Final answer:
The epidemiology of influenza involves studying the patterns of influenza outbreaks, which are more common in winter, particularly in the northern hemisphere.
Step-by-step explanation:
The epidemiology of influenza refers to the study of the patterns, causes, and effects of health and disease conditions in defined populations. It is a concern during specific times of the year, particularly in the winter months of the northern hemisphere when incidence patterns of influenza typically rise. Epidemics of influenza occur when there is a larger than anticipated number of cases in a short time frame within a geographical area.
Influenza is caused by the influenza virus and results in widespread illness and significant mortality rates annually. The threat of influenza is heightened by the virus's capacity to mutate through antigenic drift and shift, making it challenging to control and prevent. Pandemics, which are worldwide epidemics, can occur when new influenza virus strains emerge, such as the H7N9 strain in China during 2013. This particular strain had a high mortality rate and potential for becoming more communicable but did not result in a global pandemic.
Influenza is known for its severe impacts, including high rates of hospitalizations and deaths each season. Measures such as vaccination are crucial, with two new vaccines developed annually to combat the rapidly mutating virus. Surveillance by organizations like the World Health Organization and the Centers for Disease Control and Prevention is essential to monitor for outbreaks and prevent potential pandemics.