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[Influenza--the last big epidemic. What makes it so dangerous?]
1Robert-Koch-Institut, Berlin.
Abstract:
In Germany, influenza lays low millions--and causes up to 15,000 deaths--every year. Three factors in particular are responsible for the severity of the disease: the cytocidal action of the virus--which, via hematogeneous spread, can involve not only the respiratory tract but also other organs such as the heart--, the immune response with fever and the production of pro-inflammatory cytokines, and bacterial superinfection of the virally predamaged respiratory mucosa. A particular threat is posed by influenza pandemics, which are usually associated with extremely high mortality and morbidity rates. The development of pandemics is furthered by the potential of the viral genome to undergo a so-called shift, as a result of which a reservoir of, for example, avian influenza A viruses can give rise to subtypes that are a danger to humans, and against which there is initially no protection. While the deaths caused by an epidemic are to be seen largely among old and multimorbid people, a pandemic also endangers the health and life of young and healthy persons.
Insights
Influenza causes millions of illnesses and up to 15,000 deaths annually in Germany. Pandemics, driven by viral genetic shifts, pose a severe threat to all age groups, including healthy individuals.
Area of Science:
- Virology and immunology
- Epidemiology of infectious diseases
Context:
- Annual influenza epidemics in Germany cause significant morbidity and mortality.
- Influenza virus has cytocidal effects, impacting the respiratory tract and other organs.
- Bacterial superinfections complicate viral respiratory damage.
Purpose:
- To elucidate the multifactorial determinants of influenza severity in Germany.
- To highlight the specific risks associated with influenza pandemics.
- To explain the mechanisms driving pandemic emergence and their public health implications.
Summary:
- Influenza severity stems from viral cytopathic effects, host immune responses (fever, cytokines), and secondary bacterial infections.
- Influenza pandemics, characterized by high mortality and morbidity, arise from viral genome reassortment (shift).
- Pandemics can emerge from zoonotic reservoirs (e.g., avian influenza A), creating novel strains against which humans lack immunity.
- Unlike seasonal epidemics primarily affecting the elderly and comorbid, pandemics endanger younger, healthier populations.
Impact:
- Understanding these factors is crucial for developing effective public health strategies against influenza.
- The potential for rapid pandemic development necessitates ongoing surveillance and preparedness.
- This research underscores the need for protective measures against both seasonal flu and novel pandemic strains.