UKHSA Confirms 4th Clade Ib Mpox Case In Household Cluster

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The  clade Ib Mpox virus which emerged last year in the DRC is reportedly more virulent, and potentially more transmissible, than the clade II mpox virus which began its world tour in the spring of 2022.  

For that reason, it has been designated a high consequence infectious disease (HCID) in the UK, and its recent spread outside of Africa (to Sweden, India, Germany, and Thailand) has raised alarm bells. 

Last week the UK became the 5th non-African nation to report an imported case in a traveler recently returned from Africa.  On Monday, we learned that 2 of this patient's housemates had been infected. Today the UK's Health Security Agency has announced a third member of that household is receiving medical treatment for the infection.

The UK Health Security Agency (UKHSA) confirms additional cases of Clade Ib mpox.

From:UK Health Security Agenc yLast updated 6 November 2024 — See all updates

One further case of Clade Ib mpox has been detected in a household contact of the first case, the UK Health Security Agency (UKSHA) can confirm.

This brings the total number of confirmed cases to 4, all of which belong to the same household.

The patient is currently under specialist care at Guy’s and St Thomas’ NHS Foundation Trust in London. The risk to the UK population remains low.

The patient has been isolating since identified as a contact of the first case and no additional contact tracing is required.

Professor Susan Hopkins, Chief Medical Adviser at UKHSA, said:

Mpox is very infectious in households with close contact and so it is not unexpected to see further cases within the same household.

The overall risk to the UK population remains low. We are working with partners to make sure all contacts of the cases are identified and contacted to reduce the risk of further spread.

Contacts of cases are being followed up by UKHSA and partner organisations. All contacts will be offered testing and vaccination as needed and advised on any necessary further care if they have symptoms or test positive. 

There has been extensive planning underway to ensure healthcare professionals are equipped and prepared to respond to any further confirmed cases.organisations. All contacts will be offered testing and vaccination as needed and advised on any necessary further care if they have symptoms or test positive.

There has been extensive planning underway to ensure healthcare professionals are equipped and prepared to respond to any further confirmed cases.

Preprint: Emergence of a Novel Reassortant Clade 2.3.2.1c Avian Influenza A/H5N1 Virus Associated with Human Cases in Cambodia

 

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After going nearly a decade without reporting a human infection, Cambodia reported the first of 16 recent infections in February of 2023 (see graphic above), with nearly a 40% fatality rate (see WHO Update On Cambodian H5N1 Cases).  

As we've often seen with H5N1, children and adolescents were the hardest hit.

While Cambodia's avian flu resurgence came from an older (2.3.2.1c) clade of H5N1, last April in - FAO Statement On Reassortment Between H5N1 Clade 2.3.4.4b & Clade 2.3.2.1c Viruses In Mekong Delta Region - we learned that a new genotype - made up of this older clade and the newer 2.3.4.4b clade of H5N1 - had emerged in Southeast Asia.

The FAO wrote:

In Asia, several clades continue to circulate, including A(H5N1) 2.3.4.4b, 2.3.2.1c and others, which can lead to reassortment and the appearance of viruses with new characteristics. A novel reassortant influenza A(H5N1) virus has been detected across the Greater Mekong Subregion (GMS), causing infections in both humans and poultry since mid- 2022.

This virus has recently caused human outbreaks in Cambodia early this year. This virus contains the surface proteins from clade 2.3.2.1c that has circulated locally, but internal genes from a more recent clade 2.3.4.4b virus.

The introduction and widespread circulation of this reassortant influenza A(H5N1) virus into the GMS poses a significant risk to both animal and human health, given the historical impact of HPAI outbreaks in the region. Further, this reassortment event indicates not only the adaptive capacity of the virus but also the ever-present risk of the emergence of new, potentially more virulent strains.

Although these reports indicated that humans and poultry had been infected by this new genotype, details on its emergence were scant.  Today we have a preprint which seeks to fill in some of those gaps. 

I've only posted the link, abstract, and some excerpts, so follow the link to read it in its entirety.

