H7N9 has unusual traits that could lead to a pandemic
David Morens, Jeffrey Taubenberger and Anthony Fauci from the U.S. National Institute of Allergy and Infectious Diseases described the history of H7 viruses and found that H7 influenza is inclined to become established in swine, horse and bird populations. As a result, the H7N9 virus could repeatedly be transmitted to humans.
"The evidence as a whole is complex and the implications of past outbreaks for predicting the future course of the current H7N9 epizootic (an epidemic among animals) are uncertain," the authors said.
The authors pointed out that H7 viruses were repeatedly involved in poultry outbreaks, such as incidents in the Netherlands, Mexico, Canada, Italy and New York. In nearly all the incidents, the viruses were eventually transmitted to humans. The viruses are also able to mutate from a low pathogenicity form to a high pathogenicity form in birds, which could result in large-scale culling and human exposure among poultry workers.
H7N9 also shares characteristics with highly pathogenic avian influenza H5N1, such as acute respiratory distress syndrome, bilateral pneumonia and multi-organ failure. H7 viruses also tend to infect conjunctivital cells, resulting in prominent signs and symptoms in the eyes and enhanced person-to-person spread in a H7N9 outbreak. The authors also highlighted that many H7 viruses adapted to infect mammals, like pigs and horses.
The authors said that they do not know what H7N9 will do next, but the H7N9 virus may be able to help scientists to prepare for future human and animal pandemics.
"We have a unique opportunity to learn more of influenza's many secrets, and thereby enhance our ability to prevent and control an important disease that seems destined to appear again and again, in multiple guises, far into the foreseeable future," the authors said.