Studies of viruses, conducted by specialized WHO reference laboratories, can corroborate field investigations by spotting genetic and other changes in the virus indicative of an improved ability to infect humans.

• WHO专门的参考实验室对病毒进行研究，定位病毒遗传或其它方面的突变，确定病毒感染人的能力增强，从而确认现场调查。