Emergence of a Novel Reassortant Clade 2.3.2.1c Avian Influenza A/H5N1 Virus Associated with Human Cases in Cambodia
Jurre Y Siegers, Ruopeng Xie, Alexander M P Byrne, Kimberly M Edwards, Shu Hu, Sokhoun Yann, Sarath Sin, Songha Tok, Kimlay Chea, Srey Viseth Horm, Chenthearath Rith, Seangmai Keo, Leakhena Pum, Veasna Duong, Heidi Auerswald, Yisuong Phou, Sonita Kol, Andre Spiegel, Ruth Harvey, Sothyra Tum, San Sorn, Bunnary Seng, Yi Sengdoeurn, Darapheak Chau, Savuth Chin, Makara Hak, Vanra Ieng, Sarika Patel, Han Di, Charles Todd Davis, Alyssa Finlay, Borann Sar, Peter M Thielen, Filip F Claes, Nicola S Lewis, Sovann Ly, Vijaykrishna Dhanasekaran, Erik A Karlsson
doi: https://doi.org/10.1101/2024.11.04.24313747 

     Download PDF 

Abstract

After nearly a decade without reported human A/H5N1 infections, Cambodia faced a sudden resurgence with 16 cases between February 2023 and August 2024, all caused by A/H5 clade 2.3.2.1c viruses. Fourteen cases involved a novel reassortant A/H5N1 virus with gene segments from both clade 2.3.2.1c and clade 2.3.4.4b viruses. The emergence of this novel genotype underscores the persistent and ongoing threat of avian influenza in Southeast Asia. This study details the timeline and genomic epidemiology of these infections and related poultry outbreaks in Cambodia.

          (SNIP)

Phylogenetic analyses of each of the gene segments revealed that A/H5N1 viruses in Cambodia,detected from October 2023 onwards in both humans and poultry, represent a novel genotype resulting from reassortment. This reassortment combines segments from clade 2.3.2.1c (HA, NP, and NA) and clade 2.3.4.4b (PB2, PB1, PA, MP, and NS) viruses (Figure 2). In Cambodia, this novel 2.3.2.1c genotype has completely replaced the endemic 2.3.2.1c genotype that has dominated in poultry for the last decade.

(SNIP)

While the phenotypic contributions of newly introduced clade 2.3.4.4b internal gene segments have yet to be elucidated, the presence of amino acid mutations in both human and poultry viruses such as E627K in the 2.3.4.4b-origin PB2 gene segment suggests enhanced capacity for mammalian infection.

To better understand the zoonotic risk that these viruses pose, further risk assessment in silico, ex vivo, in vivo, and in vitro is critical. In addition, the detection of the PB2 627K mutation in poultry is also a concern, as it may become established in widespread circulation.

(SNIP)

In conclusion, these recurrent zoonotic infections caused by a novel reassortant A/H5N1 viruses in Cambodia serve as a reminder of the ever-present threat of AIV to global health security. Despite the recent focus on global dissemination and expanded host range of clade 2.3.4.4b 45-47 341 , clade 2.3.2.1c viruses remain a significant concern, particularly in Asia, where the two clades co-circulate.

A coordinated, regional approach is essential for effectively monitoring the threat of AIV and ensuring  preparedness and response to emerging viral threats. Indeed, this study underscores the critical need and effectiveness of a unified, One Health approach to combat the evolving landscape of AIV. The urgency of this collaborative effort cannot be overstated as these viruses continue to adapt and reassort, increasing the risk of a strain evolving the capacity for efficient human-to-human transmission. 

To stay ahead of this threat, we must prioritize sustainable funding for long-term surveillance, enhance laboratory capacity for rapid whole genome sequencing, and foster open, trust based information sharing across borders. Our collective preparedness today will determine our ability to protect global health tomorrow.

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As we discussed in my last blog (see UK: HPAI H5N5 Rising), the threat from HPAI H5 comes from a large and growing array of related viruses, all of which are on their own evolutionary pathway, and any of which could become a global health threat. 

Even if we get lucky, and H5 doesn't have what it takes to spark a pandemic, there's no lack of other contenders in the wild.  Whether from an influenza virus, a coronavirus, `Disease X', another pandemic is inevitable. 

Which is why, in 2021's PNAS Research: Intensity and Frequency of Extreme Novel Epidemics, researchers estimated our pandemic risk may increase 3-fold over the next few decades. 

