefit from higher-dose or adjuvanted vaccines designed to produce a stronger immune response. Frequent handwashing, avoiding close contact with sick people, and staying home while ill also limit spread. In some situations — for example, a high-risk household member exposed to the flu — doctors may prescribe an antiviral preventively.

When to Seek Immediate Care

Seek urgent medical attention for difficulty breathing, chest pain, confusion, persistent dizziness, inability to keep fluids down, or a fever that improves and then returns with a worse cough — the last can signal pneumonia developing after the flu. An annual wellness visit is a convenient time to get your flu shot and review your risk. The primary-care team at Zimmer Medical Group offers seasonal flu vaccination and prompt sick visits during flu season — schedule an appointment to stay protected.

Related Medications

Commonly prescribed medications for this condition

Oseltamivir

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