Is H7N9 Spreading from Human to Human in China?

[gsgs]

Re: Is H7N9 Spreading from Human to Human in China?

mice first, then chickens, then ..., then children
(if it works)
I read one report about such chickens some years ago,
but never heard it again. Apparently it didn't work so well
as announced or the chickens were too expensive

I can't find it now

[Emily]

Re: Is H7N9 Spreading from Human to Human in China?

http://www.nytimes.com/2013/04/09/wo...-flu.html?_r=0

China Reports New Cases of Bird Flu
By KEITH BRADSHER
Published: April 8, 2013
HONG KONG ? Chinese and World Health Organization officials said Monday that they had still not yet found any human-to-human transmission of a spreading form of avian influenza, after confirming five more infections among humans over the weekend and three more on Monday.
[snip]
Chinese officials are still investigating two families in which multiple cases of H7N9 are suspected, according to the W.H.O. One of the cases involves an 87-year-old man who died on March 4 and was later found to have had the disease. Two of his sons developed severe pneumonia about the same time, and one died on Feb. 28. But while severe pneumonia is rare, H7N9 has not been confirmed in either of the sons. And even if it had, the sons, as well as their father, could have been infected through animals instead of humans.

The Chinese authorities have not released details of the other family under investigation...

I suppose it's also possible that instead of H7N9, the infection in common could be a new zoonosis that interferes with the immune response of the respiratory system. It could be so novel in humans that it isn't even being tested for.

[jflorida]

Re: Is H7N9 Spreading from Human to Human in China?

Hopefully not a issue in the bird tests, or at least in this case but it was a interesting read :

Inability of Real-Time Reverse Transcriptase PCR Assay To Detect
Subtype H7 Avian Influenza Viruses Isolated from Wild Birds [ http://jcm.asm.org/content/46/5/1844.full.pdf ]

[AlaskaDenise]

Re: Is H7N9 Spreading from Human to Human in China?

Hopefully not a issue in the bird tests, or at least in this case but it was a interesting read :

Inability of Real-Time Reverse Transcriptase PCR Assay To Detect
Subtype H7 Avian Influenza Viruses Isolated from Wild Birds [ http://jcm.asm.org/content/46/5/1844.full.pdf ]

Hopefully that has been corrected since the paper was written in 2008. That means the 163,451 tests in their database by 2006 may contain erroneous results! While they say the problem was eventually found to be a probe mismatch, perhaps it indicates how well infuenza can adapt for different species of one host type.

.

[jflorida]

Re: Is H7N9 Spreading from Human to Human in China?

I hope it isnt a issue here for the wild bird tests if they are using the same procedure.

I looked up that H7N7 outbreak in the Netherlands back in 2003 if any of you remember that - a vet died - and here is that article if someone is interested:

Transmission of H7N7 avian influenza A virus to human beings
during a large outbreak in commercial poultry farms in the
Netherlands [ http://www.impact.arq.org/doc/kennis...00010929-1.pdf ]

Virological analysis
The proportion of samples positive for A/H7 was highest in
the first 4 days from the onset of illness, and eye swabs were
more frequently positive than were throat swabs. Maximum
detection rates were 44% of eye swabs collected on the
second day of illness, and 12% for throat swabs taken on
the second day of illness (figure 2). 39 eye swabs shown to
be positive by RT-PCR were cultured. 31 (79%) of these
yielded infectious A/H7 virus.

Again not sure how much has changed/if it applies to the current situation but assuming "onset of illness" means infected the PCR detection rates seem a bit low.

[AlaskaDenise]

Re: Is H7N9 Spreading from Human to Human in China?

Following the links (at another site of the same paper), I found another paper referencing an updated test with 100% accuracy on wild birds. See:

Analytical Validation of a Real-Time Reverse Transcription Polymerase Chain Reaction Test for Pan-American Lineage H7 Subtype Avian Influenza Viruses

.

[jflorida]

Re: Is H7N9 Spreading from Human to Human in China?