UK: HPAI H5N5 Rising

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Although the spillover of HPAI H5N1 into mammals has most of our attention, H5 influenza continues to evolve, and over the years has produced dozens of clades and subclades, hundreds of genotypes, spanning  9 different subtypes (H5N1-H5N9).  

Many have failed to thrive, or gone extinct, but new variations continue to appear. 

While China's H5N6 virus is arguably the most concerning of these offshoots, we've also been following the spread of HPAI H5N5 in Europe - and its crossing over into Canada - with considerable interest. 

We've seen reports of H5N5 in European birds going back to 2016, but it was detected in dead raccoons on Prince Edward Island about 18 months ago (see CIDRAP Report Canada reports first H5N5 avian flu in a mammal). 

We looked in again last April with HPAI H5N5: A Variation On A Theme, and again in May with WAHIS: More Reports of HPAI H5N5 in Canada. 

Last July, in Cell Reports: Multiple Transatlantic Incursions of HPAI clade 2.3.4.4b A(H5N5) Virus into North America and Spillover to Mammals, researchers reported finding the mammalian adaptive E627K mutation in a number of samples. They wrote:

Thus, while A(H5N5) viruses are comparably uncommon, their high virulence and mortality potential demand global surveillance and further studies to untangle the molecular markers influencing virulence, transmission, adaptability, and host susceptibility.

The UK, which last reported an outbreak of HPAI in poultry last February, yesterday published 3 avian flu related documents in rapid succession. 

The first being an Updated Outbreak Assessment #4 High pathogenicity avian influenza (HPAI) in Great Britain and Europe, dated October 30th, which stated:

Since our previous outbreak assessment on 7 October 2024, there have been no new reports of high pathogenicity avian influenza (HPAI) H5 clade 2.3.3.4b in domestic poultry in Great Britain (England, Scotland and Wales). There have, however, been 15 more HPAI H5 clade 2.3.3.4b events involving 26 “found-dead” wild birds in Great Britain. Of these, 25 were HPAI H5N5 with 1 case of HPAI H5N1.

Second, a Bird flu (avian influenza): latest situation in England update which stated, based on the recent findings in wild birds, that the `. . . risk level of HPAI H5 in wild birds has increased from medium to high.'

5 November 2024

All bird keepers are urged to remain vigilant and take action to protect their birds following a further increase in the avian influenza (‘bird flu’) risk levels in Great Britain.

Highly pathogenic avian influenza (HPAI) H5N5 and H5N1 have been detected in wild birds in Great Britain this autumn.

The risk level of HPAI H5 in wild birds has increased from medium to high.

The risk level in poultry:

• where good biosecurity is consistently applied at all times has increased from very low to low with low uncertainty
• where there is suboptimal or poor biosecurity remains assessed as low but is heightened with high uncertainty

While findings of HPAI in wild birds during recent years have been dominated by the H5N1 virus strain, the finding of HPAI H5N5 was likely this season and follows previous findings in Great Britain and recent detections of the strain in continental Europe.

And lastly, overnight, Defra announced the detection of HPAI H5N5 at a poultry farm in Yorkshire.

Further update 5 November 2024

Highly pathogenic avian influenza (HPAI) H5N5 has been confirmed in commercial poultry at a premises near Hornsea, East Riding of Yorkshire, Yorkshire. All poultry on the infected premises will be humanely culled. A 3km protection zone and 10km surveillance zone has been put in place surrounding the premises.

Check if you’re in a bird flu disease zone on the map.

If you’re in a bird flu disease control zone you must follow the rules for that zone and check if you need a licence to move poultry, poultry by-products, eggs, material or mammals.

In line with World Organisation for Animal Health (WOAH) rules, this means Great Britain is no longer free from highly pathogenic avian influenza. Northern Ireland continues to have self-declared zonal freedom from highly pathogenic avian influenza.

Practicing good biosecurity at all times protects the health and welfare of your birds and for commercial keepers will help protect your business from HPAI and other diseases.

While it isn't clear how much of a player H5N5 will become, it has been increasingly reported across Europe, has crossed the Atlantic several times, and Ferrets inoculated with A(H5N5) viruses showed rapid, severe disease onset, with some evidence of direct contact transmission.

Credit Cell Reports July 2024

Given HPAI H5's track record, this is an avian flu variant we need to keep an eye on. 

