Richard A. Stein, MD, PhD
A new H1N1 triple-reassortant â€œswineâ€ influenza virus was recently described in individuals from the United States and Mexico who presented with respiratory symptoms, and the same virus was subsequently confirmed in patients from several countries around the world. The circumstances surrounding the emergence of this pathogen, and the factors that facilitated the initial cross-species transmission, are still incompletely understood. It became apparent in the early days of the outbreak that the virus can be directly transmitted between humans. Pathogens that originate in animal reservoirs and subsequently acquire the potential for human-to-human transmission have caused outbreaks throughout human history. Although each outbreak is marked by its own particularities, it is important to remember the teachings that emerge from previous epidemics and pandemics. Integrating the important lessons of the past will provide the best opportunity to understand hostâ€“pathogen interaction and the most powerful approach to implementing effective prophylactic and therapeutic measures.
The influenza virus single-stranded RNA genome is organized into 8 segments. In a process known as reassortment, 2 or more viruses that co-infect the same cell can exchange 1 or more RNA segments to generate strains with new antigenic properties and new biological characteristics. During the 1957 “Asian influenza” pandemic, 3 genes from an avian H2N2 virus were introduced into a human H1N1 strain and created a new virus with pandemic capabilities. This exchange of genetic material probably occurred during the dual infection of a human or an animal, possibly a pig, with both viral strains. Derived from reference 25.
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Stein RA. Lessons From Outbreaks of H1N1 Influenza. Ann Intern Med. ;151:59–62. doi: 10.7326/0003-4819-151-1-200907070-00123
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Published: Ann Intern Med. 2009;151(1):59-62.
Infectious Disease, Influenza.
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Print ISSN: 0003-4819 | Online ISSN: 1539-3704
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