Introduction
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Betainfluenzavirus
Influenza B virus
History
1940s
The Influenza B virus was first identified in 1940, differentiated from the already known Influenza A virus.1950s to 1970s
During this period, the Influenza B virus was considered a pathogen mainly affecting children and adolescents. Scientists began to include Influenza B virus strains in seasonal flu vaccines.1980s
Advances in molecular biology allowed researchers to conduct more in-depth genetic studies on the Influenza B virus, revealing patterns of mutation and evolution.1990s to 2000s
Global influenza surveillance systems were strengthened to track the evolution of Influenza B virus strains and to provide data support for the annual vaccine composition. The discovery of two major lineages of Influenza B virus (Victoria and Yamagata) led to the development of quadrivalent flu vaccines, including two strains of Influenza A and two strains of Influenza B.Early 21st century to present
Vaccine updates became more frequent to better match circulating strains. There was an enhancement in global cooperation, with the World Health Organization and national public health agencies working together to monitor flu strains, especially during widespread epidemics. New antiviral medications were developed as a deeper understanding of Influenza B virus biology emerged. Advancements in genome sequencing technologies have made rapid identification of virus strains possible, which is essential for monitoring mutations and formulating preventive measures.Genomic Structure
Influenza B virus, like all influenza viruses, has a segmented RNA genome. The genome of Influenza B virus consists of eight segments of single-stranded, negative-sense RNA, which together encode for 11 proteins.
| CDS | Function |
|---|---|
| PB1 (Polymerase Basic 1) | This segment encodes for the PB1 protein, which is a part of the viral RNA polymerase complex. It also encodes for the PB1-F2 protein through an alternative reading frame, which may contribute to virulence. |
| PB2 (Polymerase Basic 2) | Encodes for the PB2 protein, another component of the RNA polymerase complex, which is involved in recognizing the cap structure of host pre-mRNA for viral mRNA synthesis. |
| PA (Polymerase Acidic) | Encodes for the PA protein, also a part of the RNA polymerase complex. It also encodes for the PA-X protein via ribosomal frameshifting, which can modulate host cell protein synthesis. |
| HA (Hemagglutinin) | Encodes for hemagglutinin, a surface glycoprotein that allows the virus to bind to host cell receptors and initiate infection. It is also the primary antigen against which immune responses are directed. |
| NP (Nucleoprotein) | Encodes for the nucleoprotein, which encapsidates the viral RNA to form a ribonucleoprotein complex, important for the virus's structure and function. |
| NA (Neuraminidase) | This segment encodes for neuraminidase, another surface glycoprotein that facilitates the release of progeny virus from infected cells and the spread of infection. |
| M (Matrix) | Encodes for two proteins, M1 and M2. M1 (matrix protein) plays a role in virus assembly and budding, while M2 (an ion channel) is involved in viral entry and uncoating. |
| NS (Non-Structural) | Encodes for NS1, a multifunctional protein that antagonizes the host immune response, and NEP (also known as NS2), which is involved in the nuclear export of viral ribonucleoproteins. |
Epidemiological Study
1、Historical Epidemic Events
The Influenza B virus has not caused pandemics on the scale of the Influenza A virus in 1918, 1957, 1968, and 2009. However, Influenza B continues to circulate every flu season and has been the predominant strain in some seasons. For example, during the 2017-2018 flu season, Influenza B was more prevalent than Influenza A in certain regions.
2、Strain Variations
The circulation of Influenza B virus can be characterized by the activity of its two main lineages: Victoria and Yamagata. These lineages show different patterns of circulation in different years and regions. Monitoring of the lineages helps predict future trends in circulation and vaccine strain selection.
3、Disease Burden
Assessments of the burden of disease caused by Influenza B virus show that although the illness it causes is generally milder than Influenza A, the impact on children and the elderly is still significant. The rates of medical utilization, hospitalization, and absences from school and work due to Influenza B virus are important public health considerations.
4、Vaccination
Vaccination remains the primary method of preventing Influenza B virus infection. With the concurrent circulation of both Influenza B lineages, quadrivalent vaccines containing two strains of Influenza A and two strains of Influenza B have become the recommended type of vaccine.
5、Global Monitoring and Response
The World Health Organization (WHO) monitors changes in the flu virus annually and updates its recommendations for the composition of vaccines for the upcoming flu season based on this information. Moreover, the Global Influenza Surveillance and Response System (GISRS) also monitors flu activity globally to enable timely responses to flu epidemics.
6、Antiviral Treatment
Antiviral medications like Oseltamivir and Zanamivir have been proven effective in reducing symptoms and duration of illness for Influenza B virus infections.
Preventive Tips
Personal Hygiene
Frequently wash your hands, especially after touching public surfaces or interacting with others. Use soap and water or an alcohol-based hand sanitizer.Avoid Close Contact
Limit close contact with people who are sick, and if you are infected with the flu, stay home to reduce the risk of spreading it to others.Cough and Sneeze Etiquette
Cover your mouth and nose with a tissue when you cough or sneeze, then discard the tissue immediately and wash your hands. If no tissue is available, cough or sneeze into your bent elbow.Vaccination
Get the seasonal flu vaccine according to local public health guidelines, as the virus strains can change each season and immunity from vaccination diminishes over time.High-Risk Groups
Pay special attention to prevention in high-risk groups such as infants, the elderly, pregnant women, and individuals with chronic conditions like asthma, diabetes, or heart disease who may develop more severe complications from the flu.