Review Article - Influenza A Viruses in the Swine Population: Ecology and Geographical Distribution

CREDIT CDC

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Given the news last week that a pig in Oregon tested positive for the H5N1 virus, the following review article - recently published in the Journal Viruses on the ecology and distribution of influenza A viruses in swine - is especially timely.   

Swine (and Equines) are the only hosts known to be susceptible to all 4 types of influenza (A, B, C & D), and reassortment in swine has been linked to the generation of previous pandemic viruses. 

Of the CDC's IRAT (Influenza Risk Assessment Tool) list of 25 zoonotic influenza A viruses with pandemic potential, 4 are swine variant viruses and the virus with the highest emergence & impact score is a Swine Variant H1N1 from China.

Although the following review covers a lot of ground, it mentions the H5N1 virus 11 times, and `avian' flu viruses more than 50 times.  Anyone looking for a comprehensive review of influenza A viruses in swine will find it very much worth reading.

Due to its length, I've only posted some excerpts.  Follow the link to read it in its entirety. 

Influenza A Viruses in the Swine Population: Ecology and Geographical Distribution
by
Nailya Klivleyeva 1, Nurbol Saktaganov 1, Tatyana Glebova 1,*, Galina Lukmanova 1, Nuray Ongarbayeva 1 and Richard Webby 2

Viruses 2024, 16(11), 1728; https://doi.org/10.3390/v16111728
Submission received: 27 September 2024 / Published: 1 November 2024

Abstract

Despite the efforts of practical medicine and virology, influenza viruses remain the most important pathogens affecting human and animal health. Swine are exposed to infection with all types of influenza A, B, C, and D viruses. Influenza viruses have low pathogenicity for swine, but in the case of co-infection with other pathogens, the outcome can be much more serious, even fatal. Having a high zoonotic potential, swine play an important role in the ecology and spread of influenza to humans.

In this study, we review the state of the scientific literature on the zoonotic spread of swine influenza A viruses among humans, their circulation in swine populations worldwide, reverse zoonosis from humans to swine, and their role in interspecies transmission. The analysis covers a long period to trace the ecology and evolutionary history of influenza A viruses in swine.

The following databases were used to search the literature: Scopus, Web of Science, Google Scholar, and PubMed. In this review, 314 papers are considered: n = 107 from Asia, n = 93 from the U.S., n = 86 from Europe, n = 20 from Africa, and n = 8 from Australia. According to the date of publication, they are conditionally divided into three groups: contemporary, released from 2011 to the present (n = 121); 2000–2010 (n = 108); and 1919–1999 (n = 85).

1. Introduction

Influenza viruses (IVs) belong to the Orthomyxoviridae family and have a segmented genome with single-stranded, negative-sense RNA. Based on genetic and antigenic differences, IVs are divided into four genera, A, B, C, and D, which infect different species of mammals and birds with the four types of IV that occur in swine [1,2,3,4]. Among the four types of IVs, influenza A viruses (IAVs) are highly significant pathogens responsible for serious epidemics in humans and domestic animals. Figure 1 presents different species of animals infected with the four types of IVs.

Figure 1. Influenza A, B, C, and D in different species of mammals.

The IAV genome consists of eight RNA segments: PB2, PB1, PA, hemagglutinin (HA), NP, neuraminidase (NA), M, and NS [1]. Two surface antigens, HA and NA, are mainly subject to antigenic variability, while internal proteins (NP and M) are relatively conservative. HA and NA play an essential role in the initial stages of cell infection [5]. HA binds to host cell receptors that contain terminal sialic acid residues (-2,6-SA or -2,3-SA). The HA gene is in charge of attaching viral pieces to the host cell receptor. NA removes the cell surface receptor (sialic acid); this is crucial for releasing viral particles from the cell surface and virus spillover [5].

Based on major antigenic differences in surface proteins (HA and NA), 18 HA subtypes (H1–H18) and 11 NA subtypes (N1–N11) have been identified. The H1–H16 and N1–N9 virus subtypes have been identified in waterfowl, which are believed to constitute the natural IAV reservoir [6,7,8], while the H17–H18 and N10–N11 subtype sequences have been found in bats [9,10,11]. Only a limited number of subtypes have been found in mammals, such as H1 and H3 viral subtypes, which we identified and circulate in both humans and swine [12,13,14,15,16,17,18,19]. Figure 2 presents subtypes of H1–H18 hemagglutinins and N1–N11 neuraminidases of influenza viruses in different species of mammals.

