From the Guidelines
Influenza A is a type of influenza virus that can cause significant clinical illness in a high proportion of those infected, and has the potential to emerge as a pandemic strain.
Characteristics of Influenza A
- Influenza A viruses are further classified into subtypes on the basis of their surface hemagglutinins (HA, H1–16) and neuraminidases (NA, N1–9) 1
- Antigenic drift and antigenic shift are two mechanisms by which influenza A viruses can change and evade existing humoral immunity, with antigenic shift often resulting in a pandemic 1
- Influenza A viruses can infect humans, spread efficiently from person to person, and cause significant clinical illness in a high proportion of those infected 1
Pandemic Potential
- Influenza A viruses have been responsible for several pandemics, including the 1918 "Spanish flu" pandemic, which killed between 20 and 40 million people worldwide 1
- The emergence of a new influenza A virus subtype with pandemic potential is unpredictable, but international concern has increased regarding the possibility that avian influenza A/H5N1 may evolve to produce the next pandemic 1
Clinical Significance
- Influenza A can cause significant morbidity and mortality, particularly in certain populations such as older adults, young children, and immunocompromised individuals, including solid organ transplant recipients 1
From the Research
Definition of Influenza A
- Influenza A is an infectious respiratory disease caused by influenza A viruses 2, 3, 4, 5, 6
- It is characterized by annual seasonal epidemics and sporadic pandemic outbreaks 2
- Influenza A virus is the primary causative agent of influenza, colloquially called the flu 3
Characteristics of Influenza A
- Influenza A virus can evolve from an animal infected pathogen to a human infected pathogen 4
- The virus can cause zoonotic infection with stable adaptation to human, leading to sustained horizontal transmission 4
- Influenza A virus is highly infectious and can result in significant morbidity and mortality worldwide 6
Impact of Influenza A
- Annual epidemics of influenza result in ~1 billion infections, 3–5 million cases of severe illness and 300,000–500,000 deaths 2
- The severity of pandemic influenza depends on multiple factors, including the virulence of the pandemic virus strain and the level of pre-existing immunity 2
- Influenza A virus can cause devastating avian outbreaks with worldwide losses worth billions of dollars 3
Detection and Treatment of Influenza A
- Various detection methods are available for Influenza A virus, including laboratory-based techniques and point-of-care strategies 5
- Rapid molecular assays are the preferred diagnostic tests because they can be done at the point of care, are highly accurate, and have fast results 6
- Treatment with anti-influenza drugs may be considered if the patient presents within 48 hours of symptom onset 6
- Annual influenza vaccination is recommended for all people six months and older who do not have contraindications 6