Watching the new H7N9 bird flu begin its deadly spread in China offered a glimpse of what it would be like if it hit the western world. But in the case it becomes easily transmitted among people, the world is unprepared to face the consequences of the pandemic, the deputy chief of the World Health Organization (WHO) said Tuesday.

Although extensive preparations were made during the H1N1 scare of 2009-2010, "the world is not ready for a large, severe outbreak," Deputy Chief Keiji Fukuda told WHO delegates.

"When people get hit with an emerging disease, you can't just go to a book and know what to do," he added.

With the death toll at 35 and 130 infected, China has resorted to killing millions of chickens and consumers have avoided eating them, costing the poultry industry more than $6.5 billion as a result.

Researchers have no evidence of the spread of H7N9 from person to person, nor do they clearly know how poultry acts as a vehicle for transmission, but 40 percent of the infections were in people who had no contact with livestock.

"Any new influenza virus that infects humans has the potential to become a global health threat," said Margaret Chan, chief of WHO. "This is a puzzling virus, surrounded by mystery."

China also faced a deadly severe acute respiratory syndrome (SARS) outbreak in late 2003, which killed more than 300 people. Since then the government has invested heavily in preventative measures.

"Prevention and control have been proven to be effective. However, due to our limited understanding of the virus and the disease, it is imperative to be vigilant, with contingency plans," said Li Bin, China's health minister.

Just last month, the U.S. Centers for Disease Control and Prevention (CDC) made an effort to begin work on a vaccine against H7N9 strains. But many are questioning whether it will work.

The new SARS-like coronavirus also struck around the same period but originated in Saudi Arabia. Researchers say both the novel coronavirus and the bird flu were unrelated outbreaks.