There are three types of influenza that affect individuals, healthcare providers, schools and businesses. (WHO Influenza Virus Infections in Humans (February 2014) – pulled January 2018)
Seasonal influenza viruses circulate and cause disease in humans every year. In temperate climates, disease tends to occur seasonally in the winter months, spreading from person-to-person through sneezing, coughing, or touching contaminated surfaces. Seasonal influenza viruses can cause mild to severe illness and even death, particularly in some high-risk individuals. Persons at increased risk include pregnant women, the very young and very old, immune-compromised people, and people with chronic underlying medical conditions.
Seasonal influenza strains can be the same viruses that were involved in pandemic influenza – such is the case with the H1N1 strain that caused the 2009 influenza pandemic.
A pandemic occurs when an influenza virus which was NOT previously circulating among humans emerges and transmits among humans.
Because most people do not have immunity, the viruses can circulate and cause large outbreaks outside of the normal influenza season.
The most recent pandemic was the H1N1 pandemic in 2009.
Humans can also be infected with influenza viruses that are routinely circulating in animals, such as avian influenza or swine influenza. All of these animal viruses are distinct from human influenza viruses and do not transmit easily between humans. Some may occasionally infect humans, however, and may cause disease ranging from mild conjunctivitis to severe pneumonia and even death.
Usually these human infections of zoonotic influenza are acquired through direct contact with infected animals or contaminated environments, and do not spread very far among humans.
General Information (for individuals, schools and businesses)
Influenza Resources for the Healthcare Industry
Other Occupational Use Resources