World Health Organization officials said China’s crackdown on parts of the country bought time for the rest of the world to prepare for the new virus. But as hot spots emerge around the globe, trouble finding each source — the first patient who sparks every new cluster — might signal the disease has begun spreading too widely for tried-and-true public health steps to stamp it out.

“A number of spot fires, occurring around the world is a sign that things are ticking along, and what we are going to have here is probably a pandemic,” said Ian Mackay, who studies viruses at Australia’s University of Queensland.

That worst-case isn’t here yet, the WHO insists. It isn’t convinced that countries outside China need more draconian measures, but it pointed to spikes in cases in Iran and South Korea to warn that time may be running out to contain the virus.

“What we see is a very different phase of this outbreak depending where you look,” said WHO’s Dr. Sylvie Briand. “We see different patterns of transmission in different places.”