Latest data 1.1.
Influenza is one of the infectious diseases that peak during winter.
It peaks at different times in different winters. It is not possible to predict when it will peak, the size of the peak, which age groups will be most affected, or which strains will be the commonest. Influenza viruses infect the respiratory tract, and causes symptoms including a cold, cough and sore throat but also systemic symptoms of fever, headache, runny sore eyes and aching muscles. Some other viruses cause these symptoms, and laboratory tests are required to determine the cause. Patients who have systemic symptoms as well as a cold and a cough are, therefore, described as having flu or flu-like illness.