Overall it was around 92 percent under controlled conditions and a small test size. But it does look much better and like you said it appears it can work with most of them. The whole paper:

Analytical validation of a real-time reverse transcription polymerase chain reaction test for
Pan-American lineage H7 subtype Avian influenza viruses [ http://naldc.nal.usda.gov/download/21378/PDF ]

[gsgs]

Re: Is H7N9 Spreading from Human to Human in China?

> The disease is a reassortment - perhaps just recently

molecular clock says > 1year ago

> A relatively mild avian disease with a rapid spread would move much more quickly
> than a pathogenic avian disease that kills off over half the population carrying it to others (i.e. H5N1).

there were subsequent reassortments and changes. It may have become a lethal human
spreader only recently (Chinese new year ?)

[Pathfinder]

Re: Is H7N9 Spreading from Human to Human in China?

Currently no positive samples of H7N9 found in pigs: WHO

English.news.cn 2013-04-09 23:09:35

...
WHO spokesperson Gregory Hartl ...

"At this point, there is no evidence of sustained human to human transmission," he said, adding that there are some "suspected but not yet confirmed cases of perhaps very limited transmission between close family members."

"They are still being investigated," he said.

Hartl told Xinhua one of the suspected family clusters was in Shanghai, with three family members having similar symptoms and one of them being confirmed of H7N9.

The confirmed case died, so has another suspected family member, according to Hartl.

The other suspected family cluster, which included two family members with one of them being confirmed, was in Jiangsu Province, he said.

Hartl said that even if the infection of H7N9 is confirmed in other family member, further investigations are still needed to make sure whether that's a human to human transmission between constant and close contacts or an infection with virus from the same environmental source.

...

http://news.xinhuanet.com/english/health/2013-04/09/c_124559399.htm

[curiosity]

Re: Is H7N9 Spreading from Human to Human in China?

> The disease is a reassortment - perhaps just recently

molecular clock says > 1year ago

> A relatively mild avian disease with a rapid spread would move much more quickly
> than a pathogenic avian disease that kills off over half the population carrying it to others (i.e. H5N1).

there were subsequent reassortments and changes. It may have become a lethal human
spreader only recently (Chinese new year ?)

Are avian hosts infected with an avian influenza virus always a reservoir or are they no longer infectious once they have fought off the infection?

If the fowl are only infectious while they are sick - and not simple "carriers" (like bats with other diseases), the rate of infection as it moves through a flock of susceptible birds would affect the rate of infection in the secondary, exposed, susceptible hosts (humans for example).

If there is a "seasonal" attack rate - say 5% (an arbitrary estimate) among fowl vs. a drifted variant that creates a 20% or more attack rate among fowl, the potential to expose the secondary host increases significantly.

Example: if the avian host's susceptibility is high (i.e. a drifted sequence bypassing last season's antibodies) the epidemic will move faster and through more flocks thereby increasing the geographical spread and amount of potentially infectious exposures. The infections would likewise increase in the secondary host.

Scenario One: Virus was reassorted a year ago (give or take a few days), but genetically drifted (perhaps by altering those very genes that make it suddenly susceptible to humans) to create a larger epidemic in wild birds that in turn increased the amount of exposure to humans.

Scenario Two: Virus was reassorted a year ago (give or take a few days), has remained genetically similar, but was inefficiently spreading among fowl. There were limited human exposures thereby limited opportunities to identify the illness in the occasional "unusual" fatality (people die from unexplained, atypical pneumonias and ARDS all the time - clusters are where investigations begin.) And only now, because the environment is just right, or the population in birds is just right, or any of those other chaotic factors are just right, the virus can move through the fowl efficiently and again - as last scenario - increasing the amount of infections in flocks that in turn increase the amount of exposure to humans.

Of course, still can't rule out H2H or foodborne. They are all hypothetical scenarios that can not be tested until a virus is detected outside of China or it becomes unmanageable and they ask for help from the international community.

