GENEVA (AFP) - - Swine flu will spread further across the world, experts at the World Health Organisation warned Friday, as the number of confirmed cases surged by more than 1,000 and the US reported two more deaths.
Acting WHO Assistant Director-General Keiji Fukuda told reporters that studies by experts indicated a "significant number of people" had been infected, but remained undetected or unconfirmed by laboratory tests.
"Their work also suggests that the virus is transmissible enough that we will expect to see continued community level outbreaks and regional spread," he told a WHO meeting in Geneva on pandemic preparedness.
The latest WHO data showed 7,520 people in 34 countries were confirmed to have caught the influenza A(H1N1) virus, up 1,000 from Thursday.
According to the figures, most of the deaths had occurred in Mexico, where the Mexican officials said death toll rose by two on Friday to 66 with the epidemic having sickened 2,829 people there.
"We cannot know when we will have it contained," Mexican Health Minister Jose Angel Cordova admitted at his daily press briefing.
But, he said, "I expect in this month or next we can be very close ... and that most of the cases will be sporadic."
US health officials also upped the number of US deaths from three to five, reporting that one person had died in Arizona as well as a young man in Texas. Of the three previous US deaths, two were in Texas and one was in Washington state.
The US Centers for Disease Control and Prevention (CDC) said the number of confirmed and probable cases had reached 4,714, with only four states -- Alaska, Mississippi, West Virginia and Wyoming -- having been spared so far.
On Friday, New York City authorities were forced to close three schools, sending home 4,500 students, after an assistant principal of one of the schools was hospitalised in serious condition.
But US officials are poised to relax a travel advisory for Mexico, some three weeks after warning against non-essential travel to the country, which had been at the epicentre of the outbreak.
"Later today, the CDC will likely be posting a downgrade to the travel warning that regards Mexico," Martin Cetron, CDC head of the global migration and quarantine division.
"The warning, which is at a level four alert, will be downgraded to a travel precaution which will focus on those individuals at high risk for complications from influenza," he said.
WHO Director-General Margaret Chan noted the virus had "quickly demonstrated its capacity to spread easily from one person to another, to spread widely within an affected country and to spread rapidly to additional countries."
"We expect this pattern of international spread to continue," she said.
"This is a time of great uncertainty, and great pressure on governments, ministries of health and WHO," she added.
Fresh updates continued to come in from governments around the world, as Ecuador said it had found its first case.
The 11-year-old victim in the port city of Guayaquil arrived from Miami in the United States only days earlier, reported an official, who requested anonymity.
Meanwhile, experts warned that the fallout of the swine flu epidemic is hitting the travel industry hard, and international tourism risks sliding heavily if the swine flu spread is upgraded to a pandemic.
"The probability of a full blown pandemic is relatively low, but there might be another outbreak in full force of swine flu in the next winter in the northern hemisphere," an economist at Britain's Oxford Economics firm, John Walker, told AFP.
If that happened the number of passengers could drop "up to 60 percent," he warned.
The WHO's Fukuda said the behaviour of the virus would change depending on "whether it is winter period in one part of the world or another."
The virus had "a very different pattern" from normal, seasonal flu, warned Fukuda: half of those who had died had been young and otherwise healthy adults.
"Right now we don't know what the future will bring," he added.