Flu Information/Resources
How Flu Spreads
Person to Person
The main way that influenza viruses are spread is from person to person in respiratory droplets of coughs and sneezes. (This is called "droplet spread.") This can happen when droplets from a cough or sneeze of an infected person are propelled through the air and deposited on the mouth or nose of people nearby. Influenza viruses may also be spread when a person touches respiratory droplets on another person or an object and then touches their own mouth or nose (or someone else’s mouth or nose) before washing their hands.
The Flu Is Contagious
Most healthy adults may be able to infect others beginning 1 day before symptoms develop and up to 5 days after becoming sick. Children may pass the virus for longer than seven days. Symptoms start one to four days after the virus enters the body. That means that you may be able to pass on the flu to someone else before you know you are sick, as well as while you are sick. Some persons can be infected with the flu virus but have no symptoms. During this time, those persons can still spread the virus to others.
In the Northern hemisphere, winter is the time for flu. The timing and duration of flu seasons vary. While flu outbreaks can happen as early as October, most of the time influenza activity peaks in January or later. During the past 26 flu seasons, months with the heaviest flu activity (peak months) occurred in November one season, December four seasons, January five seasons, February 12 seasons, and March four seasons.
Monitoring Flu Activity
CDC collects, compiles and analyzes information on influenza activity year round in the United States and produces a weekly report from October through mid-May. The U.S. influenza surveillance system is a collaborative effort between CDC and its many partners in state and local health departments, public health and clinical laboratories, vital statistics offices, physicians, clinics and emergency departments, and the Departments of Defense and Veteran’s Affairs. Information in five categories is collected from 10 different data sources that allow CDC to:
- Find out when and where influenza activity is occurring
- Track influenza-related illness
- Determine what influenza viruses are circulating
- Detect changes in influenza viruses
- Measure the impact influenza is having on deaths in the United States
For more information about flu surveillance or to access the reports, visit Flu Activity & Surveillance
Source of above information or to learn more visit www.flu.gov
