Skip to main content

Military Health System

Test of Sitewide Banner

This is a test of the sitewide banner capability. In the case of an emergency, site visitors would be able to visit the news page for addition information.

Influenza, Northern Hemisphere


Seasonal Influenza Vaccination Training: This course is currently being updated for the 2023-24 flu season. An announcement will be made on the Seasonal Influenza Resource Center and at https://health.mil/vaccines when it becomes available. When published, this course will meet the seasonal influenza vaccination training requirement for medical personnel administering influenza vaccinations.

In the meantime, there is influenza training available from the CDC’s You Call The Shots that will meet this requirement, even after the Continuing Education credit for this course expires in September 2023. If you have already completed the training, be sure to review the latest CDC recommendations, published on Aug. 25, 2023, to ensure currency. Upon completion of non-DOD training, be sure to print out your certificate of completion to ensure proper documentation with your unit or organization.


2023-2024 Seasonal Influenza Resource Center for Health Care Personnel

Flu disease picture  Influenza is a highly contagious viral infection. There are three main antigen types of influenza: types A, B, and C. Influenza type A causes moderate to severe illness and affects all age groups. Type A can infect both humans and animals. The notion that influenza type B generally causes milder disease than type A has been recently challenged and is more fatal in children. Type B mainly infects humans. Influenza type C only causes mild respiratory illness. Influenza activity peaks from December to March in the Northern Hemisphere.

Influenza is transmitted from person to person mainly when an infected person coughs or sneezes. Transmission can also occur from direct contact with respiratory secretions, such as when touching surfaces contaminated with influenza virus and then touching the eyes, nose, or mouth, or from indirect contact with droplets from coughs or sneezes. Transmission can occur from the day before symptoms begin until about 5 days after symptoms begin in adults, or up to 10 days or more after symptoms begin in children.

About 50% of infected persons will develop "classic" influenza disease. This is characterized by the abrupt onset of fever, muscle pain, sore throat, nonproductive cough, runny nose, and headache. These symptoms generally last from 2 to 3 days. However, some people may experience a loss of strength or energy for several weeks. In addition, some people may develop complications, such as pneumonia.

Source: Centers for Disease Control and Prevention

You also may be interested in...

Last Updated: August 25, 2023
Follow us on Instagram Follow us on LinkedIn Follow us on Facebook Follow us on Twitter Follow us on YouTube Sign up on GovDelivery