Figure 2. Influenza subtypes of viruses H1–H18 and N1–N11 in different species of mammals.

IAVs’ epidemiology and ecology are complicated by their multi-host and segmented genome. IAVs are among the main pathogens in swine that give rise to acute respiratory infections and cause significant economic losses for swine farms. 

In addition to swine IAVs, human and avian IAVs can also infect swine. Swine are believed to serve as an intermediate “mixing vessel” for generating a variety of novel IVs [20]. The co-infection of swine with two or more IAV strains can induce reassortment [21,22], which in turn can promote the emergence of new IV strains [23,24,25]. There are numerous reports of zoonotic infections in humans with swine IAVs and reverse zoonotic infections in swine with human IAVs [26,27,28,29,30].

          (SNIP)

5. Conclusions

Swine play an important role in the formation of present-day influenza ecology. Swine have specific receptors for avian, porcine, and human IAV in the tracheal epithelium, which may contribute to the emergence of new reassortant variants that could potentially pose a public health threat [8,249,303]. The complex interaction of IAVs of human, avian, and porcine evolutionary origin in swine is supported by the detection of multiple IAV subtypes in swine populations, including H1, H2, H3, H4, H5, H7, and H9 [304]. Swine play an important role in the epidemiology of IV, which is dangerous to humans [305]. For example, influenza A(H1N1)pdm09 is thought to have been present in swine herds for several months before it became a pandemic strain in humans [35].

Human-to-swine transmission of IV occurs much more frequently than swine-to-human transmission [30]. Despite the genetic diversity of SIVs found in the swine population, only H1 and H3 IAVs formed stable lineages similar to human IVs. The nature of H1 and H3 viruses nevertheless differs between the two host populations. In addition, the distribution of subtypes and genotypes of endemic IAVs varies greatly by geographic region due to the repeated introduction of avian and human influenza viruses. An exception is H1N1pdm09, which is mainly widespread due to multiple human-to-swine reintroductions [57,102,167,176,306,307,308,309,310,311,312]. New cases of infection with avian influenza H5N1 virus have been confirmed in dairy cattle and pigs [313,314]. However, no information has been found on the presence of swine-origin IVs in dairy cows.

The continuous monitoring and genome-wide genetic characterization of SIVs make it possible to obtain a complete picture of the infectious disease process, predict the epidemiological and epizootic situation, and choose the right strategy and tactics for preventive and anti-epidemic measures. Understanding the transmission modes is of decisive importance for developing effective control strategies and making reasonable surveillance recommendations.

This study may provide the information needed to develop a more effective method for monitoring SIVs and selecting countermeasures to prevent interspecies transmission, which could become a potential pre-pandemic situation.

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CDC H5 Updates: Current Situation & Response (Nov 4th)

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Late yesterday the CDC published two updates (here and here) on the current situation of H5 in the United States and their ongoing response.  There are some differences between the number of human cases confirmed by the CDC (n=44) and what has been reported by states (at least 48), but both numbers continue to rise. 

The CDC explains:

The 44 cases include 20 cases in dairy farm workers in California, three of which were confirmed by CDC last week and three on Monday, November 4; nine cases in poultry farm workers in Washington state, three of which were confirmed by CDC last week; and one case associated with the Washington poultry outbreak that was confirmed by CDC last week and is pending jurisdiction assignment. Not included in that count are four probable cases -- one in a California dairy farm worker and three in Washington state poultry farm workers. While these probable cases were negative on confirmatory testing at CDC, all four met the Council of State and Territorial Epidemiologists (CSTE) probable case definition and have been reported by the states.

While it would be nice to have agreement, the reality is both numbers are likely significant undercounts. 

We've seen anecdotal reports of symptomatic farm workers who refused testing (see EID Journal: Avian Influenza A(H5N1) Virus among Dairy Cattle, Texas, USA), and our influenza surveillance systems are unlikely to pick up non-hospitalized cases. 

