From the Guidelines
If influenza symptoms persist beyond a week, you should seek medical attention as this may indicate complications or a secondary infection. Most uncomplicated flu cases resolve within 5-7 days, though cough and fatigue can linger for up to two weeks. Persistent or worsening symptoms could signal bacterial pneumonia, sinusitis, or bronchitis. Your doctor may prescribe antibiotics if a bacterial infection is suspected, such as amoxicillin 500mg three times daily for 7-10 days for sinusitis or azithromycin 500mg on day one followed by 250mg daily for 4 days for pneumonia. Antiviral medications like oseltamivir (Tamiflu) are most effective when started within 48 hours of symptom onset but may still be prescribed later for severe cases, as noted in the guidelines from the Advisory Committee on Immunization Practices 1. While waiting for medical care, continue supportive measures including rest, hydration, and over-the-counter fever reducers like acetaminophen or ibuprofen. Watch for warning signs requiring immediate attention: difficulty breathing, chest pain, confusion, severe weakness, or worsening of symptoms after initial improvement. Influenza can suppress your immune system temporarily, making you vulnerable to secondary infections, which is why symptoms lasting beyond a week warrant professional evaluation.
Some possible causes of persistent influenza include:
- Exacerbation of underlying medical conditions, such as pulmonary or cardiac disease, as mentioned in the study by the Advisory Committee on Immunization Practices 1
- Secondary bacterial pneumonia or primary influenza viral pneumonia, as noted in the guidelines from the Advisory Committee on Immunization Practices 1
- Coinfection with other viral or bacterial pathogens, as mentioned in the study by the Advisory Committee on Immunization Practices 1
- Encephalopathy, transverse myelitis, Reye syndrome, myositis, myocarditis, and pericarditis, which have been associated with influenza infection, as reported in the study by the Advisory Committee on Immunization Practices 1
It is essential to seek medical attention if you experience any of the following:
- Difficulty breathing
- Chest pain
- Confusion
- Severe weakness
- Worsening of symptoms after initial improvement
Early antiviral treatment can reduce the risk of complications from influenza, and treatment should not be delayed while awaiting diagnostic test results, as recommended by the Advisory Committee on Immunization Practices 1. Empiric antiviral treatment is often necessary, and providers should not delay initiation of treatment while awaiting confirmatory diagnostic tests results or if specimens are not obtained, as noted in the guidelines from the Advisory Committee on Immunization Practices 1.
In areas with limited antiviral medication availability, local public health authorities might provide additional guidance about prioritizing treatment within groups at higher risk for complications, as mentioned in the study by the Advisory Committee on Immunization Practices 1. Current CDC guidance on treatment of influenza should be consulted, and updated recommendations from CDC are available at http://www.cdc.gov/flu, as reported in the study by the Advisory Committee on Immunization Practices 1.
The highest quality study, based on recency and journal prestige, is the one published in 2011 in the Morbidity and Mortality Weekly Report 1, which provides the most up-to-date recommendations for the treatment of influenza.
From the Research
Possible Causes of Persistent Influenza
The possible causes of persistent influenza, also known as prolonged influenza or post-influenza complication, are not directly addressed in the provided studies. However, the studies suggest that influenza can cause significant morbidity and mortality in certain populations, such as young children, the elderly, pregnant and post-partum women, patients with co-morbidities, and the immunocompromised 2.
Factors Contributing to Prolonged Influenza
Some factors that may contribute to prolonged influenza include:
- Delayed treatment with antiviral drugs, such as oseltamivir, which can reduce the duration and severity of illness if initiated within 48 hours of symptom onset 3, 2, 4
- Inadequate vaccination, which can reduce the risk of influenza illness in healthy adults by 75%-80% 4
- Underlying chronic diseases, which can increase the risk of influenza-related complications 2, 4
- Immunocompromised status, which can increase the risk of influenza-related complications 2, 4
Complications of Influenza
Influenza can lead to various complications, including:
- Otitis media in children 2
- Lower respiratory tract complications, resulting in antibiotic therapy, in adults 2
- Pneumonia or hospitalization 5
- Influenza-related hospitalization 5
- All-cause hospitalization 5
Treatment and Prevention
Antiviral drugs, such as oseltamivir, zanamivir, and baloxavir marboxil, can modify the severity of illness and reduce the duration of illness by about 1.5-2.5 days 3, 2, 4, 6. Vaccination is also an effective way to prevent influenza, especially in high-risk populations 4.