Mexican officials are asking citizens to avoid large crowds, refrain from kissing as a greeting and maintain a distance of at least 1.8 meters (six feet) from each other amid growing concern in the country and elsewhere over new cases of suspected and confirmed swine flu infection.
A couple kisses through their masks at the Historic Center in Mexico City on Saturday.
Several countries issued travel notices and tightened restrictions to brace against the virus the World Health Organization is calling "a public health emergency of international concern."
By Sunday, 81 deaths had been deemed "likely linked" to a deadly new strain of the virus by health authorities in Mexico. Viral testing has confirmed 20 cases, said Dr. Jose A. Cordova Villalobos, Mexico's health secretary. In the United States, the number of confirmed swine flu cases stood at 11.
In New Zealand, officials said 22 students and three teachers, who returned from a three-week-long language trip to Mexico, may have been infected with the virus.
The 25 students and teachers at Auckland's Rangitoto College returned to New Zealand via Los Angeles on Saturday.
Fourteen have shown flu-like symptoms, with four "more unwell than others," said Dr. Julia Peters, clinical director of Auckland Regional Public Health Service.
Health Minister Tony Ryall said 10 students tested positive for influenza A. The specimens will be sent to WHO to determine whether it is H1N1 swine influenza. H1N1 influenza is a subset of influenza A.
The WHO results are expected back by midweek. The group remains quarantined at home.
"It's certainly has not been confirmed that they have swine flu," said Dr. Craig Thornley, medical officer of health in influenza. "We already have provisional information that some of the group have influenza A. We won't know if they have the type of influenza A that is swine flu."
In England, authorities stressed that a crew member who developed flu-like symptoms during a flight from Mexico City to Heathrow did not test positive for swine flu.
"I can confirm that the patient doesn't have swine flu," said Jonathan Street, a spokesman for Northwick Park Hospital in London.
"We have done all test, and they all came back negative."
In Israel, doctors are running tests on a man who recently returned from Mexico with light flu symptoms.
U.S. health officials said Friday that some cases of the virus in the United States matched samples of the deadly Mexican virus. All the patients have recovered or are expected to.
The panic over the virus prompted Canada to issue a travel health notice, saying the public health agency was "tracking clusters of severe respiratory illness with deaths in Mexico." Video Watch CBC report on Canadian microbiologists' concerns »
South Korea said it will test airline passengers arriving from the United States. And Japan will convene a Cabinet meeting Monday to come up with measures to block the entry of the virus into the country.
The United States had not issued any travel warnings or quarantines.
But US Airways said Saturday night it would allow passengers to change plans if they wanted to because of the outbreak.
