#17,947
Every couple of months the World Health Organization publishes their latest Influenza at the Human-Animal Interface report, which summarizes recently reported zoonotic flu infections from around the world.
Most of these cases have been previously reported, although additional details may be provided.
Yesterday's update covers the period from December 22nd 2023 to February 26th, 2024, and it includes 11 novel flu infections, 10 of which were officially reported to WHO and a 11th, announced yesterday by Hong's CHP (see graphic above), that was conveyed to WHO unofficially by researchers.
With each subtype reported, the WHO provides an updated risk assessment, and the report contains the standard pleas for countries to abide by the IHR rules and report all cases immediately.
Due to its length, I've only posted some excerpts. Follow the link to read it in its entirety. I'll have a brief postscript after the break.
New infections : From 22 December 2023 to 26 February 2024, five human cases of infection with influenza A(H5N1) viruses, one human case of infection with an A(H5N6) influenza virus, one human infection with an A(H9N2) virus, one human case of infection with an A(H10N5) virus, and two human cases of infection with influenza A(H1N1) variant viruses were reported officially. Additionally, one human case of infection with an influenza A(H9N2) variant virus was detected.
• Risk assessment: The overall public health risk from currently known influenza viruses at the human-animal interface has not changed, and sustained human-to-human transmission of the viruses from these cases is currently considered unlikely. Although human infections with viruses of animal origin are unusual, they are not unexpected at the human-animal interface wherever these viruses circulate in animals.
• Risk management: New candidate vaccine viruses (CVVs) for zoonotic influenza viruses for pandemic preparedness purposes were selected through a recent WHO consultation.3
• IHR compliance: All human infections caused by a new influenza subtype are required to be reported under the International Health Regulations (IHR, 2005).2F 4 This includes any influenza A virus that has demonstrated the capacity to infect a human and its haemagglutinin gene (or protein) is not a mutated form of those, i.e. A(H1) or A(H3), circulating widely in the human population. Information from these notifications is critical to inform risk assessments for influenza at the human-animal interface.
After an absence of 9 years, in early 2023 Cambodia reported the first of 6 H5N1 cases (clade 2.3.3.1c) in 2023, which was followed in January and February of 2024 with 5 more cases (see chart below).
Avian influenza A(H5) viruses A(H5N1), Cambodia Since the last risk assessment of 21 December 2023, five human cases of infection with A(H5N1) influenza viruses were notified to WHO from Cambodia (see Table 1).
The A(H5N1) viruses from the first four cases belong to the H5 haemagglutinin (HA) clade 2.3.2.1c. Viruses belonging to this clade have been detected in poultry since 2014 in Cambodia in longitudinal surveillance done in the animal health sector. Clade information on the virus from the last case reported in Kampot province has not yet been determined.
Based on the phylogenetic patterns, the third and fourth cases were likely exposed to the same source, although the possibility of human-tohuman transmission cannot be excluded. No further cases or evidence of sustained human-to human transmission were reported.
Additionally, China reported 1 case of H5N6 during this reporting period. The onset of this patient's illness was in late November of 2023, but the case was not reported by China until early 2024.
Since the risk assessment of 21 December 2023, one human case of infection with an A(H5N6) influenza virus was notified to WHO from China on 3 January 2024. A 59-year-old woman, with underlying comorbidities, from Sichuan province developed illness on 25 November 2023 and was hospitalized with severe pneumonia on 29 November. As of 9 January 2024, she was improving. She had exposure to a live poultry market. Environment samples from the market tested positive for influenza A(H5). No further cases were detected among her contacts.
According to reports received by the World Organisation for Animal Health (WOAH), various influenza A(H5) subtypes continue to be detected in wild and domestic birds in Africa, Asia, Europe and the Americas. Infections in non-human mammals are also reported.
China also reported 2 H9N2 cases (albeit 1 through unofficial channels).
A(H9N2), China Since the last risk assessment of 21 December 2023, two human cases of infection with A(H9N2) influenza viruses were notified to WHO from China. On 22 February 2024, the International Health Regulations (IHR) Contact Point of Hong Kong SAR, China notified WHO of one human infection with avian influenza A(H9N2). A two-year-old girl had an onset of influenza-like illness (ILI) symptoms on 15 February 2024. She went to hospital on 16 February where a sample was collected, and she was not hospitalized at that time. She was admitted to the isolation ward of a public hospital and was in in stable condition at the time of reporting. According to the initial investigation, the patient visited Guangdong province during the incubation period. The patient has no known poultry exposure or consumption of undercooked poultry. One of her home contacts developed a sore throat on 17 February, but the symptoms subsided, and the contact was not sampled. Other home contacts remain asymptomatic. The epidemiological investigations are ongoing.
