Southern Hemisphere Influenza Vaccine Resource Center

Influenza is a world-wide highly contagious respiratory viral infection. There are four types of influenza virus: A, B, C, and D. Type A influenza viruses are the only known type to cause flu pandemics. Influenza B viruses generally cause milder disease and affects humans only. Influenza C is rarely reported as a cause of human illness and has not been associated with epidemic disease. Influenza D is not known to cause illness in humans. Annual epidemics of influenza typically occur between October - March in the Northern Hemisphere and April – September in the Southern Hemisphere.

Influenza is transmitted person to person via large droplets that are expelled when a person coughs or sneezes. These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs. Less often, a person might get flu by touching a surface or object that has flu virus on it and then touching their own mouth, nose, or possibly their eyes. Transmission can occur from the day before symptoms begin until about five days after symptoms begin in adults, or up to seven days or more after symptoms begin in children.

Classic symptoms of Influenza include abrupt onset of fever, cough, muscle pain, sore throat, runny nose, headache, and fatigue. These symptoms generally last from three to seven days, however some people may experience a cough or weakness for several weeks. In addition, some people may develop complications, such as bacterial pneumonia, sinus infections, and worsening of chronic medical conditions. Older adults, very young children, pregnant persons, immunocompromised individuals, and those with chronic medical conditions are particularly vulnerable to serious influenza related complications. Influenza season varies depending on geography. In the Southern Hemisphere, influenza flu activity typically occurs between April and September, and peaks in the winter months (June-August). The predominant influenza strains are constantly changing and often differ between NH and SH. Each year, the World Health Organization analyzes influenza data from both hemispheres to determine which strains are likely to circulate in these regions in their upcoming season.

Annual influenza vaccination is the best way to protect yourself from flu and is recommended for all persons aged ≥6 months without contraindications. There is only one SH Influenza vaccine available in the United States. SH vaccination is required for all active duty and select reserve personnel traveling between NH and SH for 14 days or more between April and September. Persons traveling to the Southern Hemisphere during the flu season should be vaccinated at least two weeks prior to entry into the region. The Northern and Southern Hemisphere Influenza vaccines should be separated by at least 30 days.

Source: DHA-PI 6025.52; Influenza (Flu) | CDC

Resource Center

You will find below all of the resources you will need for the Southern Hemisphere influenza season. More will be added as they are published or released.