Yet weather is becoming more extreme and unpredictable."

VOA: special.2009.11.23

She says people must keep up their guard against the virus, which is unpredictable and could change into a far more dangerous form.

VOA: standard.2009.12.29

She says the onset of maternal complications is unpredictable, and the response is often slowed by what health experts call "the three delays".

VOA: standard.2009.11.10

World Health Organization Director-General Margaret Chan said the alert level was stepped up because influenza viruses are unpredictable and can spread quickly around the world.

VOA: standard.2009.04.29