Influenzavirus C

Influenza C virus is the species in the genus Influenzavirus C, in the virus family Orthomyxoviridae, which like other influenza viruses, causes influenza. Influenza C viruses are known to infect humans and pigs. Flu due to the Type C species is rare compared to Types A or B, but can be severe and can cause local epidemics. Type C has 7 RNA segments and encodes 9 proteins, while Types A and B have 8 RNA segments and encode at least 10 proteins. Influenza viruses are members of the family Orthomyxoviridae. Influenza viruses A, B, C, and D represent the four antigenic types of influenza viruses. Of the four antigenic types, influenza A virus is the most severe, influenza B virus is less severe but can still cause outbreaks, and influenza C virus is usually only associated with minor symptoms. Influenza D virus is 50% similar in amino acid composition to influenza C virus, similar to the level of divergence between types A and B, while types C and D have a much greater level of divergence from types A and B. Influenzaviruses C and D were estimated to have diverged from a single ancestor over 1,500 years ago, around 482 AD. Influenza A virus can infect a variety of animals as well as humans, and its natural host or reservoir is birds, whereas influenza viruses B, C, and D do not have animal reservoirs.Influenza C virus is not as easily isolated so less information is known of this type, but studies show that it occurs worldwide. Influenza C virus currently has 6 lineages, which were estimated to have emerged around 1896 AD. This virus may be spread from person to person through respiratory droplets or by fomites (non-living material) due to its ability to survive on surfaces for short durations. Influenza viruses have a relatively short incubation period (lapse of time from exposure to pathogen to the appearance of symptoms) of 18–72 hours and infect the epithelial cells of the respiratory tract. Influenza virus C tends to cause mild upper respiratory infections. Cold-like symptoms are associated with the virus including fever (38-40ᵒC), dry cough, rhinorrhea (nasal discharge), headache, muscle pain, and achiness. The virus may lead to more severe infections such as bronchitis and pneumonia. After an individual becomes infected, the immune system develops antibodies against that infectious agent. This is the body's main source of protection. Most children between five and ten years old have already produced antibodies for influenza virus C. As with all influenza viruses, type C affects individuals of all ages, but is most severe in young children, the elderly and individuals with underlying health problems. Young children have less prior exposure and have not developed the antibodies and the elderly have less effective immune systems. Influenza virus infections have one of the highest preventable mortalities in many countries of the world.