What should you know about influenza A infectious period?

Influenza A spreads mainly through respiratory particles released when an infected person coughs, sneezes, talks or breathes. People may pass it on before they recognise the illness, with infectiousness often greatest around the start of symptoms. Children and people with weakened immune systems may remain contagious for longer.

Fever, chills, cough, headache, fatigue and feeling generally unwell can occur, but symptoms alone do not show exactly when transmission has ended. A lingering cough may remain after the highest-risk period, so ventilation and hand hygiene still help.

Stay home and avoid close contact while feverish or too unwell for normal activities. Improve ventilation, cover coughs and sneezes, wash hands, and consider a well-fitting mask when contact cannot be avoided. Do not share cups, towels or utensils. Take extra care around infants, older adults, pregnant people and anyone with a long-term condition.

Seek urgent care for severe breathing difficulty, chest pain, confusion, fainting, blue lips or severe dehydration. Contact a clinician if symptoms worsen after initial improvement, fever persists, or breathing becomes harder, because pneumonia can complicate influenza.

When can I safely return to work or school? Should household contacts take extra precautions? Would testing or antiviral treatment help? How should I protect someone at higher risk? Which symptoms mean I need urgent review?