Our Expert Voices conversation on emerging diseases.

I always like to say, when predicting future disease outbreaks, what's past is prologue. More than 300 new diseases have emerged since 1940, and many of these have been the result of spillover from wild animal to human populations.

Zoonotic outbreaks are expected to increase as the buffer between humans and animals decreases and a disease can travel with humans from even the most remote region of the world to the other side of the globe within 24 hours.

We need better disease surveillance in human populations – especially those who are frequently in contact with wildlife. We should also be monitoring wildlife populations for changes such as die offs or major shifts in density or behavior that often precede zoonotic outbreaks in human populations.

Bottom line: We can't stop diseases from spilling over from animals to humans, but we can limit the extent of their spread and impact with good disease surveillance systems in place and the ability to rapidly respond. We must be ready to expect the unexpected.

Other voices in the conversation:

• Thumbi Mwangi, veterinarian, Washington State University: Control small diseases to be ready for big ones
• Justin Lessler, epidemiologist, Johns Hopkins University: It's not where a virus comes from but how it becomes contagious
• Kevin Olival, ecologist, EcoHealth Alliance: There are 5,000 places to look