2024年9月18日 · There are four types of influenza viruses: A, B, C, and D. Influenza A and B viruses cause seasonal epidemics of disease in people (known as flu season) almost every winter in the United States. Influenza A viruses are the only influenza viruses known to cause flu pandemics (i.e., global epidemics of flu disease).

2025年1月23日 · Three types of flu viruses affect humans: types 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...

2024年9月11日 · There are four types of influenza (flu) viruses: A, B, C, and D. Influenza A and B viruses cause seasonal flu illness every fall and winter. Influenza A viruses are divided into subtypes based on the two proteins on the surface of the virus: hemagglutinin (H) and neuraminidase (N).

2023年10月3日 · There are 4 types of influenza viruses, types A, B, C and D. Influenza A and B viruses circulate and cause seasonal epidemics of disease. Influenza A viruses are further classified into subtypes according to the combinations of the proteins on the surface of the virus.

2023年1月23日 · There are four types of influenza viruses, A, B, C, and D. Influenza types A and B cause human infection annually during the epidemic season. Influenza A has several subtypes according to the combination of hemagglutinin (H) and the neuraminidase (N) proteins that are expressed on the surface of the viruses.

As of 30 January 2025 - 0530UTC, 159 countries shared 71,408 A/H1N1 genome sequences from sample collection in the last 5 years to making these data publicly accessible via GISAID EpiFlu. Circle size proportional to number of variant genomes, zoom into region for more detail. Color by recency with red being most recent.

1. The Influenza Virus and Subtypes. The influenza virus is an enveloped virus belonging to the Orthomyxoviridae family. There are four genera of influenza virus that infect vertebrates: influenza virus A, B, C, and D which are distinguished based on antigen differences in their matrix protein and nucleoprotein.

2010年5月13日 · Based on their main antigenic determinants, the haemagglutinin (H or HA) and neuraminidase (N or NA) transmembrane glycoproteins, influenza A viruses are further subdivided into 18 H (H1–H18) and 11 N (N1–N11) subtypes. Influenza A subtypes and B viruses are further classified by strains.

2025年1月16日 · In light of the ongoing avian influenza A (H5) virus animal outbreak in the United States, CDC now recommends subtyping of all influenza A virus-positive specimens from hospitalized patients on an accelerated basis.

Influenza is a single-stranded, helically shaped, RNA virus of the orthomyxovirus family. Three types of influenza virus are known to affect humans: A, B, and C. Type A influenza has subtypes determined by the surface antigens hemagglutinin (HA) and neuraminidase (NA). There are 18 different H subtypes and 11 different N subtypes.