From the Guidelines
Difference between Influenza A and Influenza B
Influenza A and Influenza B are distinct types of influenza viruses that cause epidemic human disease, with Influenza A being further categorized into subtypes based on two surface antigens: hemagglutinin (HA) and neuraminidase (NA), whereas Influenza B is not categorized into subtypes.
- The main difference between the two lies in their antigenic characteristics and the rate of antigenic drift, with Influenza A undergoing antigenic drift more rapidly than Influenza B 1.
- Influenza A viruses have the potential to cause pandemics due to antigenic shifts, which result in new or substantially different influenza A virus subtypes with little or no pre-existing immunity among humans 1.
- Influenza B viruses, on the other hand, are separated into two distinct genetic lineages, Yamagata and Victoria, but do not undergo antigenic drift as rapidly as Influenza A viruses 1.
- Both types of influenza viruses can cause significant illness, but the immunity to one type or subtype does not confer protection against another type or subtype, highlighting the importance of annual vaccination 1.
- The frequent emergence of antigenic variants through antigenic drift is the virologic basis for seasonal epidemics, necessitating the incorporation of new strains in each year's influenza vaccine 1.
From the Research
Differences between Influenza A and Influenza B
- Influenza A and B are two types of influenza viruses that can cause respiratory illness in humans 2, 3, 4, 5, 6
- Some studies suggest that Influenza A is more severe than Influenza B, with higher rates of pneumonia, mechanical ventilation, and in-hospital mortality 4, 5
- However, other studies have found no significant differences in clinical outcomes between Influenza A and B, including length of hospital stay, readmissions, and 30-day mortality 2, 3, 6
- Influenza B is often perceived as a less severe strain of influenza, but it can still cause significant morbidity and mortality, particularly in younger patients 2, 3
Demographic Differences
- Influenza A patients are often older than Influenza B patients, with a higher proportion of smokers and those with chronic obstructive pulmonary disease (COPD) and ischaemic heart disease (IHD) 2
- Influenza B patients are more likely to have underlying chronic kidney disease and present with vomiting on admission 4
- In children, there are no significant differences in clinical features or outcomes between Influenza A and B infections, regardless of age group 6
Clinical Outcomes
- Both Influenza A and B can cause severe illness, including pneumonia, acute coronary syndrome (ACS), and septic shock 2, 3, 4, 5
- The rate of clinical improvement is higher in Influenza B patients than in Influenza A patients, with a shorter length of hospital stay and lower in-hospital mortality 5
- However, other studies have found no significant differences in clinical outcomes between Influenza A and B, including length of hospital stay, readmissions, and 30-day mortality 2, 3, 6