Additionally, one human case of infection with an influenza A(H9N2) virus was detected in China according to information received during the WHO Consultation and Information Meeting on the Composition of Influenza Virus Vaccines for Use in the 2024-2025 Northern Hemisphere Influenza Season held in February 2024. 3 A six-year-old boy from Anhui province developed illness on 3 January 2024. Avian influenza A(H9N2) viruses are enzootic in poultry in Asia and increasingly reported in poultry in Africa.
Avian influenza A(H10N5) virusesSince the last risk assessment on 21 December 2023, one human case of infection with an influenza A(H10N5) virus was reported from China. A 63-year-old female, with chronic comorbidities, from Anhui province developed fever, a cough and sore throat on 30 November 2023. She was admitted to hospital on 2 December, was transferred to a medical institution in Zhejiang province on 7 December and passed away on 16 December.Zhejiang Province health officials isolated seasonal influenza A(H3N2) subtype and avian influenza A(H10N5) subtype viruses from the patient’s samples on 22 January after nucleic acid testing, viral culture and gene sequencing conducted by local health care facilities. The patient had exposure to live poultry through the purchase of a duck on 26 November. From the duck meat stored in the fridge, seven samples tested positive for influenza A(H10N5), and two samples were positive for N5 (no result for haemagglutinin).
The agricultural authority has conducted culling and hazard management of the ducks which tested positive for A(H10N5) in a traceback investigation and has carried out disinfection of affected areas. The patient had no contact with pigs or other mammals. Environmental samples collected from her home tested negative for influenza viruses. Monitoring of close contacts did not identify any further cases. This is the first case of human A(H10N5) infection detected in China and globally
And lastly, reports on two swine variant H1N1v infections. One in Brazil, and the other in Spain.
Since the risk assessment of 21 December 2023, one human infection with an influenza A(H1N1) variant virus [A(H1N1)v] was reported from Brazil and one was reported from Spain.
A(H1N1)v, Brazil
On 16 January 2024, Brazil notified WHO of a laboratory-confirmed human infection with swine-origin influenza A(H1N1)v virus, in the State of Paraná. The patient, an adult male who had underlying medical conditions, developed ILI symptoms on 12 December 2023 and was hospitalized on 16 December. He had no history of exposure to pigs. He did not receive antiviral treatment but fully recovered on 18 December, when he was discharged from the hospital. From the epidemiological investigation, no close contacts were identified
A(H1N1)v, Spain
On 29 January 2024, the Spanish health authorities notified WHO of a laboratory confirmed human case of infection with swine-origin influenza A(H1N1)v virus, in the province of Lleida (Cataluña autonomous community). An adult male adult male, who worked on a pig farm in the province of Lleida, developed ILI symptoms on 25 November 2023. He sought medical care at an outpatient clinic on 29 November and was seen again twice in December 2023, where he was diagnosed with bronchitis. He did not receive antiviral treatment and has completely recovered.
As always, surveillance and timely reporting of cases remains a challenge. Whether deliberately, or due to a lack of resources, many countries still fail to meet their obligations to report novel flu infections in a timely manner.
Last April, in Lancet Preprint: National Surveillance for Novel Diseases - A Systematic Analysis of 195 Countries, we looked at an independent analysis which suggests that many nations have substantially overstated their compliance with the 2005 IHR regulations, and that surveillance and reporting are far less robust than advertised.
And in far too many countries, `Don't test, don't tell' has - for political, economic, and societal reasons - become unofficial policy. Even when disease reports are provided, they sometimes come weeks or months after the fact, and are often lacking in detail.
But even in countries that are actively looking, it is likely that only a small fraction of cases are ever identified.
A year ago, in UK Novel Flu Surveillance: Quantifying TTD, we looked at concerns that the TTD (Time to Detect) community spread of a novel virus - even in the UK - could be weeks, and then only after hundreds of cases.
A reminder than anything we say about the current threat posed by H5N1, H3N8, MERS-CoV, or any other pandemic threat must carry an implied asterisk.
A disclaimer that says, ` * based on available, and likely incomplete, information. . . '.
