Flu virus type a and b
Pro Research Analysisby 
Searched over 200M research papers
Influenza Virus Types A and B: A Comparative Analysis
Overview of Influenza Virus Types A and B
Influenza viruses are highly variable RNA viruses belonging to the Orthomyxoviridae family, with three main types: A, B, and C. However, only types A and B are significant human pathogens5. These viruses are known for their ability to change their genetic makeup, which complicates efforts to control and prevent influenza outbreaks2.
Genetic Variability and Reassortment
Influenza A viruses are particularly known for their genetic variability, which arises from mechanisms such as gene recombination, deletions, insertions, and point mutations. This genetic flexibility allows for the emergence of new strains that can evade the immune system2. In contrast, influenza B viruses exhibit less genetic variability, and the mechanisms behind their genetic changes are not as well understood2.
Interestingly, while both influenza A and B viruses can reassort within their types, they do not form reassortants between types. This lack of intertypic reassortment is attributed to incompatibilities in the viral packaging signals and polymerase components, which prevent the incorporation of heterotypic segments into budding virions6 7 9 10.
Detection and Diagnosis
The detection rates of influenza A and B viruses vary significantly across different age groups and settings. For instance, influenza B is more commonly detected in children than in non-elderly adults, and its detection rate among the elderly is generally lower1. Rapid diagnostic tests, such as the Directigen FluA+B test, have shown high sensitivity and specificity for both types, although fresh specimens are recommended for accurate detection of influenza B4.
Clinical Characteristics
Despite the genetic differences, the clinical presentations of influenza A and B infections are remarkably similar. Studies have shown that the signs and symptoms of influenza are largely indistinguishable between the two types, regardless of the patient's age or the specific virus subtype3. This similarity in clinical presentation underscores the importance of laboratory confirmation for accurate diagnosis and treatment.
Epidemiology and Public Health Implications
Influenza B viruses are a significant cause of morbidity, particularly in children aged 1 to 10 years. In the Asia-Pacific region, influenza B has been associated with a wide range of laboratory-confirmed influenza cases, varying from 0% to 92% in different seasons8. The co-circulation of both B lineages (Yamagata and Victoria) and frequent mismatches between vaccine strains and circulating strains highlight the need for quadrivalent vaccines to provide broader protection8.
Conclusion
Influenza A and B viruses, while sharing many clinical characteristics, differ significantly in their genetic variability and mechanisms of reassortment. The limited genetic variability of influenza B and the lack of intertypic reassortment with influenza A are key factors in their epidemiology and impact on public health. Accurate detection and appropriate vaccination strategies are essential for managing the burden of both types of influenza.
Sources and full results
Most relevant research papers on this topic
Heterogeneous estimates of influenza virus types A and B in the elderly: Results of a meta‐regression analysis
Influenza virus type B has a relatively low detection rate in older adults, especially in settings covering both inpatients and outpatients.
Meta-AnalysisVariation of influenza A, B, and C viruses.
Influenza A viruses show high variation in their genes, with recombination, deletions, and insertions, while type B and C viruses show lesser variation and less well-characterized mechanisms.
Highly CitedClinical Characteristics Are Similar across Type A and B Influenza Virus Infections
Despite differences in age distribution, the clinical illness produced by different influenza virus types and subtypes is indistinguishable among patients consulted by general practitioners for acute respiratory infections.
Observational Study
Rigorous JournalHighly CitedEvaluation of the Directigen FluA+B Test for Rapid Diagnosis of Influenza Virus Type A and B Infections
Directigen FluA+B is a highly sensitive and specific rapid test for detecting influenza virus types A and B, with potential applications in public health and clinical settings.
Observational StudyHighly CitedInfluenza: Propagation, Quantification, and Storage
Influenza viruses can be propagated, quantified, and stored in various media, depending on the clinical information and host of origin.
Highly CitedAn influenza A virus containing influenza B virus 5' and 3' noncoding regions on the neuraminidase gene is attenuated in mice.
This study successfully created a chimeric influenza A/B virus that is attenuated in mice and shows potential for a live attenuated virus vaccine.
In Vitro StudyHighly CitedInfluenza A and B Virus Intertypic Reassortment through Compatible Viral Packaging Signals
The lack of influenza A and B virus reassortants is partially due to incompatibilities in virus-specific packaging signals, which hinder segment incorporation into nascent virions.
In Vitro StudyHighly CitedLiterature review of the epidemiology of influenza B disease in 15 countries in the Asia‐Pacific region
A shift from trivalent to quadrivalent seasonal influenza vaccines could provide broader protection against influenza B in the Asia-Pacific region, where mismatches between circulating lineages and vaccine strains are common.
Systematic ReviewLimited compatibility between the RNA polymerase components of influenza virus type A and B.
Limited compatibility among RNA polymerase components of influenza virus types A and B suggests that incompatibility among these components is not solely responsible for the lack of heterotypic reassortants.
In Vitro StudyIdentification of a Type-Specific Promoter Element That Differentiates between Influenza A and B Viruses
The nucleotide at position 5 in the 3′ end of influenza A and B viruses' vRNA promoters is a critical type-specific determinant, playing a key role in modulating polymerase activity and contributing to their RNP incompatibility.
In Vitro Study