Many United States residents have been following the H7N9 virus, or “bird flu”, outbreak that has affected Eastern China. Worrying whether or not the flu will spread to the U.S. is only natural. Despite reports that the flu has not been spreading interpersonally, according to a post by Dr. Anthony Komo (Editor-in-Chief of Harvard Health Publications) on the Chicago Tribune website, there is no concrete indication that the flu will not hit the U.S.

According to the U.S. Centers for Disease Control and Prevention and a group from China, there are no signs the virus is being passed from person to person. There are also no reports of the disease spreading outside of Eastern China.

The group from China posted a report in the New England Journal of Medicine. The three individuals discussed in the report had all contracted the H7N9 strain of flu and all died.

According to the CDC at the end of April, 126 human cases of bird flu were reported. Most of the infected were in their older years, with ages at an average of 60. In addition the flu was only passing form animal to human and no one traveling from China to the U.S. brought the virus with them upon their arrival.

Regardless of these encouraging signs, health agencies everywhere are carefully watching the situation in China. Why? Because as Komo puts it, “a virus that cannot spread easily from one person to another can change or swap genes--and suddenly be capable of spreading easily.

“We know of no reason why this could not happen with H7N9. And we know that it can produce severe, even fatal, illness,” he adds.

Discussing the potential severity a flu virus can possess, Komo refers to a particlular flu outbreak in the United States. The outbreak, which occurred in 1918, took the lives of at least 20 million people—more than the casualties from World War I. At its worst, it claimed the lives of 200 people per day.

Currently, researchers and scientists are working hard to combat the flu. However, recently the H7N9 strain has shown resistance to its only known cure.