#17,353
Although Taiwan has been plagued by multiple H5 viruses (H5N1, H5N8, H5N2, etc.) in domestic poultry (and wild birds) going back many years, they've been lucky enough not to have to deal with LPAI H9N2, which is ubiquitous across much of Asia and has made recent inroads into Africa and the Middle East (see Viruses: A Global Perspective on H9N2 Avian Influenza Virus).
As an LPAI (low path avian influenza), H9N2 is not considered a `reportable' disease by WOAH (formerly the OIE), even though it is zoonotic, and has at least some pandemic potential.
In their latest update, the WHO mentioned 2 new H9N2 cases in China, and over the years roughly 100 human infections have been reported (see FluTrackers List), although seroprevalence studies (see J. Infect & Public Health: High Seroprevalence Of Avian Influenza H9 Among Poultry Professionals In Pakistan) suggest this is a major under-count.
Most human infections have been mild, although a few severe/fatal cases have been reported. The CDC has 2 different lineages (A(H9N2) G1 and A(H9N2) Y280) on their short list of influenza viruses with zoonotic potential (see CDC IRAT SCORE), and several candidate vaccines have been developed.
But H9N2's biggest threat may come from its unique ability to reassort with other, potentially more dangerous, avian viruses. Its internal genes have often been found inside many HPAI viruses (including H5N1, H5N6, H7N9, and most recently zoonotic H3N8) - (see The Lancet's Poultry carrying H9N2 act as incubators for novel human avian influenza viruses).
The following (translated) statement comes from Taiwan's CDC, which is taking the threat seriously. After which, we'll look at a recent call in The Lancet to contain H9N2 due to its promiscuous nature and ability to reassort with HPAI viruses.
It is currently in the epidemic period of bird flu. Recently, H9N2 virus has been detected in poultry farms. We call on poultry-related staff to wear personal protective equipment correctly when working, and the public to abide by the "5 Dos and 6 Don'ts" principle
Release date: 2023-03-17
The Centers for Disease Control and Prevention stated today (17) that the avian influenza epidemic in domestic poultry farms continues to heat up. A few days ago, a poultry farm detected H9N2 virus, which is the first time that this subtype of virus strain has been detected in a poultry farm in my country. It calls for poultry/animal epidemic prevention work Personnel should wear personal protective equipment and practice respiratory hygiene when working. If you have flu-like symptoms, you should seek medical attention as soon as possible and inform the medical staff of TOCC (travel history, occupation history, contact history, and group history), and the general public should also reduce contact with birds.
The CDC pointed out that for domestic poultry farms where the H9N2 subtype virus was detected, the health unit has assisted the personnel involved in culling and clearing the farms to assist them in putting on and taking off their personal protective equipment, and has compiled a list and carried out health checks as soon as possible. Prevention and control measures such as status tracking.
Currently, there are 20 contact prevention and control personnel and 1 poultry farm personnel. There are 21 people in total, and none of them have flu-like symptoms. In addition, for the contacts of the domestic bird flu epidemic, since January of this year (2023), a total of 695 people (47 cases) of related contacts have been listed in the health management tracking, and no human cases of new type A influenza have been found.
According to the CDC, since 2013, sporadic human cases of H9N2 infection have been continuously reported internationally. So far, at least 97 cases have been reported, of which more than 7 have become young children, 8 cases of severe disease, and 2 cases of death (all with a history of chronic diseases). In Asia, nearly 90% of the cases occurred in China. The latest case was a mild case in Hunan Province, China in November 2022. According to the WHO risk assessment of H9N2 on February 24, 2023, most of the current cases have been exposed to poultry or contaminated environments. As the virus continues to circulate in poultry, sporadic human cases are expected to continue, but current evidence shows that it has not been transmitted from person to person (Human-to-human) ability, the possibility of community transmission is low, but occasional cases of human infection may occur, and close monitoring is required. H9N2 is currently a novel influenza A subtype with "low" disease severity in humans.
The Department of Disease Control and Prevention reminds that due to the continuous occurrence of domestic poultry epidemics, the respiratory secretions and excreta of poultry infected with avian influenza may contain viruses. Entering the human body, the risk of human exposure and infection increases, and livestock-related workers are urged to wear personal protective equipment during work. In order to prevent the new type A influenza, doctors are urged to ask the TOCC (travel history, occupation history, contact history and group history) of patients with influenza-like patients. If they meet the notification requirements of new type A influenza (as attached), they must report as soon as possible .
