ECDC Epidemiological Updates: Avian H10N3 In China & Novel H1N2v in US

 #16,000

Between social distancing, facemasks, hand hygiene and a potential suppressive impact from the coronavirus itself (aka `viral interference'), community transmission of seasonal influenza (H1N1, H3N2, Influenza B) has practically disappeared (see FluView Comparison chart above) - both in the United States and globally - over the past 14 months.

Seasonal flu has been so scarce that influenza reference laboratories around the globe have had few samples to sequence (see ECDC Influenza Virus Characterisation - Summary Europe, March 2021), raising concerns over what might be brewing out of our sight.

But one aspect of influenza transmission that COVID has not changed all that much is the human-animal interface. People still work, and often live around, animals (particularly swine and poultry) that can harbor, and occasionally transmit, novel flu viruses to humans.

Over the past 10 days we've seen three such reports - 1 in China, and 2 in the US - although it is pretty safe to assume it happens considerably more often than is picked up by surveillance.   

• Last Friday, in CDC FluView Week 21: Novel H1N1(v) Influenza Infection Reported In Iowa, we looked at the second swine variant infection reported in the US in a week (see CDC FluView Week 20: Novel H1N2(v) Influenza Infection Reported In Ohio).

• Five days ago, we looked at the first known instance of an avian H10N3 virus jumping to humans, in CHINA NHC Reports 1st Human H10N3 Avian Flu Infection - Jiangsu Province.

• Earlier this year, we saw H5N8 infect humans for the first time (see Russian Media Reports 7 Human Infections With Avian H5N8).

• China has reported at least a dozen avian H9N2 infections since the 1st of the year. 

• And in 2021 we've seen scattered reports of swine variant infections from Canada, Brazil, and two more from the United States 

But the truth is, most countries aren't looking for these types of infections.  And history has shown that even among countries that are looking, some are reluctant or very slow to report them publicly.  We've seen this not only with avian flu, but with MERS-CoV, COVID, and other infectious diseases. 

Despite the limits of surveillance and reporting, we've seen a decided uptick in zoonotic influenza cases the past 10 months, arising from both birds and swine.  We've seen two new zoonotic viruses with at least some pandemic potential (EA H1N1 `G4' from China, and HPAI H5N8) added to the CDC's IRAT List, on top of 3 more (2 swine-variant, 1 avian H9N2) added in 2020.

The truth is, as much as we don't want to have to deal with it in the midst of the coronavirus pandemic, nature's laboratory is open 24/7 and doing multiple, unsupervised, gain of function experiments.

Most of these experiments will fail, of course.  A `pandemic capable' virus only rarely emerges. But it only takes one success to spark the next global health crisis. 

On Friday the ECDC published epidemiological assessments on the two latest zoonotic events (H10N3 in China, and H1N2v in the US) in their weekly Communicable Disease Threats Report (CDTR). 

I'll have a postscript after the break. 

New! Influenza A(H10N3) - China - 2021

Opening date: 1 June 2021 Latest update: 4 June 2021

Epidemiological summary On 1 June 2021, Chinese health authorities reported a human case with A(H10N3) avian influenza infection in Zhenjiang, Jiangsu, China. This is the first case of human infection with avian influenza A(H10N3) in the world. The patient is a 41-year-old man who developed symptoms on 23 April 2021. He was hospitalised on 28 April and is now in a stable condition. No further cases were identified among the contacts of the patient. 

Whole genome sequencing showed the infection was caused by A(H10N3) influenza virus of avian origin. According to the Chinese authorities, the virus did not have the ability to effectively infect humans. Influenza A(H10N3) virus is considered a low pathogenic avian influenza.

 

Sources: National Health Commission of the People's Republic of China | The Government of the Hong Kong Special Administrative Region 

ECDC assessment 

This is the first human case of influenza A(H10N3) virus infection. No human-to-human transmission has been reported and further investigations on exposure as well as on the virus characteristics are needed to understand the circumstances of the transmission to human. Sporadic zoonotic transmission cannot be excluded, the use of personal protective measures for people exposed to poultry and birds with avian influenza viruses will minimise the remaining risk. The risk of zoonotic influenza transmission to the general public in EU/EEA countries is considered to be very low. 

Actions 

ECDC monitors avian influenza strains through its epidemic intelligence activities in order to identify significant changes in the epidemiology of the virus. ECDC, together with EFSA and the EU reference laboratory for avian influenza, produces a quarterly updated report of the avian influenza situation. The most recent report was published on 31 May 2021. Cases should be reported immediately to EWRS and IHR.

New! Human infection with influenza A(H1N2) variant virus ±US ± 

Opening date: 1 June 2021 Latest update: 4 June 2021

Epidemiological summary 

At the end of May 2021, the US CDC reported about a confirmed human case with A(H1N2)virus variant (A(H1N2)v) infection in Ohio, the US. The patient is <18 years of age, he was not hospitalised and has recovered from the illness. No human-to-human transmission of influenza A(H1N2)v has been identified associated with this case. Investigation into the source of the infection revealed that the case lives on a farm where pigs are present. This is the first case detected this year in the US. 

Source: the US CDC 

ECDC assessment 

Sporadic cases of A(H1N2)v infection occur in humans who have direct or indirect contact with pigs and contaminated environments. Since 2005, 29 cases of A(H1N2)v infection have been reported worldwide, of which 27 in the US. Further epidemiological investigations, including the characterisation of the virus, are needed to assess the source of infection and risk of transmission to humans as well as between humans. Close cross-sectoral cooperation and communication between animal and public health authorities are recommended to better understand the circulating viruses in pigs in order to implement safety measures and prevent zoonotic transmission events. Detailed virus characterisation analyses for unsubtypable influenza viruses should be performed and specimens shared with national influenza centres or reference laboratories. 

Actions 

ECDC is monitoring zoonotic influenza events through epidemic intelligence activities in order to identify significant changes in the epidemiology of the virus. Cases should be reported immediately to EWRS and IHR.

Although we watch these novel flu viruses closely looking for signs that one of them may becoming better adapted to humans, thereby posing a pandemic threat, the eventual return of seasonal flu is also a major concern. 

After a year without appreciable seasonal flu - and community immunity to seasonal influenza strains presumably waning with each passing month - we are entering uncharted territory.

 

When flu eventually does return, our collective immune `shields' may be down, and even seasonal H1N1, H3N2, or influenza B could prove a major challenge, much as we saw in 2018's high-severe flu season.. 

There are also concerns that - as long as seasonal flu remains at bay - that viral vacuum may provide a more permissive environment for novel flu strains to emerge and circulate (see PLoS Comp. Bio.: Spring & Early Summer Most Likely Time For A Pandemic).

All reasons why we must remain vigilant for the next pandemic threat, even as we battle the current one.