In their weekly laboratory update, the CDC reports:

Laboratory Update

CDC posted a spotlight describing the results of CDC's first study investigating the effects in ferrets of an avian influenza A(H5N1) virus isolated from a human case in the United States. The study, published on October 28 in the journal Nature, found that when 12 laboratory ferrets were infected with a virus isolated from a human case in Texas (A/Texas/37/2024), all 12 experienced severe and fatal disease. The study also found that this virus efficiently transmitted from infected ferrets to healthy ferrets in the presence of direct contact and, less efficiently, via fomites and respiratory droplets. Preliminary findings from this study, first shared in June 2024, were instrumental in informing early risk assessments related to this outbreak.

To date, CDC has confirmed nine human cases of H5 bird flu i,n poultry farm workers in Washington state. Genetic sequencing of three of these cases confirms that all are avian influenza A(H5N1) viruses from clade 2.3.4.4b and that all are closely related genetically to the viruses causing infections in poultry on the farm where depopulation was conducted. CDC has successfully obtained partial gene sequences for viruses from three cases in Washington (A/Washington/239/2024, A/Washington/240/2024, A/Washington/247/2024) with other cases pending sequence analysis.

That sequencing information showed that the viruses' hemagglutinin (HA) is closely related to candidate vaccine viruses (CVV) and that there were no changes in the HA associated with increased infectivity or transmissibility among people. Additionally, there were no mutations associated with reduced susceptibility to available neuraminidase inhibitor treatments and no mutations identified in other genes indicating additional mammalian adaptation. Genetic data have been posted in GISAID and GenBank. Additional data will be posted as they become available. CDC has successfully isolated virus from specimens from three of the nine cases. Attempts to isolate virus from additional specimens are ongoing. Antigenic characterization and antiviral susceptibility testing are underway. Antigenic characterization will inform whether existing H5 bird flu candidate vaccine viruses (CVVs) would provide good inhibition of these viruses.

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Although much of our attention this summer has been focused on the `bovine' B3.13 genotype which has infected hundreds of dairy herds, some poultry flocks, and has spilled over into at least 24 humans - over the past couple of weeks we've seen the emergence of 2 new genotypes; D1.1 and D1.2.

According to a brief statement (below) from the USDA, the Oregon poultry & swine outbreak of H5N1 was due to genotype D1.2, while the week before we learned that the Washington state outbreak (and spillover into humans) was from genotype D1.1.

A reminder that H5N1 is not a single viral threat, but rather represents a large and growing array of similar viruses all following their own evolutionary pathways.  Additionally, we continue to watch other H5 subtypes (H5N5, H5N6, H5N2, etc.), which also have zoonotic potential.  

You'll find more details on the above mentioned ferret study in Saturday's blog `CDC: Updated Results On Texas H5N1 Virus In Ferrets'.   

The CDC also addresses the other big H5 story from last week, the first detection of H5N1 in a pig in the United States. 

Epidemiology Update

On Wednesday, October 30, 2024, USDA reported an avian influenza A(H5N1) virus infection in a pig on a backyard farm in Oregon. This is the first time an H5 bird flu infection has been reported in a pig in the United States. Sequence data from birds in the avian influenza A(H5) virus outbreak on this backyard farm showed no mutations that caused concerns related to disease severity or adaptability to humans. 

The discovery that an avian influenza A virus has infected a new mammal species is always concerning, especially when the virus is detected in pigs, which are susceptible to influenza viruses circulating in pigs, humans, birds, and other species. These viruses can swap genes through a process called genetic reassortment, which can occur when two (or more) influenza viruses infect a single host. Reassortment can result in the emergence of new influenza A viruses with new or different properties, such as the ability to spread more easily among animals or people. Reassortment events have happened in pigs in the past. A series of reassortment events in pigs is believed to have caused the 2009 influenza A(H1N1) pandemic. Based on available information, the risk to the general public remains low; however, CDC is continuing to gather information.

A multilingual CDC field team continues to assist the California Department of Public Health in its efforts to learn more about how the outbreak in California began and how to lower the risk to farm workers with exposure to infected cows. Two staff members are on the ground in California, and additional staff are ready to deploy if needed. CDC staff are assisting with active surveillance efforts, including field assessments of suspected cases and household contacts; testing and treatment; and dissemination of information to farm workers and the community. A separate CDC field team has returned from deployment to Washington state but continues to work remotely with the local health department on data management and epidemiological summaries. There is no evidence of any person-to-person spread in either of the two states or anywhere in the United States.

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I've only posted some highlights, follow this link to read the full update.

As the CDC states, the detection of H5 in a pig in the United States is concerning, since swine are susceptible to human, swine, and avian flu viruses and have demonstrated the ability to generate reassortments in the past. 

The Oregon spillover is on a small, non-commercial farm - and is likely a dead-end - but other spillovers into larger swine herds are possible. Complicating matters, H5N1 in pigs is often asymptomatic, which makes it more difficult to detect. 

A few past blogs on this topic include:

Emerg. Inf. & Microbes: Pigs are Highly Susceptible To But Do Not Transmit Mink-Derived HPAI

EID Journal: Divergent Pathogenesis and Transmission of Highly Pathogenic Avian Influenza A(H5N1) in Swine

Seroconversion of a Swine Herd in a Free-Range Rural Multi-Species Farm against HPAI H5N1 2.3.4.4b Clade Virus (2023)

Sci. Rpts.: Evidence Of H5N1 Exposure In Domestic Pigs - Nigeria (2018)

For more on all of this, yesterday C Raina MacIntyre and Haley Stone published an informative article in The Conversation on:

Bird flu has been detected in a pig in the US. Why does that matter?

Published: November 4, 2024 2:01pm EST

UKHSA Reports 2 Household Contacts of Imported Mpox Clade Ib Case Test Positive

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Last week the UK became the 5th non-African nation - along with along with India, Thailand, Sweden & Germany - to report an imported clade Ib Mpox case in a traveler recently returned from Africa (see UKHSA Reports 1st Imported Case of Mpox Clade Ib In the UK).

In the UK, the recently emerged clade Ib Mpox virus (unlike the milder clade II) is considered a high consequence infectious disease (HCID), which they define as:

• an acute infectious disease
• typically having a high case-fatality rate
• not always having effective prophylaxis or treatment
• often difficult to recognise and detect rapidly
• able to spread in the community and within healthcare settings
• requiring an enhanced individual, population and system response to ensure it is managed effectively, efficiently and safely

Today the UK's Health Security Agency is reporting that two household contacts of this index case have now tested positive for the virus.  Their very brief statement follows:

Latest update on cases of Clade Ib mpox

The UK Health Security Agency (UKHSA) confirms 2 additional cases of Clade Ib mpox.
From:UK Health Security Agency Last updated 4 November 2024

Two cases of Clade Ib mpox have been detected in household contacts of the first case, the UK Health Security Agency (UKSHA) can confirm. This brings the total number of confirmed cases to 3.

The 2 patients are currently under specialist care at Guy’s and St Thomas’ NHS Foundation Trust in London. The risk to the UK population remains low.

There has been extensive planning underway to ensure healthcare professionals are equipped and prepared to respond to any further confirmed cases.

Professor Susan Hopkins, Chief Medical Adviser at UKHSA, said:

Mpox is very infectious in households with close contact and so it is not unexpected to see further cases within the same household.

The overall risk to the UK population remains low. We are working with partners to make sure all contacts of the cases are identified and contacted to reduce the risk of further spread.

Contacts of all 3 cases are being followed up by UKHSA and partner organisations. All contacts will be offered testing and vaccination as needed and advised on any necessary further care if they have symptoms or test positive.

(Continue . . . )

The Mpox virus continues to evolve, and we now have at least 4 clades of Mpox in circulation (I, Ib, II, IIb), with Clades I and Ib considered the most severe.

As they spread from host-to-host, additional evolutionary changes seem likely (see Evolution of monkeypox virus from 2017 to 2022: In the light of point mutations).

With the end of smallpox vaccinations more than 40 years ago, much of the world's population has little or no immunity to these types of viruses. Smallpox virus may be gone, but the orthopoxvirus family tree contains dozens of branches, including Mpox viruses.

Some of the other poxviruses we've looked at include:

Alaska Health Department Announces A Fatal Alaskapox Infection

A Newly Discovered Poxvirus Detected In Reindeer in Sweden & Norway

EID Journal: Novel Poxvirus in Proliferative Lesions of Wild Rodents in East-Central Texas, USA

A Novel Zoonotic Orthopoxvirus Resurfaces In Alaska