A virologist tests samples for signs of swine flu at Sydney's Prince of Wales Hospital ... infections may be as high as 100,000 in the U.S. alone
Credit: Torsten Blackwood/AFP
PARIS: Swine flu infections may be 20 times higher than so far detected, but the chances of a common vaccine for all strains are high after a study found they react to antibodies in the same way.
Published in the U.S. journal, Science, the study says the various A(H1N1) virus strains have probably been circulating unnoticed in pig populations for some time, and calls for more careful monitoring of swine populations.
It confirms that the new pathogen originated with pigs, and is a mix of a previously known virus that already contained avian, swine and human genetic segments with two other genes from Eurasian swine viruses never detected outside Asia before.
Understanding origins
Understanding the origins of the novel A(H1N1) virus could help scientists prevent the pathogen from emerging in a new - and potentially more virulent - form, the researchers said.
"These findings are critically important for our global public health," said Nancy Cox, chief of the influenza division of the U.S. National Centre for Immunisation and Respiratory Diseases in Atlanta, Georgia, and a co-author of the study.
"The new A(H1N1) viruses are antigenically similar, that is, they react to antibodies in a similar way," she told journalists in a teleconference. "This makes our job of coming up with a reference candidate vaccine virus much, much easier."
Differences with seasonal flu
Cox cautioned, however, that the swine flu was very different than seasonal flu, meaning that vaccines designed for the latter probably would not work against both.
The number of confirmed swine flu infections worldwide topped 11,000 Friday, including more than 85 deaths, according to the World Health Organisation.
A total of 11,168 infections had now been detected in 41 countries. The United States had 5,764 cases, with nine deaths, while Mexico had 3,892 infections, including 75 deaths. Canada had 719 cases, with one death.
Japan reported 294 cases, making it the hardest hit outside North America. In Europe, Spain had the highest number of infections - 113 cases - and Britain had 112.
Australia on Thursday reported two new infections of swine flu in a young child and a Mexican woman, raising the country's cases to seven as authorities closed a school and warned the virus would "inevitably" spread.
Nicola Roxon, Australia's Health Minister, announced on Wednesday that a Melbourne primary school had been closed until next week and 51 students provided with anti-viral drugs after two brothers diagnosed with swine flu.
Poorly resourced
The U.S. Centres for Disease Control and Prevention (CDC) says it believes the real tally - in the U.S. at least - was probably 20 times higher. It may be even worse in the developing world: WHO officials have said poorer countries may not have the resources to detect all cases of the new virus. In some countries, their priority goal may not be to tally all cases but to track its geographic spread and severity.
"This is the tip of the iceberg - we estimate more than 100,000 cases," Anne Schuchat, the CDC's deputy director for science and public health, told journalists.
While the rate of new U.S. infections had tapered off over all, the virus remained "very, very active" in some regions, she said. "We should expect to see more cases, more hospitalisations, and perhaps more deaths in the coming weeks."
She cautioned travellers to take precautions, and especially to not travel with sick family members. The virus could continue to circulate in the northern summer "and come back in the worst way in the fall [autumn]," she said.
For the study, scientists sequenced the genomes of more than 70 samples of the novel H1N1 flu, 17 from Mexico, and 59 from 12 states in the United States. The study provides the first detailed analysis of the pathogen's genetic and antigenic – how it reacts to antibodies - characteristics.
It is still unclear whether the new flu entered the human population directly from pigs, or whether there was an intermediate host, Cox said.
with Cosmos Online
