H7N9 is a virus worth worrying about

摘要

Once again an animal influenza A virus has crossed the species barrier to cause an appreciable number of human cases. Now, two months after the first known human infections with the H7N9 virus, the question is: which of the paths set by previous emerging influenza viruses will it follow? One predecessor, H5N1, generated alarm owing to its high patho-genicity in humans. It has proved to be a tenacious adversary, remaining endemic in poultry across large parts of Asia, but thankfully it has not adapted to humans and person-to-person transmission remains rare. A second, H7N7, caused a number of mostly mild human infections in the Netherlands in 2003, with some evidence of limited person-to-person spread, but extensive poultry culling controlled it.