There should be some indication ten days after the first poultry culling and market closures that cases are decreasing - IF - domestic poultry are the source.

It would be nice if there was more information on the "retired" population becoming ill. Actually, more epidemiological information on all the cases would be helpful in general.

Is there something to hide? For what possible and sane reason would the Chinese withhold and limit epidemiological information? Even in the interest of controlling "alarming" information - if there are not any epi links and no known H2H - why withold the information?

Informed people are much less scared than uninformed persons creating hypothesis that may or may not be realistic. Or worse, assuming they are not divulging information BECAUSE there is something disastrous happening.

Open up China!

[Pirante]

Re: Is H7N9 Spreading from Human to Human in China?

This is not necessarily related to h2h transmission, but I just had an odd thought about transmissability in general. I've been wondering at the vector for the virus and a recent remark about it being potentially foodborne sparked the idea.

Isn't chicken feet (maybe bird feet in general) um a 'delicacy' there? If these birds are walking around through infected feces then they may themselves not be infected, but be able to carry the infection to other locations. For that matter you may not have to eat the feet at all, they'd just need to perch on something you touch then touch your eyes or mouth with.

For example if pigeons are the reservoir, or one of them, they could poop in an area where chickens walk, and the chickens, while testing un-infected (for a time) would then spread the disease to whoever happen to touch their feet. If the food were improperly prepared, that would only increase the infection risk.

Is this off base? I thought maybe it would do something to explain the odd spread and infection pattern clusters.

[Vibrant62]

Re: Is H7N9 Spreading from Human to Human in China?

Several H5N1 cases originated from preparation of slaughtered birds i.e defeathering, where feathers were found to have a high viral load. Therefore, if it is in poultry birds (ducks, chickens, doves - all of which are eaten) then infection would be most likely to occur during food preparation.

The issue with this is that many of the recorded H7N9 cases are in retirement home residents, so they are unlikely to have been preparing food. Several are recorded as 'not going out at all'. Therefore for a food link to apply, it has to be undercooked infected food IMHO.

[Farmer]

Re: Is H7N9 Spreading from Human to Human in China?

Are avian hosts infected with an avian influenza virus always a reservoir or are they no longer infectious once they have fought off the infection?

If the fowl are only infectious while they are sick - and not simple "carriers" (like bats with other diseases), the rate of infection as it moves through a flock of susceptible birds would affect the rate of infection in the secondary, exposed, susceptible hosts (humans for example).

There is some evidence for short term shedding of influenza virus among experimentally infected asymptomatic ducks:

J Wildl Dis. 2012;48(4):991-8. Intestinal excretion of a wild bird-origin H3N8 low pathogenic avian influenza virus in mallards (Anas Platyrhynchos).
Brown JD, Berghaus RD, Costa TP, Poulson R, Carter DL, Lebarbenchon C, Stallknecht DE.

Abstract
Mallards (Anas platyrhynchos) and other dabbling ducks in the genus Anas are an important component of the wild bird reservoir for avian influenza (AI) virus; these viruses are maintained in migratory duck populations through a fecal-oral transmission route. We provide a detailed characterization of intestinal viral shedding in Mallards infected with a wild bird-origin low pathogenic (LP) AI virus. Five of eight, 1-mo-old Mallards inoculated with a high dose of an H3N8 LP AI virus became infected as determined by reisolation and seroconversion. Infected birds excreted high concentrations of virus for up to 14 days postinoculation (DPI) without exhibiting overt clinical signs of disease. The pattern of viral shedding was relatively consistent between individual birds, with peak shedding on 2-3 DPI and a progressive decline over the remainder of infection. Detection of viral shedding varied depending on sample type (excrement sample or cloacal swab) and diagnostic test (virus isolation or real-time quantitative reverse transcription polymerase chain reaction). Our data provide detailed insights into the intestinal excretion of an H3N8 LP AI virus in Mallards and the performance of diagnostic assays commonly used in wild bird surveillance. Such information is valuable for estimating potential risks for spillover of LP AI viruses from Mallards to domestic animals, developing accurate transmission models for Mallard populations and facilitating the interpretation and comparison of surveillance results from different studies.

http://www.ncbi.nlm.nih.gov/pubmed/23060500

[curiosity]

Re: Is H7N9 Spreading from Human to Human in China?

