Reports have put the likely death toll from the virus at 152, with Mexican officials confirming 20 deaths.

The number of cases under observation in Mexico alone has reportedly reached 1614.

But Vivienne Allan, from WHO's patient safety program, said the body had confirmed that worldwide there had been just seven deaths - all in Mexico - and 79 confirmed cases of the disease.

"Unfortunately that (150-plus deaths) is incorrect information and it does happen, but that's not information that's come from the World Health Organisation," Ms Allan told ABC Radio today.

"That figure is not a figure that's come from the World Health Organisation and, I repeat, the death toll is seven and they are all from Mexico."

Ms Allan said WHO had confirmed 40 cases of swine flu in the Americas, 26 in Mexico, six in Canada, two in Spain, two in the UK and three in New Zealand.

Ms Allan said it was difficult to measure how fast the virus was spreading.

She said a real concern would be if the flu virus manifested in a country where a person had had no contact with Mexico, and authorities were watching all countries for signs of that.

"There is no pattern that has emerged at this stage to be able to say that it is spreading in a particular way or it is spreading into a particular country ... the situation is continuing to evolve," she said.

She said the WHO was not recommending against overseas travel, but urged those who felt sick to stay home and others to ensure they kept their hands clean.

No decision had yet been made about vaccinations.

"This virus is not airborne, it's caused by droplets ... so it's not a time for worry. It's a time to be prepared," Ms Allan said.