Can the flu lead to other illness?

Yes, the flu can lead to other illnesses. In some cases, the flu can lead to pneumonia, which is an infection of the lungs. Pneumonia can be a serious illness, especially for young children, the elderly, and people with weakened immune systems. In rare cases, the flu can also lead to encephalitis, which is an infection of the brain. Encephalitis can also be a serious illness and can lead to permanent disability or death.