In addition, the public is requested to abide by the principle of "5 Dos and 6 Don'ts". "5 Dos": Meat and eggs should be cooked, wash hands thoroughly with soap, if symptoms appear, wear a mask to see a doctor immediately and inform the occupation and contact history, and those who have long-term contact with poultry and livestock Inoculate against influenza, eat a balanced diet, and exercise properly; "6 Do's": Do not eat raw poultry eggs or products, do not smuggle or buy meat from unknown sources, do not touch or feed poultry, do not release or discard poultry at will Livestock, do not mix livestock with other livestock, and do not go to places with poor ventilation or crowded places. For relevant information, please visit the Global Information Network of the Centers for Disease Control and Prevention (https://www.cdc.gov.tw/), or call the free epidemic prevention hotline 1922 (or 0800-001922).As a standalone virus, H9N2 ranks pretty far down our pandemic threats list. But as a co-conspirator with another, potentially more dangerous virus, it could provide the genetic bridge needed to efficiently infect and spread among humans.
The following cautionary report was published last fall in The Lancet. I'll have a brief postscript when you return.
The time is now: a call to contain H9N2 avian influenza viruses
Yuhai Bi, Juan Li, Weifeng Shi
Open AccessPublished:September 14, 2022In the past century, we have seen four pandemics caused by human influenza A: H1N1 Spanish influenza (1918–1920), H2N2 Asian influenza (1957–58), H3N2 Hong Kong influenza (1968–69), and H1N1 swine influenza (2009–10). 1 Phylogenetic analyses have shown that reassortment of genetic segments from human, animal, or avian influenza viruses is linked to the origin of the four influenza pandemic strains.
(SNIP)
H9N2 viruses have been reported to be involved in the origin of multiple human-infecting avian influenza viruses, such as H7N9, H10N8, and the recently emerging H3N8 (April, 2022; figure). 3 H9N2 viruses have contributed a complete set, or partial internal genes, to the novel human-infecting avian influenza viruses. Poultry that carry H9N2 avian influenza viruses host an optimal environment for viruses of different subtypes to exchange their gene segments with H9N2 avian influenza viruses.4
Avian influenza viruses with H9N2-derived internal genes would also probably have an increased ability to infect humans. 5 Therefore, poultry that carry H9N2 avian influenza viruses are viewed as genetic incubators for the origin of novel avian influenza viruses that infect humans.4
H9N2 avian influenza viruses show low pathogenicity in birds, and H9N2-infected poultry are often subclinical, presenting with no or very few symptoms; however, avian hosts can shed and transmit the viruses to other clinically vulnerable individuals. Notably, H9N2 avian influenza viruses have been identified in domesticated poultry across China, with stable endemic lineages in commercial chicken flocks.6
Since 2016, H9N2 has also gradually become the dominant avian influenza virus subtype in live poultry markets. 7 More than 100 human cases of H9N2 avian influenza virus have been reported as of July, 2022, including more than 50 cases after the outbreak of COVID-19. 2 A retrospective seroprevalence study revealed that human infection with H9N2 exceeded 10% in occupationally exposed populations (eg, poultry workers, including wholesale sellers and food delivery workers) in seven regions of China sampled between 2014 and 2016.8
The majority of circulating H9N2 avian influenza viruses possess an increased propensity to bind to human-type sialic acid receptors. 7 Therefore, the number of human H9N2 cases has likely been greatly underestimated.In fact, at least 60 countries have reported the identification of H9N2 avian influenza viruses in domesticated and wild birds, including most of the countries in Europe and Asia, and several countries from Africa, and North and South America. Notably, H9N2 avian influenza virus has been found in more than 50 species of wild birds and can infect a diverse range of domesticated and wild mammals, including cats, dogs, pigs, pikas, foxes, and raccoon dogs.
(SNIP)
The pandemic potential of H9N2 avian influenza viruses is shown by the constant emergence of human-infecting avian influenza viruses with H9N2-derived internal genes; the increased human type receptor-binding capacity; the widespread transmission networks in domesticated poultry and wild birds; and the increasingly expanding host spectrum for the viruses. Now is the time to contain H9N2 in China and worldwide. New, effective strategies against H9N2 avian influenza viruses are urgently required, and we recommend development and licensure of vaccines to induce not only humoral immune responses, but also T-cell responses and mucosal immunity to prevent onward viral transmission.
While it would be terrific if there is some unidentified `species barrier' that prevents avian H5 or H7 influenza from sparking a pandemic, it is entirely possible that they just haven't hooked up with the `right' H9N2 virus yet.
Which is definitely something we don't want to learn the hard way.
