Influenza is an acute respiratory infectious disease caused by the influenza virus, with symptoms that typically appear suddenly and progress rapidly. Patients may develop noticeable symptoms within 1 to 4 days after exposure to the virus, with severity varying among individuals. Recognizing the characteristic symptoms helps in early diagnosis and treatment, reducing the risk of complications.
The manifestation of symptoms varies depending on age, immune system strength, and viral strain. Children may primarily experience fever and muscle aches, while elderly individuals or those with chronic illnesses may develop more severe respiratory problems. Early recognition of symptom changes and monitoring their severity are important for deciding when to seek medical care.
The early symptoms of influenza usually include systemic discomfort and localized respiratory symptoms. Patients often feel sudden fatigue, which may appear 12 to 24 hours before fever onset. Additionally, sore throat, mild nasal congestion, or sneezing are obvious signs that the virus has begun infecting the respiratory mucosa.
It is noteworthy that some patients may initially mistake these symptoms for a common cold, but influenza symptoms tend to worsen rapidly within 24 hours, which is markedly different from the gradual development of a common cold.
Peak symptoms typically occur on the 2nd to 3rd day after onset, mainly involving systemic and localized respiratory symptoms. Systemic symptoms such as high fever (often exceeding 38.5°C) can last several days and are accompanied by severe muscle soreness, especially in the lower limbs and back muscles. Respiratory symptoms include dry cough, chest tightness, and difficulty breathing, which may impair daily activities in severe cases.
Some patients may experience gastrointestinal symptoms such as loss of appetite, diarrhea, or nausea, which are more common in children. The combination of systemic and localized symptoms contrasts sharply with the localized upper respiratory symptoms of a common cold.
Symptoms usually peak within 3 to 7 days after onset and then gradually resolve. However, if symptoms do not improve after the 5th day or if secondary fever occurs, it may indicate bacterial superinfection or viral pneumonia. Cough may persist for more than two weeks, related to residual viral presence or airway tissue repair processes.
On days 3 to 4 after onset, patients may experience persistent high fever, altered consciousness, or rapid breathing, which are critical symptoms. Close monitoring of oxygen saturation and urine output is necessary to assess dehydration and organ load. Some patients may develop metabolic disturbances such as nausea and vomiting due to metabolic imbalance.
The resolution process usually involves a decrease in body temperature and reduced cough frequency, but some patients may experience recurrent low-grade fever during recovery, possibly related to immune system clearance of the virus and tissue repair.
If any of the following conditions occur, immediate medical attention should be sought: persistent high fever over 39°C for more than 48 hours, altered consciousness or disorientation, difficulty breathing with cyanosis of lips. These symptoms may indicate severe complications such as influenza-associated pneumonia, encephalitis, or metabolic acidosis.
Older adults over 65, pregnant women, and patients with chronic illnesses should consider it an emergency if mild symptoms worsen, such as well-controlled diabetic patients experiencing abnormal blood sugar levels, or heart disease patients with worsening chest pain. Children exhibiting seizures, inability to eat, or skin mottling (marbled skin) may indicate severe dehydration or metabolic crisis.
Even if symptoms seem mild, if you have had contact with a confirmed case and develop flu-like symptoms, active testing such as rapid antigen tests or PCR should be performed to block transmission. Antiviral medications provided by healthcare facilities, if used within 48 hours of symptom onset, can significantly shorten the course of illness and reduce the risk of complications.
Influenza symptoms usually appear suddenly and are more severe, including high fever (above 39°C), systemic muscle soreness, and extreme fatigue. Common colds mainly involve nasal congestion, runny nose, and mild sore throat. If accompanied by severe headache or persistent cough, prompt medical consultation is recommended to confirm if it is influenza.
Why can I still get infected despite receiving the flu vaccine?The effectiveness of the vaccine depends on the match between the vaccine strains and circulating viruses, as well as individual immune response. Each year's vaccine includes predicted prevalent strains based on the previous year's trends. Variations in circulating strains can reduce protection. Even if infected, vaccination can still lessen symptom severity and lower complication risks.
Why should I avoid excessive use of antipyretic drugs during fever?Overuse of antipyretics may burden the liver and kidneys and can mask the true progression of the illness. It is recommended to follow medical advice regarding dosage and prioritize physical cooling methods such as lukewarm sponge baths. Fever is a natural immune response to fight the virus and should not be suppressed abruptly in the short term.
Is a persistent cough during recovery from influenza normal? How should I handle it?A dry or productive cough during recovery is common, as the virus may damage the respiratory mucosa, and recovery may take 1 to 2 weeks. Consuming warm fluids like pear soup or honey water can soothe the throat. Avoid irritants such as smoke. If coughing up blood or high fever recurs, seek medical attention immediately.
Can I take Chinese and Western medicines simultaneously during influenza treatment?It is advisable to consult a healthcare professional before combining medications. Some herbal components may interact with antiviral drugs (such as oseltamivir), affecting efficacy or increasing side effects. Self-medicating without professional guidance may increase liver burden; medication adjustments should be made under medical supervision.
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