November 14, 2013
First Human Becomes Infected By H6N1 Bird Flu In Taiwan
Lawrence LeBlond for redOrbit.com - Your Universe Online
As parts of Southeast Asia continue to struggle with H7N9 and H5N1, one particular bird flu strain that has never been associated with humans has now made the jump. A new report has confirmed that a 20-year-old Taiwanese woman tested positive for the disease earlier this year.
Known as H6N1, the avian influenza strain was detected in the patient after she had made several trips to two local hospitals due to fever and trouble breathing. After being admitted on her third visit (May 8), doctors determined she had a lower respiratory infection, but throat cultures did not return signs of any known flu strain.
Further testing ruled out Legionnaire’s disease and mycoplasma pneumonia. Despite not knowing the cause of the infection, the doctors treated the patient with Tamiflu and Levaquin. Her symptoms began improving the following day, and she was discharged two days later. A follow-up X-ray a week later showed that her respiratory infection had also cleared up.
While the woman mad a complete recovery, experts from Taiwan’s Centers for Disease Control and area hospitals and institutions continued their probe into the mysterious infection. Using a genetic test known as real-time RT-PCR, the scientists came up with a match for H6N1 influenza in early June.
In a paper, published in today’s issue of The Lancet Respiratory Medicine, researchers from the Taiwan CDC have made the confirmation that the 20-year-old Taiwanese woman gets the honor of being the first human to become infected by H6N1.
The experts’ analysis shows that the H6N1 virus isolated from the woman is most closely related to poultry from Taiwan, suggesting that the virus originated from that poultry. The researchers noted that this particular virus “had a G228S substitution in the haemagglutinin (HA) protein that might increase its ability to infect human cells. In addition, based on the sequences of the NA protein, the virus is susceptible to neuraminidase (NA) –inhibitors such as Oseltamivir and Relenza.”
During the investigation, the Taiwan CDC also investigated 36 close contacts of the patient, in which none were found to be infected with the H6N1 avian flu strain. And after conducting enhanced influenza surveillance in patients that had visited three hospitals and seven clinics within a five-mile-radius of the initial patient’s residence for three months, no other H6N1 illnesses were detected – in all 178 influenza-like specimens were tested during the 90-day period. Furthermore, a widespread test of 6,985 respiratory specimens collected in 2013 have also not been attributed to H6N1.
An even more detailed genetic analysis of the virus sample from the Taiwanese patient has revealed that seven of its genes were closely related to a flu strain isolated from Taiwanese chickens this year. However, the eighth gene was more closely related to another strain found in Taiwanese chickens in 2002. Versions of the H6N1 virus that sickened the woman have been infecting chickens since 1997, and some other versions of the virus have been prevalent in chickens since 1972, the researchers noted.
Based on the evidence from the Taiwan CDC research, no evidence of sustained avian-to-human or human-to-human transmission of the virus in the community exists. Health and agricultural experts maintained that they would continue to monitor the situation and reinforce their surveillance efforts in humans, poultry and the environment.
While this seems likely to be just a single isolated case, it still paints a pretty clear picture that avian influenza is unpredictable and has the potential to cause a widespread epidemic in a population.
The current H7N9 avian influenza outbreak that has been plaguing China since March, is one sign that a bird flu strain can be unpredictable.
According to the World Health Organization (WHO), H7N9 has caused 139 illnesses and 45 deaths so far. In April, after the link to poultry was made, the Chinese government took control by culling millions of birds, which successfully diminished the number of cases reported. From between the first of May and the end of September, only a handful of cases were reported. However, since the beginning of October, case numbers are starting to pick up once again, with the latest report coming November 6, with two new lab-confirmed cases.
While H7N9 is far from pandemic level, nor is the 1996 H5N1 outbreak that has been continuing to infect humans, killing more than 600 since first being detected, concerns arise over how easily such viruses may be able to infect people.
"The question again is what would it take for these viruses to evolve into a pandemic strain?" Marion Koopmans, DVM, PhD, a virologist at the National Institute for Public Health (RIVM) and the Environment in the Netherlands, wrote in a commentary that accompanied the new report.
Koopmans said it is very concerning that scientists had no early warnings that new bird flus like H7N9 and H5N1 could pose a problem to humans, not until people became ill, that is. Birds are usually monitored closely to see which viruses are killing them in order to determine which ones might be troublesome to humans. But what was most worrisome was the fact that neither H7N9 nor H6N1 appeared to make birds very sick.
She warned that increased surveillance is necessary to get a better handle on which animal viruses are capable of making the jump to humans and which ones could likely cause a global crisis. "We can surely do better than to have human beings as sentinels."
While H6N1 jumping to humans was a complete shock for experts, most agree that H7N9 still remains far of a worry.
Richard Webby, PhD, of St. Jude Children’s Research Hospital in Memphis, Tenn., who is also a director of the WHO collaborating center for influenza in the US, told MedPage Today that "the H7N9 does seem to be a more infectious virus and certainly concerns me more than the H6."
In order for these bird flu strains to evolve into pandemic strains they must be able to take one big step, according to the Taiwan CDC researchers. It appears that such strains have an affinity for human lung tissue. Genetic analysis has found that bird flu strains that infect humans prefer to bind to alpha2-6 sialic acid receptors, a step up from the avian strains that only infect alpha2-3 sialic acid receptors in birds.
"For these avian flu viruses to adapt to humans, they really do have to change the sialic acid, the receptor of the human host cell that the viruses bind to," Webby said, adding that the novel virus has a "signature molecular change that we do associate with at least going down that pathway.”
However, he said, it remains unclear what other changes might be needed to make the virus more of a threat to humans.
But by comparing the new H6N1 strain with others – such as the H7N9 strain – scientists may be able to better predict which avian pathogens are likely to infect humans, he added.
In respect to the new H6N1 case, Professor Wendy Barclay, from Imperial College London, told the BBC’s James Gallagher that it is also unknown if infections of this sort have happened in the past. Perhaps it is only that our improved technology has allowed us to make such a discovery as this one.
“Is this a truly new thing or are we now just better at seeing it?" She ponders, noting that she does expect more cases similar to this one to be reported in the coming years as more hospitals are geared up to look for novel flu strains.
"This is a single case with no evidence of human transmission, but as always we should keep an eye on it and do studies to see how close it is to being able to spread between humans," said Barclay.