Influenza A virus (IAV) is the only species of the genus Alphainfluenzavirus of the virus family Orthomyxoviridae. It is a pathogen with strains that infect birds and some mammals, as well as causing seasonal flu in humans. Mammals in which different strains of IAV circulate with sustained transmission are bats, pigs, horses and dogs; other mammals can occasionally become infected.
Avian influenza, also known as avian flu or bird flu, is a disease caused by the influenza A virus, which primarily affects birds but can sometimes affect mammals including humans. Wild aquatic birds are the primary host of the influenza A virus, which is enzootic in many bird populations.
Orthomyxoviridae is a family of negative-sense RNA viruses. It includes seven genera: Alphainfluenzavirus, Betainfluenzavirus, Gammainfluenzavirus, Deltainfluenzavirus, Isavirus, Thogotovirus, and Quaranjavirus. The first four genera contain viruses that cause influenza in birds and mammals, including humans. Isaviruses infect salmon; the thogotoviruses are arboviruses, infecting vertebrates and invertebrates. The Quaranjaviruses are also arboviruses, infecting vertebrates (birds) and invertebrates (arthropods).
Influenza A virus subtype H5N1 (A/H5N1) is a subtype of the influenza A virus, which causes influenza (flu), predominantly in birds. It is enzootic in many bird populations, and also panzootic. A/H5N1 virus can also infect mammals that have been exposed to infected birds; in these cases, symptoms are frequently severe or fatal.
Swine influenza is an infection caused by any of several types of swine influenza viruses. Swine influenza virus (SIV) or swine-origin influenza virus (S-OIV) refers to any strain of the influenza family of viruses that is endemic in pigs. As of 2009, identified SIV strains include influenza C and the subtypes of influenza A known as H1N1, H1N2, H2N1, H3N1, H3N2, and H2N3.
Influenza A virus subtype H1N1 (A/H1N1) is a subtype of influenza A virus (IAV). Some human-adapted strains of H1N1 are endemic in humans and are one cause of seasonal influenza (flu). Other strains of H1N1 are endemic in pigs and in birds. Subtypes of IAV are defined by the combination of the antigenic H and N proteins in the viral envelope; for example, "H1N1" designates an IAV subtype that has a type-1 hemagglutinin (H) protein and a type-1 neuraminidase (N) protein.
Influenza A virus subtype H3N2 (A/H3N2) is a subtype of influenza A virus (IAV). Some human-adapted strains of A/H3N2 are endemic in humans and are one cause of seasonal influenza (flu). Other strains of H1N1 are endemic in pigs and in birds. Subtypes of IAV are defined by the combination of the antigenic H and N proteins in the viral envelope; for example, "H1N1" designates an IAV subtype that has a type-1 hemagglutinin (H) protein and a type-1 neuraminidase (N) protein.
An emergent virus is a virus that is either newly appeared, notably increasing in incidence/geographic range or has the potential to increase in the near future. Emergent viruses are a leading cause of emerging infectious diseases and raise public health challenges globally, given their potential to cause outbreaks of disease which can lead to epidemics and pandemics. As well as causing disease, emergent viruses can also have severe economic implications. Recent examples include the SARS-related coronaviruses, which have caused the 2002–2004 outbreak of SARS (SARS-CoV-1) and the 2019–2023 pandemic of COVID-19 (SARS-CoV-2). Other examples include the human immunodeficiency virus, which causes HIV/AIDS; the viruses responsible for Ebola; the H5N1 influenza virus responsible for avian influenza; and H1N1/09, which caused the 2009 swine flu pandemic. Viral emergence in humans is often a consequence of zoonosis, which involves a cross-species jump of a viral disease into humans from other animals. As zoonotic viruses exist in animal reservoirs, they are much more difficult to eradicate and can therefore establish persistent infections in human populations.
Treatments for influenza include a range of medications and therapies that are used in response to disease influenza. Treatments may either directly target the influenza virus itself; or instead they may just offer relief to symptoms of the disease, while the body's own immune system works to recover from infection.
