Diagnosis and Treatment of Influenza

Diagnosis

After an influenza alert has been issued, if a patient complains of typical influenza-like symptoms, influenza can be clinically suspected. Influenza-like illness is defined as having a fever of 37.8˚C or higher and one respiratory symptom such as cough, sore throat, or runny nose. In Korea, the influenza alert is issued by the Korea Centers for Disease Control and Prevention around November or December, and after that, about 70% of patients with influenza-like symptoms can be clinically diagnosed with influenza.

Treatment

Treatment for influenza can be divided into antiviral therapy and other symptomatic treatment. In particular, influenza in the elderly, infants and young children, and patients with chronic internal medicine diseases carries an increased risk of serious complications such as pneumonia, hospitalization, and death, so early antiviral treatment is very important.

1. Antiviral agents There are two types of antiviral agents that are effective against the influenza virus. Adamantane agents (amantadine, rimantadine), which are effective only against influenza A, and neuraminidase inhibitors such as Tamiflu and Relenza, which are effective against both influenza A and B.

The antiviral agents currently widely used for the treatment of influenza are Tamiflu and Relenza. Tamiflu has the advantage of being taken orally from age 1 and above, with the drug absorbed systemically to exert its effect. If both drugs are administered within 2 days of symptom onset, they can shorten the duration of symptoms such as high fever by 1 to 1.5 days, helping patients return to normal life earlier. They can also reduce the incidence of otitis media in children and decrease the number of times antibiotics are used. Antiviral treatment has also been reported to reduce the frequency of lower respiratory tract complications, and early antiviral treatment is known to have a greater effect in reducing treatment burden and complications, especially in elderly patients and those with chronic internal medicine diseases.

Because the side effects of antiviral agents differ by drug, careful observation is necessary. 5-10% of patients taking amantadine experience mild central nervous system side effects such as agitation, anxiety, insomnia, or impaired concentration. Tamiflu may cause neuropsychiatric adverse reactions such as abnormal behavior in teenagers, so caution is required. Relenza is an inhaled preparation and may induce bronchoconstriction in patients with asthma and chronic obstructive pulmonary disease, so its use should be avoided. In addition, Relenza is not approved for use in children under 7 years of age.

2. Antibiotic therapy Usually, influenza improves after a fever lasting about 2-3 days, but if high fever persists and cough, yellow sputum, chest pain, or shortness of breath occurs, a complication of pneumonia should be suspected. When an acute bacterial complication such as secondary bacterial pneumonia is suspected or confirmed in a patient with influenza, antibiotic treatment is given. Antibiotics are selected according to Gram stain and culture results using respiratory secretion samples such as sputum or transtracheal aspirate. If the cause of bacterial pneumonia remains unclear even after testing respiratory secretions, an antibiotic effective against the most common causative bacteria (pneumococcus, Haemophilus, Staphylococcus aureus) should be selected and administered.

3. Symptomatic treatment For patients with uncomplicated influenza, acetaminophen may be administered to relieve headache, muscle pain, and fever. However, aspirin should be avoided in children under 18 years of age because of its association with Reye syndrome. Cough usually improves on its own, so cough suppressants are generally not necessary; however, if coughing is severe and problematic, medications containing codeine may be used. During the acute phase, rest and maintain fluid intake, and especially if the course of the illness was severe, return gradually to daily life after recovery.

So far, we have explained the diagnosis and treatment of influenza. In the next part, we will look at the prevention of influenza.

Source: Korea Centers for Disease Control and Prevention National Health Information Portal