Individuals whose immune systems are not fully developed (such as infants) or are weakened (such as the elderly) cannot generate such a lethal immune response. For WHO, the development of vaccines against animal influenza viruses, as well as seasonal influenza vaccines that induce broadly protective and long-lasting immune responses, are high priorities. Examples of influenza A subtypes include H1N1, H5N1, and H3N2. This same virus, H5N1, reappeared among chicken flocks in Southeast Asia during the winter of 2003–04, again infecting some people fatally, and it has reappeared periodically since, primarily in wild birds, domestic poultry, and humans. Antigen is the component of the flu vaccine that prompts your body’s immune response. A temporary hospital in Camp Funston, Kansas, during the 1918–19 influenza pandemic. Originally called swine flu because the virus was suspected to have been transmitted to humans from pigs, the illness first broke out in Mexico and then spread to the United States. Coronavirus disease outbreak (COVID-2019), Coronavirus disease outbreak (COVID-19) », Vaccines against influenza - English and French version (November 2012), Full list of WHO position papers and accompanying documents, WHO Influenza surveillance and monitoring, WHO Global Epidemiological Surveillance Standards for Influenza (July 2012), Searchable database of WHO prequalified vaccines (select disease as vaccine type), Guidelines for National Regulatory Authorities (NRAs) - recommendations and risk assessments, Strategic Advisory Group of Experts (SAGE) on Immunization working group on influenza vaccines and immunization, WHO Initiative for Vaccine Research (IVR) activities on influenza, Global Action Plan for Influenza Vaccines (GAP), WHO Avian Influenza website and resources, WHO Guidelines for Pharmacological Management of Pandemic Influenza A(H1N1) 2009 and other Influenza Viruses (Rev February 2010), Clinical management of human infection with avian influenza A (H5N1) virus, Clinical management of influenza pandemic (H1N1) 2009 and other acute respiratory illness in resource-limited settings, US Centers for Disease Control and Prevention (CDC) - seasonal influenza, US Centers for Disease Control and Prevention (CDC) - avian influenza, Public health England - seasonal influenza, European Centre for Disease Prevention and Control (ECDC) - influenza, Framework for decision-making: implementation of mass vaccination campaigns in the context of COVID-19, Immunization in the context of COVID-19 pandemic, Guiding principles for immunization activities during the COVID-19 pandemic: interim guidance, Read the interim recommendations for Ebola vaccines, Recommandations provisoires sur la vaccination contre la maladie à virus Ebola (MVE), Call for consultant: National Immunization Strategy (NIS). Influenza (Flu) Viruses There are two main types of influenza (flu) virus: Types A and B. It commonly occurs in epidemics, one of which killed 20 million people between 1917 and 1919. The influenza pandemic of 1918–19, the most destructive influenza outbreak in history and one of the most severe disease pandemics ever encountered, was caused by a subtype of influenza A known as H1N1. Get exclusive access to content from our 1768 First Edition with your subscription.

A viral infection that is much like a severe cold, but may also infect the throat and ears and can be fatal in the weak or elderly. The immune response to vaccination results in the development of protective antibodies against the viruses used to make the vaccine. In the United States the high levels of flu-like illness observed during the 2009 H1N1 pandemic were not observed again until 2018.

The influenza A and B viruses that routinely spread in people (human influenza viruses) are responsible for seasonal flu epidemics each year. Influenza D viruses are not known to infect humans and have been observed only in pigs and cattle. Subsequent pandemics of influenza have been less severe. (Pathology) a highly contagious and often epidemic viral disease characterized by fever, prostration, muscular aches and pains, and inflammation of the respiratory passages. On June 11, 2009, following an increase in cases in Chile, Australia, and the United Kingdom, WHO raised the H1N1 alert level from 5 to 6, meaning that the outbreak was officially declared a pandemic. Articles from Britannica Encyclopedias for elementary and high school students. noun Pathology. https://www.thefreedictionary.com/influenza. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox.