Virology J: Human-like H3N2 Influenza Viruses In Dogs - Guangxi, China

 

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Influenza viruses are constantly evolving, and do so via two well established routes; Antigenic drift & Antigenic Shift (reassortment).

 

Antigenic drift causes small, incremental changes in the virus over time. Drift is the standard evolutionary process of influenza viruses, and often come about due to replication errors that are common with single-strand RNA viruses (see NIAID Video: Antigenic Drift).

 

Shift occurs when one virus swap out chunks of their genetic code with gene segments from another virus.  This is known as reassortment. While far less common than drift, shift can produce abrupt, dramatic, and sometimes pandemic inducing changes to the virus (see NIAID Video: How Influenza Pandemics Occur).

While most reassortant viruses fail to thrive, every once in a while a viable, and competitive new subtype will emerge.  As any virologist will tell you, while rare  – Shift Happens.

 

It has only been in the past few years that dogs have been viewed as potential important `mixing vessels’  for influenza – an evolutionary process that has traditionally been associated with birds and swine. 

 

But as we learn more about the host range (which includes humans, equines, swine, birds, bats, camels, and marine mammals) and the genetic diversity of influenza viruses (currently 18 hemagglutinin & 11 neuraminidase subtypes identified), we find a far more complex and intermingled ecology than previously envisioned. 

 

In years past we’ve looked at a number of species with at least theoretical potential to act as mixing vessels, including in  Mixing Vessels For Influenza & A Host Of Reservoirs.

 

Last summer, and particularly apropos for today’s blog -  in Study: Dogs As Potential `Mixing Vessels’ For Influenza - we looked at the ability of different influenza strains (canine, equine and human)  to infect, and replicate in, canine tracheal tissues. 

Last November, In A Dog & Cat Flu Review, we looked at (among other things) the emergence and evolution of avian H3N2 and equine H3N8 viruses in dogs, and just last week we saw reports that Korea has continued to find evidence of avian H5N8 infection in dogs.

 

So it isn’t a huge surprise that we find a study, published yesterday in the Virology Journal, that has isolated and identified what appears to be a human/swine combination H3N2 influenza virus in pet dogs from Guangxi, China.

 

Emergence of human-like H3N2 influenza viruses in pet dogs in Guangxi, China

Ying Chen^1*, Yan-Ning Mo¹, Hua-Bo Zhou², Zu-Zhang Wei¹, Guo-Jun Wang³, Qing-Xiong Yu¹, Xiong Xiao¹, Wen-Juan Yang¹ and Wei-Jian Huang¹ 

Virology Journal 2015, 12:10  doi:10.1186/s12985-015-0243-2

Published: 3 February 2015

Abstract (provisional)

Background After the 1968 H3N2 pandemic emerged in humans, H3N2 influenza viruses continuously circulated and evolved in nature. An H3N2 variant was circulating in humans in the 1990s and subsequently introduced into the pig population in the 2000s. This virus gradually became the main subtype of swine influenza virus worldwide. However, there were no reports of infections in dogs with this virus.

Findings  In 2013, 35 nasal swabs from pet dogs were positive for Influenza A virus by RT-PCR. Two viruses were isolated and genetically characterized. In the phylogenetic trees of all gene segments, two H3N2 canine isolates clustered with Moscow/10/99 and most H3N2 swine influenza viruses.

These results indicated that two H3N2 CIVs possessed high homology with human/swine influenza viruses, which at the same time exhibited some amino acid substitutions in NA, polymerase basic protein 1 (PB1), and nucleoprotein (NP), which probably were related to the interspecies transmission

.Conclusions These two viruses share the highest homology with swine H3N2, Moscow/99-like viruses, which indicated that these viruses might originate from swine viruses.

The complete article is available as a provisional PDF. The fully formatted PDF and HTML versions are in production.

While it doesn’t appear that these reassortant viruses have become well established in canine hosts, this adds to the growing body of evidence that dogs could serve as intermediate hosts – and potential mixing vessels – for a variety of non-canine influenza viruses.

Swine and poultry undoubtedly pose far larger reassortment risks, simply because they are natural hosts for influenza viruses, are often raised in large numbers and in close proximity with one another, and are often shipped long distances.

 

But as we’ve discussed previously, in China: Avian-Origin Canine H3N2 Prevalence In Farmed Dogs, in some parts of the world dogs are regarded as food  - not pets - and are raised under pretty much the same type of crowded conditions as other livestock, but apparently with even less oversight. 

China’s MOH introduced new regulations in 2013 requiring vaccinations and certificates of health for farmed dogs, but local reporting suggests widespread fraud or blatant disregard for these rules (see Yulin market dog safety not guaranteed - Reporter survey found that no regulations exist blank slaughter procedures).

While likely a minor player, all of this makes dogs a `wild card’ in the evolution and spread of new influenza reassortant viruses, and a host species worth keeping one eye on.

A Plethora Of Pathogens, Even During A Pandemic

Photo Credit CDC Influenza Home Care Guide

 

Keypoints

• New study found H1N1pdm virus among a small minority of samples tested during the opening weeks of the 2009 Pandemic in New South Wales

 

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During the opening days, weeks and months of the 2009 H1N1 pandemic, just about anyone who came down with an influenza-like Illness (ILI) was convinced they had contracted  the dreaded `swine flu’. It was, after all, featured on just about every newscast, some governments were handing out antivirals based on symptoms alone, and there were daily dire warnings about its global spread.

 

But during the pandemic, just as we see during every flu season, influenza isn’t the only respiratory virus in circulation.  That terrible `flu’ you think you had last year? 

Well, it may have been something else, entirely.

 

During the fall of 2009, at the height of the H1N1 pandemic in the United States, I highlighted the following CDC graphic in a blog called ILI’s Aren’t Always The Flu, that showed that 70% of the samples taken from symptomatic patients tested negative for influenza.

 

While we tend to think of influenza as the `severe’ respiratory virus, and all of the others as milder, that isn’t always the case.  Again, during the fall of 2009, we saw reports indicating that a large number of `non-influenza’ severe respiratory infections were treated at Philadelphia’s Children’s Hospital.

 

Thu, Nov. 12, 2009

Tests show fall outbreak is rhinovirus, not swine flu

By Don Sapatkin

Inquirer Staff Writer

(EXCERPT)

Tests at Children's Hospital of Philadelphia suggest that large numbers of people who got sick this fall actually fell victim to a sudden, unusually severe - and continuing - outbreak of rhinovirus, better known as a key cause of the common cold.

Experts say it is logistically and financially impossible to test everyone with flulike symptoms. And signs, treatment, and prognoses for a bad cold and a mild flu are virtually identical, so the response hardly differs.

(Continue . . .)

 

And the same is true every flu season. Common respiratory viruses include metapneumovirus, parainfluenzavirus, respiratory syncytial virus (RSV), adenovirus, or most likely, one of the myriad Rhinoviruses (Common cold).

 

Something that Dr. Ian Mackay has addressed well, and often, in the past.  The following chart comes from his recent blogs on the topic; Respiratory viruses: the viruses we detect in the human respiratory tract:

 

All of which serves as prelude to a new study, conducted in New South Wales, that examines 255 respiratory samples taken during the opening months of the 2009 pandemic, to try to examine exactly what viruses were present.  The results, as you have probably already ascertained, were heavily weighted towards `non-influenza’ viruses.

 

Pandemic clinical case definitions are non-specific: multiple respiratory viruses circulating in the early phases of the 2009 influenza pandemic in New South Wales, Australia

Vigneswary Mala Ratnamohan, Janette Taylor, Frank Zeng, Kenneth McPhie, Christopher C Blyth, Sheena Adamson, Jen Kok and Dominic E Dwyer

Virology Journal 2014, 11:113  doi:10.1186/1743-422X-11-113

Published: 18 June 2014

Abstract (provisional)

Background

During the early phases of the 2009 pandemic, subjects with influenza-like illness only had laboratory testing specific for the new A(H1N1)pdm09 virus.

Findings: Between 25th May and 7th June 2009, during the pandemic CONTAIN phase, A(H1N1)pdm09 virus was detected using nucleic acid tests in only 56 of 1466 (3.8%) samples meeting the clinical case definition required for A(H1N1)pdm09 testing. Two hundred and fifty-five randomly selected A(H1N1)pdm09 virus-negative samples were tested for other respiratory viruses using a real-time multiplex PCR assay. Of the 255 samples tested, 113 (44.3%) had other respiratory viruses detected: rhinoviruses 63.7%, seasonal influenza A 17.6%, respiratory syncytial virus 7.9%, human metapneumovirus 5.3%, parainfluenzaviruses 4.4%, influenza B virus 4.4%, and enteroviruses 0.8%. Viral co-infections were present in 4.3% of samples.

Conclusions

In the very early stages of a new pandemic, limiting testing to only the novel virus will miss other clinically important co-circulating respiratory pathogens.

 

The entire study is available as a PDF at this link.    I’ve excerpted the last two paragraphs from the study below:

 

Even  prior  to  the  widespread  transmission  of  A(H1N1)pdm09  virus  in  Australia,  limiting testing to travellers did not improve the specificity of testing. Furthermore, if laboratories use NAT  to  determine  other  causes  of  infection,  testing  capacity  in  an  outbreak  may  soon  be reached. However, when the causative pathogen of an outbreak has been  identified and the outbreak  has  progressed  beyond  containment,  then  the  testing  algorithms  need  revision  to target  only  specific  indications,  such  as  a  location  of  new  or  significant  clusters,  or  for individuals at risk of severe disease.

In  conclusion,  laboratory  testing  specifically  targeting  only  the  new  virus  will  miss  other clinically  important  co-circulating  respiratory  pathogens  in  the  very  early  stages  of  a pandemic. Detecting the presence of other viruses may provide important information on the impact of pre-existing viruses when a new pandemic virus is circulating.

 

 

It should be noted that the 2009 H1N1 pandemic began when the northern hemisphere’s flu season was coming to an end, and the southern hemisphere’s flu season was just getting started.

 

One can’t automatically assume that the same sorts of ratios would have prevailed in regions where other viruses were circulating less frequently. Interestingly, the rate of H1N1pdm positive tests may very well have been dampened in the Southern Hemisphere by the co-circulation of some of these other viruses. 

 

A topic that Ian Mackay explored earlier this week in  Influenza in Queensland, Australia: 1-Jan (Week 1) to 8-June (Week 23); the idea that the body’s immune response to one viral infection may temporarily protect you against infection from another. 

 

And an idea similar to one we looked at back in 2010 in  Eurosurveillance: The Temporary Immunity Hypothesis  (and again, in 2012 in EID Journal: Revisiting The `Canadian Problem’.

Study: Inactivation Of A/H7N9 By Temperature, UV, pH, and Disinfectants

 

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While we’ve heard very little regarding the H7N9 avian flu virus over the past four months, many experts worry that status could change as cooler temperature arrive this fall. So over the summer we’ve watched as a small parade of studies on this emerging virus have been published that have looked at everything from its susceptibility to antivirals, transmissibility in ferrets and mice, to its ability to bind to mammalian receptor cells.

 

Today, we’ve another study, this time looking at the effectiveness of common disinfection techniques in inactivating the H7N9 virus.

 

You may recall that 4 1/2  years ago, in Study: (H5N1): Effects Of Physico-Chemical Factors On Its Survival we looked at similar research done on the  H5N1 virus. Should any pandemic virus begin to spread, the ability to disinfect hospital rooms, ambulances, medical equipment .  .  and yes - even sick rooms in private residences – becomes an important issue. 

 

Today’s open access study appears in the Virology Journal, and may be viewed in its entirety at the link below:

 

Inactivation of the novel avian influenza A (H7N9) virus under physical conditions or chemical agents treatment

Shumei Zou, Junfeng Guo, Rongbao Gao, Libo Dong, Jianfang Zhou, Ye Zhang, Jie Dong, Hong Bo, Kun Qin and Yuelong Shu

Virology Journal 2013, 10:289 doi:10.1186/1743-422X-10-289

Published: 15 September 2013

ABSTACT (Excerpts)

Methods

To determine the inactivation effectiveness of the novel avian influenza A (H7N9) virus under various physical conditions and chemical treatments, two H7N9 viruses A/Anhui/1/2013 and A/Shanghai/1/2013 were treated by varied temperatures, ultraviolet light, varied pHs and different disinfectants. The viruses with107.7 EID50 were exposed to physical conditions (temperature, ultraviolet light and pH) or treated with commercial chemical agents (Sodium Hypochlorite, Virkon(R)-S, and Ethanol) respectively. After these treatments, the viruses were inoculated in SPF embryonated chicken eggs, the allantoic fluid was collected after 72--96 hours culture at 35[degree sign]C and tested by haemagglutination assay.

Results

Both of the tested viruses could tolerate conditions under 56[degree sign]C for 15 minutes or 60[degree sign]C for 5 minutes, but their infectivity was completely lost under 56[degree sign]C for 30 minutes, 65[degree sign]C for 10 minutes, 70[degree sign]C,75[degree sign]C and 100[degree sign]C for 1 minute. It was also observed that the H7N9 viruses lost their infectivity totally after exposure of ultraviolet light irradiation for 30 minutes or longer time. Additionally, the viruses were completely inactivated at pH less than 2 for 0.5 hour or pH 3 for 24 hours, however, viruses remained infectious under pH treatment of 4--12 for 24 hours. The viruses were totally disinfected when treated with Sodium Hypochlorite, Virkon(R)-S and Ethanol at recommended concentrations after only 5minutes.

Conclusions

The novel avian influenza A (H7N9) virus can be inactivated under some physical conditions or with chemical treatments, but they present high tolerance to moderately acidic or higher alkali conditions. The results provided the essential information for public health intervention of novel H7N9 avian influenza outbreak.

(Continue . . . )

 

 

Like it’s H5 avian cousin, H7N9 is susceptible to heat (70C > 1 min), prolonged UV exposure (30 mins), strong acids and alkalis, and the usual disinfectants like bleach (Sodium Hypochlorite), alcohol (75%), and Virkon ®-S when applied at their recommended concentrations and for the recommended length of time (usually 5 minutes).

 

H7N9 appears unusually tolerant of moderate acids and alkalis', maintaining its infectivity under pH 4–12 conditions  for 24 hours, or under pH 3 conditions for 30 minutes.  To illustrate of the relative acidity and alkalinity of various common substances, I’ve reproduced the following chart from  Wikipedia.

 

By comparison, the 2009 study (Avian influenza virus (H5N1); effects of physico-chemical factors on its survival) found the H5N1 subtype was a less tolerant of its environmental pH – losing its viability when exposed to pH 1, 3, 11 and 13 after 6 hours, and was inactivated at pH 5 after 24 hours.

 

I’ve reproduced  today’s study conclusion below:

 

Conclusion

The results indicated that the novel avian influenza H7N9 viruses can  be completely inactivated using high temperature (e.g. 56°C or above),UV light irradiation,and commercial disinfectants (Sodium Hypochlorite, Virkon®-S and Ethanol). But the virus presents a high tolerance to moderately acidic or higher alkali conditions. The present results would provide essential information for public health intervention of novel avian influenza H7N9 outbreaks.

 

Perhaps the biggest takeaway message here is that while disinfection of surfaces using standard techniques will work, attention must be paid to disinfectant concentrations and to (disinfectant, heat, UV) exposure times. Tasks that housecleaning personnel in hospitals are quite familiar with.

 

On the other hand, the kind of cursory cleaning one might do in one’s home, or that might be done by a cleaning  staff at a motel, hotel, restaurant, or at work  (ie. giving a surface a quick wipe down with a household cleaner/disinfectant)  might not be sufficient to kill the virus.

Something to consider during every cold & flu season, not just when a novel virus threatens.

 

And an excellent reason to remember to practice good flu hygiene (frequent hand washing/sanitizing, avoid touching your face, covering coughs & sneezes, and staying home if you are sick) all year round.