The H7N9 Reassortment – Credit Eurosurveillance
# 7146
With the caveat that everyone – including the CDC, World Health Organization, ECDC, and Hong Kong’s CHP – must currently make assessments of the threat posed by the H7N9 avian flu based on incomplete (and constantly changing) information, many experts are concerned over what they have seen to date.
Perhaps most ominously, H7N9 can spread among birds (presumably both migratory and poultry) without overt signs of infection, making its detection and eradication particularly difficult.
And unlike other H7 avian flu viruses we’ve seen (see A Brief History Of H7 Avian Flu Infections) this new reassortant bird flu causes severe illness in some (as yet, undetermined) percentage of humans who contract it.
Early genetic sequencing has shown that not only are there worrisome changes in the virus suggesting adaptation to mammals (see Webby On H7N9: `Clear Evidence Of Mammalian Adaptation’), there are also signs that the virus is still mutating and evolving at a substantial rate (see Reuters Analysis: New China bird flu a moving target).
As Helen Branswell reported yesterday (see Branswell: World In `New Territory’ With H7N9 Flu – WHO’s Fukuda), there is a palpable sense of uneasiness in the scientific community over what this virus might do.
So, with the understanding that no one really knows what will happen next, a few choice quotes (with links) from some of the world’s best flu experts.
First, from Zhong Nanshan, a genuine hero of the SARS epidemic 10 years ago and director of Guangzhou's Institute of Respiratory Diseases, these quotes from a new CCTV report dated 4/16/2013.
"We haven’t got an effective treatment regimen yet. But what we can do is to make an early diagnosis of the patients with symptoms of H7N9 virus. The earlier they get to ICU, the more chance they have to survive. Every hour, every minute counts."
"We cannot rule out the possibility that it is coming from migrant birds. But it’s not the only explanation. The virus comes from a gene mutation, which can happen in any location. Generally speaking, cities are an easier target for the virus, due to dense population and intensive contact."
"In terms of the public, as there is no evidence of human-to-human transmission so far, we don’t need to escalate the tension and scare the public. But for the government, we should intensify our efforts to carry out wider and stricter monitoring of the H7N9 strain."
Declan Butler’s latest report in the journal Nature, contains quotes from a variety of experts, including Jeremy Farrar, director of the Oxford University Clinical Research Unit in Vietnam and Marc Lipsitch, an epidemiologist at the Harvard School of Public Health in Boston.
Ferrar states: “This looks very different from H5N1. We never saw this number of presumed avian/animal to human transmissions in such a short space of time."
And Lipsitch is quoted: “It's too soon to say how big a threat H7N9 poses because we don't know how many animals of which species have it, how genetically diverse it is, or what the geographic extent is. It looks as though it will be at least as challenging as H5N1."
Too good to simply quote from, you’ll want to follow the link below to read it in its entirety.
H7N9 bird flu poised to spread
Via the Australian Science Media Centre (AusSMC) RAPID REACTION: Bird flu (H7N9) in China – experts respond. Professor Adrian Sleigh from the National Centre for Epidemiology and Population Health at The Australian National University.
“The 3 deaths from H7N9 flu virus is of some concern. The H7 family of viruses are bird flus that have crossed to poultry workers many times (respiratory infection and conjunctivitis) – but usually as benign infections. In 2008 Jessica Belser published evidence that H7 viruses were becoming more transmissible among humans. In March this year the Australian Government reported to WHO a small outbreak of H7N7 on a poultry farm in NSW, which was ‘stamped out’. Now we have to wait to see if the is any interaction among the cases in China or indeed any evidence of human-to-human transmission. Each case must be investigated for recent exposure to other sick people or sick birds and all local bird flocks must be checked too.”
For details on the Belser H7 study mentioned above, you can revisit my 2008 blogs CDC Press Release On Adaptation Of H7 Viruses. H7's Coming Out Party and H7 Study Available Online At PNAS
This morning, from a Hong Kong Standard report entitled Lack of symptoms in bird flu boy worries diseases expert, Professor Yuen Kwok-yung from the University of Hong Kong's department of microbiology, expressed concerns that - asymptomatic carriers of the new bird flu strain will make it difficult for authorities to control the virus especially if there is human-to- human transmission.
And finally, from the Reuters, a long article with many quotes called Analysis: New China bird flu a moving target, a quote from Ab Osterhaus, head Virologist at the Erasmus Medical Center in the Netherlands that shows how much more we need to learn.
"We know H7 viruses can spill over into humans ... and for me the most important thing to find out now is from which species do we think this H7N9 is spilling over. Is it one species? Are there different species? At this stage we are still lacking a lot of data."
For now, H7N9 presents an epidemiological mystery and an, as yet, uncertain public health threat.
Later this week representatives of the CDC and the World Health Organization will arrive in China for a first hand look at the situation (see China: MOH Invites Outside Experts On H7N9).
Hopefully we’ll know a lot more about this virus, and its potential, after they’ve had a chance to evaluate the evidence.
