This phase can last 1 or 2 weeks. Individuals can remain infectious for up to 8 days after contracting the infection. The signs and symptoms of influenza are shown in Figure 2. Influenza signs and symptoms. Influenza is a serious infection in healthy adults and can be potentially fatal in those with underlying conditions.
Elderly sufferers are at a higher risk of complications.
In children, the clinical course is similar, but some aspects are more severe.