All human infections caused by a new subtype of influenza virus are notifiable under the International Health Regulations (IHR, 2005). State Parties to the IHR (2005) are required to immediately notify WHO of any laboratory-confirmed case of a recent human infection caused by an influenza A virus with the potential to cause a pandemic. Evidence of illness is not required for this report.
• Sporadic human infections with avian influenza virus A(H3N8), A(H5N1), A(H5N6), A(H9N2) and A(H10N3) were reported globally in 2022.• Outbreaks and detections of highly pathogenic avian influenza viruses, mainly A(H5N1), affected poultry, wild and captive birds worldwide in 2022.• In 2022, human infections with influenza virus A(H1N1)v and A(H1N2)v of swine origin were detected in two EU/EEA countries: Germany and the Netherlands, respectively.• Outside of the EU/EEA, influenza virus A(H1N1)v, A(H1N2)v, and A(H3N2)v of swine origin caused sporadic human infections in Brazil, China, Taiwan, and the United States (US).
IntroductionAnimal influenza viruses that usually circulate in animal species can, in rare occasions, transmit to humans and cause zoonotic influenza virus infections. Most zoonotic influenza virus infections in humans are caused by avian influenza or swine influenza viruses that circulate in wild birds and spill over to farmed poultry as well as pig populations, respectively. Infections are typically related to direct contact with sick or dead animals which are infected, or contaminated environments. Infections can result in asymptomatic, mild or severe disease, causing symptoms which range from fever, conjunctivitis and cough to severe pneumonia, but can also cause atypical symptoms like gastroenteritis.MethodsThis report is based on data for 2022, retrieved in March 2023 from different sources, such as the World Health Organization (WHO), the World Organisation for Animal Health (WOAH), the European Food Safety Authority (EFSA), and ECDC’s epidemic intelligence activities.
This report includes events and data from 2022. It does not cover the entire winter-season pattern. The date of identification or onset of symptoms was used, and if not available, the date of reporting.
Since September 2017, ECDC, together with EFSA and the European Union Reference Laboratory for Avian Influenza (EURL), have been publishing quarterly updates on the avian influenza situation in the EU/EEA (see link) .All the avian influenza detections in humans and birds for 2022 listed in the subsequent sections have been published in the avian influenza situation reports [2-6].
Avian influenza in humansAvian influenza virus A(H3N8)In 2022, China reported two children infected with avian influenza virus A(H3N8) reassortant virus – both children were exposed to live poultry before the onset of symptoms [3,7]. These are the first two cases of human avian influenza A(H3N8) globally.Avian influenza virus A(H5N1)In 2022, six human cases with avian influenza virus A(H5N1) were reported globally. In Europe, Spain detected viral fragments of A(H5N1) in specimens taken from two asymptomatic poultry workers involved in culling and cleaning activities during an avian influenza outbreak at the same farm. However, productive infection was ruled out, and a contamination was considered [5,6,8]. Similarly, in the US, a low level of viral fragments was detected in a worker identified with mild symptoms (fatigue), who was involved in culling activities [3,6,7]. One lethal case of an individual exposed to backyard poultry was reported by China [5,6,8]. One human infection with avian influenza virus A(H5N1) was reported in Vietnam, in a five-year-old girl exposed to sick poultry [5,8,9]. For the first time, an avian influenza virus infection was reported in South America: a nine-year-old girl developed severe symptoms following exposure to sick and dead backyard poultry in Ecuador [6,10].Avian influenza virus A(H5N6)In 2022, 18 human cases of avian influenza virus A(H5N6) were reported from China, including three deaths. All the cases were exposed to infected poultry or virus-contaminated environments, such as live poultry markets. However, the source of exposure is unknown for one case [3-5,7,9,11-17].Avian influenza virus A(H9N2)In 2022, 16 human cases of avian influenza virus A(H9N2) were reported globally. Out of these, 15 were reported from China (one adult, and the remaining children). Among the cases with known exposure, all the infected individuals were exposed to poultry [3-5,8,9,12-15,17,18]. In addition, Cambodia reported one case of avian influenza virus A(H9N2) in a one-year-old female with exposure to backyard poultry .Avian influenza virus A(H10N3)
One human case of avian influenza virus A (H10N3) was reported from China in 2022, following exposure to backyard poultry [4,16]. This was the second human case of avian influenza virus A (H10N3), after the first reported from China in 2021.Swine influenza in humansSwine influenza virus A(H1N1)v
In 2022, four human cases of swine influenza virus A(H1N1)v were reported globally – with individuals mostly experiencing mild respiratory symptoms, such as fever and cough. In Europe, Germany reported one case of infection with swine influenza virus A(H1N1)v in a 34-year-old female. Although the patient was not directly exposed to swine, she lived in a region with many swine farms and had contacts with swine farmers . Two cases were reported in China, one in a six-year-old girl and another in a three-year old girl [16,18]. In addition, one case of human infection with swine influenza virus A(H1N1)v was reported in a 60-year-old female in Brazil, living with domestically raised pigs .
Swine influenza virus A(H1N2)v
In 2022, seven cases of human infection with swine influenza virus A(H1N2)v were reported globally. Infections caused mild respiratory disease in most cases. However, one individual was hospitalised. In Europe, the Netherlands reported one case of humaninfection with swine influenza virus A(H1N2)v in a young adult female working at a pig farm . The US reported five cases of swine influenza virus A(H1N2)v; of these, the cases with known exposure attended agricultural events [15,16,19]. In addition, Taiwan reported its first case of human infection with swine influenza virus A(H1N2)v – the case was a seven-year-old girl whose family owned a pig barn .
Swine influenza virus A(H3N2)v
In 2022, five cases of human infection with swine influenza virus A(H3N2)v were reported from the US. All the cases experienced mild respiratory illness and had contact with swine, most of which was at agricultural events [8,15,19].to the vest
Between the `fog' and fatigue of COVID - and increasing economic and political tensions around the globe - the quantity and quality of infectious disease surveillance and reporting around the world has suffered over the past few years.
Despite the `legally binding' reporting requirements of the IHR 2005, many countries have figured out that there is little downside to withholding outbreak or spillover information close.
Even in countries that are actively looking, public health officials openly admit that their ability to detect sporadic human cases of novel flu is limited (see UK Novel Flu Surveillance: Quantifying TTD).
As a result, we have no idea how pervasive these types of events really are.