Influenza

Key points

• Symptoms typically begin abruptly, within one to two days of exposure, and include fever, chills, aching muscles and a dry cough.
• Children more often experience vomiting and diarrhoea with the infection, whereas healthy adults typically clear the illness within a week or two.
• Oseltamivir works best started within 48 hours of symptoms, reducing illness duration by blocking the enzyme that lets the virus spread between cells.

Symptoms and when they strike

Flu tends to arrive abruptly. Fever above 38 C, chills, muscle aches, headache, and a dry cough typically appear within one to two days of exposure. Fatigue can be severe enough to keep people in bed for several days. Sore throat and a runny nose are common; vomiting and diarrhoea occur more often in children. Most otherwise healthy adults recover fully within one to two weeks.

Seek medical attention promptly if symptoms include difficulty breathing, chest pain, persistent high fever, confusion, or cyanosis, these can signal serious complications such as pneumonia.

Antiviral treatment

Antivirals work best when started early, ideally within 48 hours of the first symptoms. Oseltamivir (Tamiflu) is the most widely used option; it reduces the duration and severity of illness by inhibiting the neuraminidase enzyme that allows the virus to spread between cells. Rest, adequate fluids, and paracetamol or ibuprofen for fever and pain support recovery alongside antiviral therapy.

Further reading

• About Influenza | Influenza (Flu) - CDC
• Influenza (seasonal)
• Influenza
• Influenza (Disease Index) - NICD