As the number of confirmed human cases of swine flu rose to 1,025 in 20 countries Monday, the U.N. health agency urged governments to refrain from taking rash but unproven measures to contain the disease.
The World Health Organization's top official said countries should base their actions on scientific evidence, pointedly refraining from criticizing any specific steps governments have taken in response to the outbreak.
"Let me make a strong plea to countries to refrain from introducing measures that are economically and socially disruptive, yet have no scientific justification and bring no clear public health benefit," Margaret Chan said in a video message to the U.N. General Assembly in New York.
China angered has Mexico by quarantining more than 70 Mexican travelers even though some appeared not to be at risk of the disease. On Monday, the University of Montreal said a group of 25 Canadian university students and a professor had been quarantined at a hotel in China since the weekend over swine flu fears. Both countries have reported dozens of cases and Beijing's drastic measures appeared to be an attempt to stop the disease reaching its shores.
Chinese authorities said they have also tracked down and quarantined other passengers who were on the same flight as a Mexican traveler later diagnosed in Hong Kong with swine flu. None showed symptoms of the virus. Hong Kong _ which has its own semi-autonomous administration _ has quarantined some 274 guests and employees of the hotel where the tourist stayed.
WHO flu chief Keiji Fukuda said quarantines were a "long-established principle" that makes sense in the early phases of an infectious disease outbreak. The WHO has yet to declare a full outbreak _ or phase 6 alert _ though it has said this would likely only be a matter of time as the virus appears to be spreading to more and more countries around the world.
"As we get later on into phase 6 then these sorts of measures will become less useful because there will just be more infections around and you can't quarantine everyone in the world," he said.
"I don't want to comment on the specific disease control actions of different countries," he added after being pressed on China's quarantine measures.
Like most international organizations, WHO generally avoids open fights with its 193 member states, preferring behind-the-scenes persuasion. Critics contend that Chan's public restraint could undermine efforts to protect global health, but her defenders say she would never hesitate to do what is necessary.