The genetic structure of H5N1, a highly pathogenic avian influenza virus, is characterized by a segmented RNA genome consisting of eight gene segments that encode for various viral proteins essential for replication, host adaptation, and immune evasion.
Keshan disease is a congestive cardiomyopathy caused by a combination of dietary deficiency of selenium and the presence of a mutated strain of Coxsackievirus, named after Keshan County of Heilongjiang province, Northeast China, where symptoms were first noted. These symptoms were later found prevalent in a wide belt extending from northeast to southwest China, all due to selenium-deficient soil. The disease peaked in 1960–1970, killing thousands of people.
H5N1 influenza virus is a type of influenza A virus which mostly infects birds. H5N1 flu is a concern due to the its global spread that may constitute a pandemic threat. The yardstick for human mortality from H5N1 is the case-fatality rate (CFR); the ratio of the number of confirmed human deaths resulting from infection of H5N1 to the number of those confirmed cases of infection with the virus. For example, if there are 100 confirmed cases of a disease and 50 die as a consequence, then the CFR is 50%. The case fatality rate does not take into account cases of a disease which are unconfirmed or undiagnosed, perhaps because symptoms were mild and unremarkable or because of a lack of diagnostic facilities. The Infection Fatality Rate (IFR) is adjusted to allow for undiagnosed cases.
Influenza, commonly known as the flu, is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms begin one to four days after exposure to the virus and last for about two to eight days. Diarrhea and vomiting can occur, particularly in children. Influenza may progress to pneumonia from the virus or a subsequent bacterial infection. Other complications include acute respiratory distress syndrome, meningitis, encephalitis, and worsening of pre-existing health problems such as asthma and cardiovascular disease.
An inactivated vaccine is a type of vaccine that contains pathogens that have been killed or rendered inactive, so they cannot replicate or cause disease. In contrast, live vaccines use pathogens that are still alive. Pathogens for inactivated vaccines are grown under controlled conditions and are killed as a means to reduce infectivity and thus prevent infection from the vaccine.
The pandemic H1N1/09 virus is a swine origin influenza A virus subtype H1N1 strain that was responsible for the 2009 swine flu pandemic. This strain is often called swine flu by the public media due to the prevailing belief that it originated in pigs. The virus is believed to have originated around September 2008 in central Mexico.
Elodie Ghedin is a Canadian parasitologist and virologist as well as a professor at the New York University Center for Genomics and Systems Biology. Her work focuses on the molecular biology and genomics of the parasites that cause diseases such as elephantiasis, and river blindness, and on the evolution of the influenza virus. She was named a 2011 MacArthur Fellow, a 2012 Kavli Frontier of Science Fellow, and a 2017 American Academy of Microbiology Fellow. She also was Awarded the Chancellor’s Distinguished Research Award in 2010.
A H5N1 vaccine is an influenza vaccine intended to provide immunization to influenza A virus subtype H5N1.
Wendy Sue Fox is a British virologist. She is currently head of Department of Infectious Disease and chair in Influenza Virology at Imperial College London. She leads a team of scientists studying the influenza virus and its physiology and morphology to discover novel vaccines. In particular, they are trying to understand more about influenza virus mutations, and how they can allow scientists to create new vaccines against possible flu pandemics.
A nasal vaccine is a vaccine administered through the nose that stimulates an immune response without an injection. It induces immunity through the inner surface of the nose, a surface that naturally comes in contact with many airborne microbes. Nasal vaccines are emerging as an alternative to injectable vaccines because they do not use needles and can be introduced through the mucosal route. Nasal vaccines can be delivered through nasal sprays to prevent respiratory infections, such as influenza.
Allison Elizabeth Aiello is an American epidemiologist. She is a professor of Epidemiology and a Carolina Population Center Fellow at the University of North Carolina at Chapel Hill. Aiello is an expert in influenza, investigating non-pharmaceutical interventions for flu prevention.