There is some evidence for short term shedding of influenza virus among experimentally infected asymptomatic ducks:

J Wildl Dis. 2012;48(4):991-8. Intestinal excretion of a wild bird-origin H3N8 low pathogenic avian influenza virus in mallards (Anas Platyrhynchos).
Brown JD, Berghaus RD, Costa TP, Poulson R, Carter DL, Lebarbenchon C, Stallknecht DE.

Abstract
Mallards (Anas platyrhynchos) and other dabbling ducks in the genus Anas are an important component of the wild bird reservoir for avian influenza (AI) virus; these viruses are maintained in migratory duck populations through a fecal-oral transmission route. We provide a detailed characterization of intestinal viral shedding in Mallards infected with a wild bird-origin low pathogenic (LP) AI virus. Five of eight, 1-mo-old Mallards inoculated with a high dose of an H3N8 LP AI virus became infected as determined by reisolation and seroconversion. Infected birds excreted high concentrations of virus for up to 14 days postinoculation (DPI) without exhibiting overt clinical signs of disease. The pattern of viral shedding was relatively consistent between individual birds, with peak shedding on 2-3 DPI and a progressive decline over the remainder of infection. Detection of viral shedding varied depending on sample type (excrement sample or cloacal swab) and diagnostic test (virus isolation or real-time quantitative reverse transcription polymerase chain reaction). Our data provide detailed insights into the intestinal excretion of an H3N8 LP AI virus in Mallards and the performance of diagnostic assays commonly used in wild bird surveillance. Such information is valuable for estimating potential risks for spillover of LP AI viruses from Mallards to domestic animals, developing accurate transmission models for Mallard populations and facilitating the interpretation and comparison of surveillance results from different studies.

http://www.ncbi.nlm.nih.gov/pubmed/23060500

The virus shedding, while longer in some species, still has an average end point? Are there any indications an avian host can merely "carry" the virus continually (over an indescript period of time?), regardless of recent exposure and increasing viral load secondary to infection (albeit asymptomatic?)

[JimO]

Re: Is H7N9 Spreading from Human to Human in China?

Another thing to consider is that often, birds are dunked in scalding water to make it easier to pluck the feathers. This could partially sterilize the carcass during preparation. Also, although many of the confirmed cases are said to have a link to live poultry, there have to be a wide variation in exposure to poultry. I would guess that a large percentage of the population come into "contact" with poultry on a routine basis - walking through a live market, feeding domestic birds in the back yard, feeding pigeons in the park, participating in pigeon racing, etc. But, if this virus is not easily transmitted from bird to human, as many claim, then many of these poultry connections aren't relevent. This brings us back to one of three possibilities:

1) the virus is readilty transmissible from bird to human, but uncommon in poultry.

2) the virus does not transmit efficiently from bird to human, but is widespread in poultry so that a small percentage of poultry contacts results in serious infection without accompanying mild cases.

3) there is a large number of undetected or unreported mild cases resulting in the typical percentage of severe cases and fatalities for influenza (this scenario assumes H2H transmission).

I suppose there are other scenarios, but each of these can explain the number, distribution, and severity we've seen in confirmed cases.

Several H5N1 cases originated from preparation of slaughtered birds i.e defeathering, where feathers were found to have a high viral load. Therefore, if it is in poultry birds (ducks, chickens, doves - all of which are eaten) then infection would be most likely to occur during food preparation.

The issue with this is that many of the recorded H7N9 cases are in retirement home residents, so they are unlikely to have been preparing food. Several are recorded as 'not going out at all'. Therefore for a food link to apply, it has to be undercooked infected food IMHO.