J. Virology: Synergistic Effects of PA (S184N) & PB2 (E627K) Mutations on the Increased Pathogenicity of H3N2 Canine Influenza Virus Infections in Mice and Dogs

That is, until spillovers occurred in both species (equine H3N8 in dogs and avian H5N1 in cats) in 2003-2004 (see A Dog & Cat Flu Review).  A few years later (2007), an Avian H3N2 virus spilled over into dogs in Korea, and has since spread globally, arriving in the United States in 2015.

It's been just over a week since the flurry of media reports on the death of a toddler in Andhra Pradesh, India from the H5N1 virus (see Apr 2nd's Media Reports Of Fatal H5N1 Case in Child In Andhra Pradesh, India).

While many of these media reports cite `government sources', over the past week I've not been able to find any confirmation published on an official government website.  

The official X/Twitter  account for Health, Medical & Family Welfare Department, Government of Andhra Pradesh is quite active, with scores of updates for the month of April, but with no mention of H5N1. 

Their webpage (https://hmfw.ap.gov.in/) has links for Notifications and News/Media, but none of them appear to work, and their (COVID centric) Facebook page hasn't been updated since Sept 2022.

Similarly, searches of the Government of India Press Information Bureau (in both English & Hindi) turn up no mention of this case, and only two press releases mentioning H5N1 (here, and here) this month.  Several other Indian govt sites were simply unresponsive despite multiple attempts to access them.

Sadly, this game of hide and seek with official data isn't unusual, and it isn't just from India (see From Here To Impunity).  Our ability to track individual spillovers and outbreaks continues to deteriorate as more and more countries decide there is little to gain by releasing detailed information.

While I've no doubt we'll eventually get an update on this latest human case from India via the WHO, it is disconcerting how much H5N1 activity there appears to be in India, and how few details we are privy to.

Of course we've heard no updates since the initial announcement of the UK's human H5 infection in January, or on the UK's H5N1 infected Sheep reported more than 2 weeks ago.  H5N1 reports have slowed markedly here in the United States since January, and many countries remain completely silent on the threat. 

Two weeks ago we looked a scathing report on the delays (months, sometimes even > 1 year) by countries submitting H5N1 sequence data to GISAID (see Nature: Lengthy Delays in H5N1 Genome Submissions to GISAID).

While I have no way to accurately quantify how much we aren't hearing about H5N1, it is a pretty good bet it is substantial. And this silence extends far beyond just H5N1 (see Flying Blind In The Viral Storm).

A reminder that no news doesn't necessarily mean `good news'.

Although the first PHEIC issued in the summer of 2022 over the international spread of the Clade IIb, Mpox virus was rescinded in 2023 following steep declines in cases (due largely to uptake of the Mpox Vaccine and behavior changes), we continue to see signs of its resurgence. 

Yesterday Vancouver's Coastal Health issued a bulletin warning of increasing numbers of cases in recent months.

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Today you can literally hop on a plane and be in any corner of the world within 24 hours. Millions of airline passengers make international flights each day, and along with their luggage and cell phones, a small percentage will be carrying infectious diseases.

Most viral infections have a 2 to 14 day incubation period, giving an infected traveler a fairly long asymptomatic `window' for travel. 

As we've seen with MERS-CoV, Mpox, H5N1, and Ebola - most of these viral introductions have failed to take root - but the rapid global spread of the SARS-CoV-2 virus in early 2020 illustrates how quickly the status quo can change.

In late April sixteen years ago - at at time when H5N1 was our biggest pandemic concern - the world was blindsided by a swine-origin H1N1 pandemic that began in Mexico, and quickly swept the globe. 

While milder than the three influenza pandemics that preceded it (1968, 1957, 1918), the CDC had this to say about its impact on a younger cohort in 2012's First Global Estimates of 2009 H1N1 Pandemic Mortality Released by CDC-Led Collaboration.

2009 H1N1 Pandemic Hits the Young Especially Hard

This study estimated that 80% of 2009 H1N1 deaths were in people younger than 65 years of age which differs from typical seasonal influenza epidemics during which 80-90% of deaths are estimated to occur in people 65 years of age and older.

Although the pandemic lasted barely a  year, it reinforced our concerns over the ability of swine-origin H1, H2, or H3 viruses to spillover into humans (see graphic above).  Since then we've seen more than 500 such spillovers in the United States alone. 

We've seen similar reports from Europe, South America and Asia, although surveillance of pigs and humans for swine flu (even in the United States and Europe) is extremely limited. 

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The ECDC maintains a Swine influenza Factsheet, which describes the introduction and spread of influenza viruses in European pigs.

Current influenza viruses in European pigs

Avian-like swine A(H1N1) influenza viruses (SIVs) of the subtypes A(H1N1), A(H3N2) and A(H1N2) are enzootic and widespread in swine producing regions of Western Europe. The first known introduction of human influenza virus into swine populations occurred after the Spanish flu in 1918 and this lineage was called ‘classical swine’ H1N1 (or lineage 1A). This lineage is still present in pigs in the Americas and Asia, but has not been detected in European pigs in the last two decades.

The first significant outbreak of an avian A(H1N1) influenza virus lineage occurred in 1979 and led to the establishment of an ‘avian-like’ A(H1N1) virus lineage in European pigs. This virus, referred to as Eurasian avian-like 1C lineage, rapidly established itself in Europe and has continued to circulate in swine until the present day.

Contemporary swine A(H3N2) influenza viruses in European pigs descend from early human influenza A(H3N2) pandemic strains, and have diverged substantially genetically and antigenically from contemporary human viruses. The A(H1N2) influenza viruses were established in Europe with the reassortment of swine A(H3N2) viruses and a human-seasonal A(H1N1) virus (H1huN2) and to date are still circulating among European pig populations.