Webster, Peris, & Guan: H5N1 Influenza Continues to Circulate and C

[wetDirt]

http://www.asm.org/microbe/index.asp?bid=47152

Summary

• Highly pathogenic variants of H5N1 influenza virus that moved from Asia to India, Europe, and Africa have continued to evolve in Southeast China, giving rise to novel variants and raising concerns that these viruses will spread elsewhere and become endemic in wild birds throughout the world.

• More than half of the 250 persons infected so far with H5N1 died, and efforts to control the spread of this virus led to culling of more than 200 million domestic birds in Asia.

• The H5N1 viruses are overturning several concepts about how influenza viruses behave, including ideas about what species of birds safely transmit them and which bird species the viruses can sicken and kill; several species of cat can be infected with and transmit H5N1.

• Once a particular influenza virus becomes widespread among bird species within a region, control measures that depend on culling of flocks need to be augmented with vaccine use.

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A nice summary article with lots of interesting little tidbits:

These viruses kill more than 50% of humans that they infect. One such virus infected a family cluster of eight persons in Indonesia, and included three sequential human-to-human transmissions. Fortunately, however, that particular cluster did not expand. Moreover, in humans, the H5N1 viruses remain poorly transmissible between individuals. In over 40 years of experience with influenza, the Asian H5N1 is the most virulent virus I have encountered (R.G.W.); if it does acquire consistent human-to-human transmissibility— it will likely be catastrophic.

 

[cartski]

Re: Webster, Peris, & Guan: H5N1 Influenza Continues to Circulate and C

This is an excellent artcicle, IMO!

J.

 

[Mellie]

Re: Webster, Peris, & Guan: H5N1 Influenza Continues to Circulate and C

One interesting portion in an interesting article:

<div style="margin: 5px 20px 20px;"> Quote:
<table cellpadding="6" cellspacing="0" border="0" width="100%"> <tbody><tr> <td class="alt2" style="border: 1px inset ;"> Stability and Environmental Sources of Influenza Viruses
(snip)

Investigators formerly believed that influenza viruses are transmitted unidirectionally from wild migratory birds to domestic species. However, <b>the A/BH Goose/Qinghai/65/05 (H5N1) virus is a reassortant that obtained its M, NS, PA, PB1, and PB2 gene segments from A/Mallard duck/Jiangxi/1653/05 (H5N1) and it

 

[JJackson]

Re: Webster, Peris, & Guan: H5N1 Influenza Continues to Circulate and C

Sure is great to have something that points to sequences that could be evaluated using recombination to see if that mechanism is a better "fit" than recombination.

Reassortment?

 

[Mellie]

Re: Webster, Peris, & Guan: H5N1 Influenza Continues to Circulate and C

Yep, typo: em I had a phone call and it disrupted my train of thought!

 

[Mellie]

Re: Webster, Peris, & Guan: H5N1 Influenza Continues to Circulate and C

(Repost of above. Sometimes editing something chops it off.)

One interesting portion in an interesting article:

Quote:
<table cellpadding="6" cellspacing="0" border="0" width="100%"> <tbody><tr> <td class="alt2" style="border: 1px inset ;"> Stability and Environmental Sources of Influenza Viruses
(snip)

Investigators formerly believed that influenza viruses are transmitted unidirectionally from wild migratory birds to domestic species. However, the A/BH Goose/Qinghai/65/05 (H5N1) virus is a reassortant that obtained its M, NS, PA, PB1, and PB2 gene segments from A/Mallard duck/Jiangxi/1653/05 (H5N1) and it?s HA, NA, and NP segments from A/Mallard duck/Jiangxi/ 2136/05 (H5N1). In both cases, domestic ducks infected mallards that were over-wintering in southern China.

Thus, the A/BH Goose/Qinghai/65/05 (H5N1) virus apparently contains gene segments from influenza viruses in domestic birds, along with gene segments that were spread in part by migratory birds. The A/BH Goose/Qinghai/65/05 (H5N1) virus contains lysine at residue 627 of PB2, which is associated with pathogenicity in mammals. Did the selection of the PB2 lysine 627 variant occur in mammals in China?

Since 2001, investigators report finding H5N1 infecting passerine birds, some of which were killed during the 2002?2003 outbreak in Hong Kong. Similarly, H5N1 viruses were isolated from dead crows near affected chicken farms in Japan. Early in 2006, H5N1 influenza viruses were isolated from dead crested mynahs, common magpies, oriental magpie robins, and Japanese white-eyes in the New Territories of Hong Kong. At times, passerine birds seemed to be falling from the sky. These events received limited attention perhaps because they were taken to reflect infections in domestic poultry rather than establishment of H5N1 viruses in wild passerine populations. Although infections in domestic poultry were the probable source of these H5N1 viruses, passerine birds doubtless contribute to the spread of H5N1 viruses in nearby domestic poultry flocks and among cats. </td> </tr> </tbody></table>
Is there an alternative explanation for the bold portion using recombination as the mechanism?

I think it's important to point out that this article is a summary. That does not reduce its value, however, but makes it tend toward being more of an "opinion piece". It does not point to original research as it makes its points. I'd like to see some of the original research or at least see if there are alternative explanations for the "reassortment" findings.

Sure is great to have something that points to sequences that could be evaluated using recombination to see if that mechanism is a better "fit" than reassortment.

 

[4-ABBA]

Re: Webster, Peris, & Guan: H5N1 Influenza Continues to Circulate and C

The article says H5N1 is in India. I did not know the Indian govt ever acknowledged this...

 

[4-ABBA]

Re: Webster, Peris, & Guan: H5N1 Influenza Continues to Circulate and C

This is an excellent artcicle, IMO!

J.

This quote from the article is astonishing!

"The newer viruses appear to spread readily as aerosols among birds, unlike influenza viruses that circulated in mallard ducks, for example, before 2002 (Fig. 2). Thus, based on 23 different H5N1 viruses in mallard ducks, the amount of virus excreted orally increased by a factor of 10 after 2002."

Is this a portent on possible future H5N1 manifestation in humans?

 

[Mamabird]

Re: Webster, Peris, & Guan: H5N1 Influenza Continues to Circulate and C

I believe the reassortment evidence you seek is in the three genetic sequences given by the authors:

A/barheaded goose/Qinghai/65/05,

A/mallard duck/Jiangxi/1653/05, and

A/mallard duck/Jiangxi/2136/05.

A comparison of the eight gene segments and the eleven proteins reveals that the Jiangxi isolates 1653 and 2136 are significantly different from one another, and that the Qinghai isolate is almost an exact match of the two Jiangxi's at the protein levels identified. Since Qinghai is the later isolate, it could not be the source of mallard duck infections. Therefore, pretty clear indication that we have domestic fowl infecting wild fowl, and that the mechanism of reassortment is also at play.