Scientists taking a first look at the genetics of the bird-flu strain that killed three people in China yesterday said that the virus could be harder to track than its better-known cousin H5N1, because it might be able to spread silently among poultry without notice.
The scientists, at several research institutes around the world, said the H7N9 virus seems troubling because it can generate no symptoms in poultry, while seriously sickening humans. They said the virus, previously known to have infected only birds, appears to have mutated, enabling it to more easily infect other animals, including pigs, which could serve as hosts spreading the virus more widely among humans.
The findings are preliminary and need further testing.
The scientists said that based on information from genetic data and Chinese lab testing, the H7N9 virus appears to infect some birds without causing any noticeable symptoms.
Without obvious outbreaks of dying chickens or birds to focus efforts on, authorities could face a challenge in trying to trace the source of the infection and stop the spread.