How Many Influenza Viruses Are There

These pages includes information about the estimated burden of influenza from past seasons including tables of the estimated influenza disease burden and 95 credible interval cr i by age group. Many different combinations of ha and na proteins are possible. Since both diseases are viral antibiotics cannot conquer cold or flu.

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Understanding The Different Kinds Of Flu Viruses

Why Did The Flu Kill 80 000 Americans Last Year

Type d has not been known to infect humans but is believed to have the potential to do so.

How many influenza viruses are there. From september 29 2019 to april 4 2020. Interim estimates of 2019 2020 flu vaccine effectiveness have been released. Three of the four types of influenza viruses affect humans. A b c and d.

From september 29 2019. Antigenic characterization of influenza viruses antigens are molecular structures on the surface of viruses that are recognized by the immune system and are capable of triggering an immune response antibody production. A b and c. Type a and b cause the annual influenza epidemics that have up to 20 of the population sniffling aching coughing and running high fevers.

Influenza a viruses also are found in many different animals including ducks chickens pigs whales horses and seals. Usually the virus is spread through the air from coughs or sneezes especially in cold dry air. This is believed to occur mostly over relatively short distances. Influenza a viruses are the only influenza viruses known to cause flu pandemics i e global epidemics of flu disease.

Influenza d may also have the potential to do so if the potential for future transmission from animals to humans comes to fruition. Influenza virus characterization from viruses collected in the u s. Virus subtype or lineage. The virus particle also called the virion is 80 120 nanometers in diameter such that the smallest virions adopt an elliptical shape.

Cdc genetically characterized 2 463 influenza viruses collected in the u s. There are three types of flu viruses. Influenza type a viruses are very similar in structure to influenza viruses types b c and d. Type a type b and type c.

Three types of flu viruses a b and c cause seasonal influenza. More than 100 types of cold viruses are known and new strains of flu evolve every few years. There are four types of influenza viruses. There are 18 known ha subtypes and 11 known na subtypes.

For example an h7n2 virus. Subtypes of influenza a viruses. The length of each particle varies considerably owing to the fact that influenza is pleomorphic and can be in excess of many tens of micrometers producing. Hemagglutinin ha and neuraminidase na image icon.

Seasonal flu is the type of influenza that typically causes illness for just a few months out of the year. Information on how these estimates are calculated can be found on cdc s web page how cdc estimates the burden of seasonal influenza in the u s. Influenza a viruses are divided into subtypes on the basis of two proteins on the surface of the virus. Human influenza a and b viruses cause seasonal epidemics of disease known as the flu season almost every winter in the united states.