According to Doctor Nguyen Hoang Anh, a specialist I in the Infectious Diseases Unit, General Internal Medicine Department, Tam Anh General Hospital, TP HCM, flu typically causes fever, cough, body aches, and often resolves on its own after about one week. However, certain signs of worsening illness can signal dangerous complications, necessitating hospitalization.

Shortness of breath

Shortness of breath is a critical sign of severe flu progression. Patients may feel breathless when walking, climbing stairs, talking, or even at rest. Some individuals experience rapid, labored breathing, cannot lie down comfortably, or have bluish lips due to lack of oxygen. This condition can relate to flu virus pneumonia, bacterial superinfection, or acute lung injury, which reduces oxygen exchange capacity. Without timely detection and management, patients risk developing respiratory failure.

Persistent chest pain or tightness

Persistent chest pain, a feeling of pressure, or continuous tightness during a flu infection can signal complications in the lungs or cardiovascular system. Pneumonia often causes increased pain with deep breaths or coughing. Additionally, flu can trigger or worsen certain cardiovascular diseases, even causing myocarditis in some cases. Patients should not ignore chest pain accompanied by shortness of breath, sweating, dizziness, or an abnormal heart rhythm. Severe, prolonged, or sudden chest pain requires emergency medical attention to determine the cause, rather than self-medicating or waiting for symptoms to resolve.

Doctor Hoang Anh consulting a patient during a health check-up. Photo: Tam Anh General Hospital.

Confusion, persistent dizziness, or difficulty waking up

Severe flu impacts the entire body, especially with oxygen deficiency, severe dehydration, serious infection, or neurological complications. Patients may become disoriented, have slow reactions, lose their sense of direction, experience confusion, or be difficult to awaken. In elderly individuals, severe symptoms are sometimes atypical. Patients may suddenly become weaker, less alert, eat poorly, or exhibit behavioral changes instead of a distinct high fever.

Fever and cough decrease then suddenly worsen again

After several days of flu, fever and body aches typically subside. However, if a patient shows signs of recovery then experiences a return of fever, worsening cough, increased phlegm, or shortness of breath, they should be wary of complications such as secondary bacterial pneumonia. The flu virus damages the respiratory tract's protective barrier, creating conditions for pathogenic bacteria to invade. Post-flu bacterial pneumonia can progress rapidly, particularly in elderly individuals, those with man tinh illnesses, or immunocompromised individuals.

Reduced urination, extreme weakness, or inability to perform normal activities

Prolonged fever, poor appetite, and dehydration can lead to reduced urination, dizziness upon standing, exhaustion, or weakness to the point of unsteady walking in flu patients. These are also signs requiring attention, especially if the patient cannot drink enough fluids or has underlying heart or kidney conditions. Very little or no urination and marked weakness can indicate severe dehydration, circulatory failure, or systemic complications. If a patient cannot drink on their own, continuously vomits, faints, or shows signs of confusion, they require emergency care.

According to Doctor Hoang Anh, most flu patients can recover without hospitalization. However, individuals 65 years and older, pregnant women, and those with cardiovascular disease, man tinh lung disease, diabetes, kidney disease, or compromised immune systems face a higher risk of severe progression. These groups should seek medical attention immediately upon flu symptom onset for assessment and consideration of appropriate antiviral treatment.

Doctors will assess the degree of oxygen deficiency, lung damage, circulatory status, and complications to determine if hospitalization is necessary. Early antiviral treatment can help reduce the risk of complications in high-risk or severely ill individuals.

Nhat Thanh