How is it Diagnosed?
Influenza (flu) is primarily diagnosed based on clinical symptoms and confirmed with
laboratory tests, particularly during flu season or outbreaks. Patients typically present
with sudden onset of fever, chills, sore throat, dry cough, headache, fatigue, and
myalgia.
A clinical diagnosis is often sufficient in otherwise healthy individuals with typical
symptoms. However, laboratory confirmation is vital in hospitalized patients, high-risk
groups (e.g., elderly, pregnant women, immunocompromised), or atypical presentations.
The most common diagnostic tests are Rapid Influenza Diagnostic Tests (RIDTs), which
detect viral antigens in respiratory samples within 10–15 minutes. However, their
sensitivity can be low, especially for Influenza B.
Reverse Transcription Polymerase Chain Reaction (RT-PCR) is the gold standard test for
influenza diagnosis due to its high sensitivity and specificity. It can also distinguish
between different influenza virus types and subtypes.
Other diagnostic options include viral culture and direct fluorescent antibody (DFA)
staining, though these are less commonly used due to longer processing times.
Nasopharyngeal or throat swabs are standard specimens for testing. In severe cases or
outbreaks, chest X-rays may be performed to assess for complications like pneumonia.
Early and accurate diagnosis is crucial for initiating antiviral therapy (e.g., oseltamivir)
and implementing public health measures. Vaccination history, recent exposure, and
epidemiologic context are also considered when diagnosing influenza.