February 5, 2014
Novel Bird Flu H10N8 Has Potential To Become Pandemic
Lawrence LeBlond for redOrbit.com - Your Universe Online
While China has already been dealing with one avian influenza outbreak – H7N9 – a novel strain has emerged, killing its first victim in December. The new strain, H10N8, infected another person last month and experts are now concerned of the potential for another pandemic.
They say the virus appears to be able to infect deep lung tissue and may be able to spread more efficiently among humans than previous bird flu strains.
"The pandemic potential of this novel virus should not be underestimated," said the research team, as cited by The Telegraph.
The new warnings stem from a genetic analysis of the H10N8 strain after samples had been taken from the 73-year-old woman who died in Nanchang, Jiangxi Province in December. A paper on the genetic findings has now been published in The Lancet medical journal.
The study team found that the new strain had genetic similarities to two other types of avian influenza – H5N1 and H7N9 – both of which have been causing headaches for Chinese health officials in recent times. H5N1 was first recorded in 2003 and has killed at least 384 people since. H7N9 is a continuing outbreak that began infecting humans last year. After a lull in the number of cases, that strain has picked up steam and has infected more than 125 people since the New Year began, killing at least 25.
With H10N8, the researchers said there have been no reported outbreaks yet in poultry, noting that it could be quietly spreading through flocks. However, the strain has been detected twice before, once from a water sample from a lake in Hunan in 2007 and once from live poultry in Guangdong in 2012.
The first two human cases have shown no signs of human-to-human transmission capabilities but the researchers caution that this should not be taken lightly. The team noted that H10N8 could easily develop sustainability among humans in the future, as the researchers have found some evolution in the genetic profile of the virus, allowing for more efficient human replication.
"[The] second case of H10N8 was identified in Jiangxi province, China, on 26 January 2014. This is of great concern because it reveals that the H10N8 virus has continued to circulate and may cause more human infections in future," said Dr Mingbin Liu, of Nanchang City Centre for Disease Control and Prevention.
"The potential epidemiological significance of this zoonotic infection is not clear. Avian influenza viruses of the sub-type H10N8 are probably not particularly unusual. Whether there were complications in this case is unclear,” added Dr John McCauley, director of the WHO Collaborating Centre for Influenza and MRC's National Institute for Medical Research.
"This case reminds us to be aware of human infections from animal influenza viruses, like the H7N9 cases in China which increase daily. Previously we did not think that H7N9 infections might be so lethal. Now we also must consider H10N8 infections as well," he told the BBC.
As for the H10N8 strain, genomic sequencing on the samples have established that it is a new genetic reassortment avian-origin virus (JX346). Particularly interesting is the fact that genome testing indicated that six of the strain’s internal genes derived from avian H9N2 viruses that have been circulating among poultry in China.
"A genetic analysis of the H10N8 virus shows a virus that is distinct from previously reported H10N8 viruses having evolved some genetic characteristics that may allow it to replicate efficiently in humans. Notably, H9N2 virus provided the internal genes not only for the H10N8 virus, but also for H7N9 and H5N1 viruses," explained Dr Shu in a statement.
The results of the genetic sequencing of the first sample, suggest that “JX346 might originate from multiple reassortments between different avian influenza viruses. The H10 and H8 gene segments might have derived from different wild bird influenza viruses reassorted to give rise to a hypothetical H10N8 virus in wild birds, which infected poultry and then reassorted with H9N2 viruses in poultry to give rise to the novel reassortant JX346 (H10N8) virus", said Dr Shu.
"Importantly, the virus had a mutation in the PB2 gene that is believed to be associated with increased virulence and adaption in mammals, and could enable the virus to become more infectious to people," explained coauthor Dr Qi Jin, of the Chinese Academy of Medical Sciences and Peking Union Medical College in Beijing.
Further investigation revealed the woman who died in December had visited a live poultry market just days before infection, suggesting the incubation period is about four days, similar to most avian influenzas. However, no H10N8 virus has been found in samples collected from the poultry site the patient visited.
CIDRAP’s Robert Roos reported that researchers also believe the patient’s chronic medical conditions could have played a major role in her death. However, the team did find that the novel virus was “overwhelmingly dominant” in her tracheal specimens, which indicated that the virus had some involvement in the woman’s death.
“In addition, they found a mixture of glutamic acid and lysine at residue 627 in the virus's PB2 protein, a mutation that is associated with adaptation to, and can increase virulence in, mammals,” wrote Roos.
“Further, the authors report that the novel virus preferentially binds avian-like alpha2,3-linked sialic acid receptors, which are "dominant in human lung tissue," suggesting a potential for the kind of lung damage found in human H5N1 infections,” he continued.
The team concludes that the first known human cases of H10N8 infection “further increases the importance of surveillance for pandemic preparedness and response.”