Influenza is an acute respiratory infectious disease caused by the influenza virus. It is highly contagious and spreads rapidly, making it extremely prone to widespread outbreaks. Experts recommend that everyone understand its common symptoms and diagnostic criteria to better prevent the disease. Below are methods for differential diagnosis of influenza.
Differential diagnosis of influenza
It is mainly differentiated from influenza-like illness (IL1) caused by various viruses, bacteria, and other pathogens other than influenza virus. Diagnosis requires laboratory tests, such as pathogen isolation, serological examination, and nucleic acid testing.
1. Common cold
The common cold can be caused by a variety of respiratory viruses. In addition to collecting epidemiological data, influenza usually has more severe systemic symptoms than the common cold, while the local respiratory symptoms of the common cold are more prominent.
2. Severe Acute Respiratory Syndrome (SARS)
SARS is a highly contagious pneumonia caused by the SARS coronavirus, which can affect multiple organs and systems. Clinically, it is mainly characterized by systemic symptoms such as fever, fatigue, headache, and muscle and joint pain, as well as respiratory symptoms such as dry cough, chest tightness, and difficulty breathing. Its clinical manifestations are similar to those of pneumonia-like influenza. A diagnosis of SARS can be made based on epidemiological history, clinical symptoms and signs, general laboratory tests, chest X-ray findings, a positive SARS pathogen test, and after ruling out other diseases.
3. Mycoplasma pneumoniae infection
Systemic symptoms such as fever, headache, and muscle pain are milder than in influenza, but coughing is more pronounced, sometimes accompanied by a small amount of sticky sputum. Chest X-ray may show increased lung markings, and if pneumonia is present, patchy shadows in the lungs may be seen, indicating interstitial pneumonia. Isolation of Mycoplasma pneumoniae from sputum and throat swabs confirms the diagnosis. Serological tests are helpful for diagnosis, while nucleic acid probes or PCR can aid in early and rapid diagnosis.
4. chlamydial infection
Systemic symptoms such as fever, headache, and muscle aches are milder than those of influenza, but it can cause sinusitis, pharyngitis, otitis media, tracheobronchitis, and pneumonia. Laboratory tests can help in differential diagnosis, including pathogen isolation, serological tests, and PCR testing.
5. Legionella pneumophila infection
The disease is more prevalent in summer and autumn, and is often associated with air conditioning systems and water pollution. The onset is rapid, with chills, fever, headache, and other symptoms. Systemic symptoms are quite pronounced, with respiratory symptoms including cough, thick sputum, hemoptysis, chest tightness, and shortness of breath. A small number of cases may develop into ARDS. Extra-respiratory symptoms are also common, such as diarrhea, mental symptoms, and cardiac and renal dysfunction. Chest X-rays show inflammatory infiltrates. Positive cultures of respiratory secretions, sputum, and blood can confirm the diagnosis, but the detection rate is low. Detection of antigens in respiratory secretions using direct fluorescent antibody assay (DFA) or nucleic acid testing using PCR is helpful for early diagnosis. Indirect immunofluorescence antibody assays in serum and urine are also diagnostically significant.
