In a worrying development, the World Health Organization is reporting that a new strain of bird flu has infected people who have reportedly never come in contact with poultry. The H7N9 strain, first discovered in humans last month, has so far been blamed for 16 deaths. Typically bird flu spreads only to those who've handled sick birds or come in close proximity to them. But a WHO spokesperson told Reuters that 40 percent of individuals with the flu don't fit that criteria, an alarming situation that heightens potential for a pandemic outbreak. Worse yet, a four-year-old has tested positive for the flu while exhibiting no ill symptoms, a situation that could make tracking H7N9 extremely difficult.

Hartl made clear that the WHO has seen no evidence that "sustained" human-to-human transmission is occurring, but he didn't dismiss the possibility. In fact, two suspected cases of inter-human transmission are currently under investigation. "It might be because of dust at the wet markets, it could be another animal source beside poultry, it could also be human-to-human transmission." Lengthy incubation periods could further obscure the exact cause of infection. Thus far China has reported 77 infections of the virus — which combines traits from three other strains— spread across 11 locations. The World Health Organization plans to dispatch a number of leading experts to help assist in researching H7N9.