WASHINGTON (Reuters) - The new H1N1 influenza virus bears a disturbing resemblance to the virus strain that caused the 1918 flu pandemic, with a greater ability to infect the lungs than common seasonal flu viruses, researchers reported on Monday.
Tests in several animals confirmed other studies that have shown the new swine flu strain can spread beyond the upper respiratory tract to go deep into the lungs -- making it more likely to cause pneumonia, the international team said।
In addition, they found that people who survived the 1918 pandemic seem to have extra immune protection against the virus, again confirming the work of other researchers.
"When we conducted the experiments in ferrets and monkeys, the seasonal virus did not replicate in the lungs," said Yoshihiro Kawaoka of the University of Wisconsin, who led the study।
The H1N1 virus replicates significantly better in the lungs."
The new swine flu virus has caused the first pandemic of the 21st century, infecting more than a million people, according to estimates, and killing at least 500। The World Health Organization says it is causing mostly moderate disease but Kawaoka said that does not mean it is like seasonal flu।
"There is a misunderstanding about this virus," he said in a statement. "There is clear evidence the virus is different than seasonal influenza."
Writing in the journal Nature, Kawaoka and colleagues noted that the ability to infect the lungs is a characteristic of other pandemic viruses, especially the 1918 virus, which is estimated to have killed between 40 million and 100 million people।
OLD PROTECTION
They tested the virus in blood samples taken from nursing home residents and workers in 1999 in California, Wisconsin, the Netherlands and Japan.
People born before 1920 had a strong antibody response to the new H1N1 virus, meaning their body "remembered" it from infection early in life। This finding supports a study published in Nature in August that also found people who survived the 1918 pandemic still had immune protection against that virus।
Flu viruses change constantly, which is why people can be re-infected and why the vaccine must be changed regularly। Current seasonal strains of H1N1 are distant cousins of both the 1918 pandemic strain and the new H1N1 strain।
"Our findings are a reminder that swine-origin influenza viruses have not yet garnered a place in history, but may still do so, as the pandemic caused by these viruses has the potential to produce a significant impact on human health and the global economy," the researchers wrote.
Other tests showed the virus could be controlled by the antiviral drugs Relenza, made by GlaxoSmithKline, and Tamiflu, made by Roche AG, the researchers said।
The World Health Organization said on Monday that vaccine makers should start making immunizations against H1N1 and that healthcare workers should be first in line to get them।
Companies working on an H1N1 vaccine include Sanofi-Aventis, Novartis AG, Baxter International Inc, GlaxoSmithKline, Solvay and nasal spray maker MedImmune, now part of AstraZeneca.
(Editing by Doina Chiacu)
Experts unearth history of pandemic flu viruses
By Tan Ee Lyn
HONG KONG (Reuters) - Flu viruses that sparked the three worst pandemics in the last century circulated in their near-complete forms for years before the catastrophes occurred, researchers in Hong Kong and the United States have found.
The H1N1 virus that sparked the Spanish flu of 1918-1919 circulated in swine and humans well before the pandemic started, and it did not come directly from birds as previously thought, they added. Instead, it was probably generated by genetic exchanges between flu viruses from swine and humans.
This contrasts sharply with previous studies which suggested that the H1N1 virus of 1918 was a mutant that jumped direct from birds to human and ended up killing as many as 50 million people.
The findings are considered important because of the lack of studies of the virus in animals before the current outbreak of H1N1. Through understanding the natural history of viruses, monitoring of current viruses can be fine-tuned, the team from the University of Hong Kong and St Jude Children's Hospital in the United States wrote.
Published in the Proceedings of the National Academy of Sciences, the study also involved two other pandemic viruses
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the H2N2 responsible for the Asian flu of 1957, and the H3N2 which sparked the Hong Kong flu of 1968।
Guan Yi, microbiologist at the University of Hong Kong and member of the research team, said the viruses of 1918 and 1957 went through at least two rounds of reassortments before the pandemics occurred. Reassortments happen when flu viruses swap genetic material, which happens when an animal or person is infected with two strains at the same time.
"Before, people did not know how pandemic viruses came about ... this study gives us a deeper understanding into the evolution and emerging process of pandemic viruses," Guan said।
Another finding was that the H1N1 pandemic virus of 1918, the seasonal H1N1 virus of today and the classical H1N1 swine virus may have been co-circulating in the 1918-1919 period.
"All three are different viruses but related ... which would explain why some waves of the (1918-1919) pandemic were more deadly than others," Guan said।
The team analyzed and compared the genes of the 1918, 1957, and 1968 viruses and their close relatives to determine their ancestry and the gene exchanges that created them.
The genes of the 1918 virus likely circulated in swine and humans from as early as 1911, and the virus was unlikely to have been transmitted directly from birds to humans, Guan said।
"It is very difficult for viruses to jump directly from bird to human (and cause a pandemic), which may explain why the H5N1 virus hasn't caused a pandemic so far (by making that direct jump from bird to human)," Guan said।
The H2N2 (1957) and H3N2 (1968) reassortant viruses formed similarly, through exchanges with unknown mammalian hosts and input from bird viruses।
"Because of a lack of sequence data for swine influenza from these periods, the involvement of swine in the generation of these pandemic strains cannot be precluded," the paper said.
(Editing by Nick Macfie)
U.S. to spend another $1 billion on flu Vaccine
WASHINGTON (Reuters) - The United States will spend another $1 billion on ingredients for an H1N1 vaccine, U.S. Health and Human Services Secretary Kathleen Sebelius said on Sunday.
"There'll be another $1 billion worth of orders placed to get the bulk ingredients for an H1N1 vaccination। Congress has agreed with the president that this is the number one priority, keeping Americans safe and secure," Sebelius said on CNN.
Sebelius has said plans were on track for a mid-October vaccination program, although it was not certain Americans would be offered the vaccine for the so-called swine flu।
"We are aggressively working on, first of all, testing the virus strains to get a vaccination ready। It needs to be safe so testing and clinical trials will start this month। We'll know a lot more by the end of the summer and it needs to be effective," she said।
The World Health Organization may issue guidance as soon as Monday on whether an H1N1 swine flu vaccine will be offered alongside the seasonal flu vaccine.
Vaccine makers Sanofi-Aventis, Novartis, Baxter, GlaxoSmithKline, Solvay and AstraZeneca's MedImmune subsidiary have finished making seasonal flu vaccines for this year।
The U.S. Food and Drug Administration has scheduled a July 23 advisory panel meeting to discuss clinical trials of the vaccines against the H1N1 influenza virus and the U.S. Advisory Committee on Immunization Practice wills meet July 29.
"FDA is working with the scientists at NIH (National Institutes of Health) to make sure that we have a safe and effective strain and then we're getting ready to make sure that we have a vaccination program," Sebelius said।
Health experts estimate at least 1 million people have been infected with H1N1 in the United States, and the U.S. Centers for Disease Control and Prevention has confirmed 211 deaths. It often takes weeks or months to collect data on flu deaths.
About 36,000 people die each year from the seasonal flu in the United States alone, and 250,000 to 500,000 die globally।
(Editing by Maggie Fox)
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