欧洲疾控中心-人畜共患流感-2023年年度流行病学报告（英）-2025_6页_488kb

Zoonotic Influenza Annual Epidemiological Report for 2023

Core Content Summary

This report presents the global epidemiological situation of zoonotic influenza viruses in humans during 2023. Zoonotic influenza viruses, which originate from animals, can occasionally transmit to humans, but sustained human-to-human transmission has not been observed. The report highlights the prevalence of avian and swine influenza viruses in animal populations and their sporadic impact on human health.

Key Facts

• Avian Influenza (AI) Viruses: Sporadic human infections with A(H3N8), A(H5N1), A(H5N6), A(H9N2), and A(H10N5) were reported globally by four countries in 2023.
• Swine Influenza (SI) Viruses: Human infections with A(H1N1)v, A(H1N2)v, and A(H3Nx)v were reported by eight countries.
• EU/EEA Situation: No human cases of avian influenza were reported in the EU/EEA in 2023, while sporadic cases of swine influenza were noted in the Netherlands and Spain.
• Transmission Patterns: Most human infections result from direct contact with infected animals or contaminated environments. Symptoms range from mild to severe, with some cases leading to hospitalisation or death.
• Trend: A decrease in reported avian influenza cases was observed in 2023 compared to 2021 and 2022, especially for A(H5N6) and A(H9N2).

Epidemiology Overview

Avian Influenza in Humans

• Global Cases: 29 cases or detections of avian influenza viruses were reported in 2023, with the majority (18) coming from China.
• Fatal Outcomes: 8 out of 29 cases resulted in fatalities (28%), and 16 were hospitalised (59%).
• Exposure History: All but one of the reported cases had a history of exposure to poultry or contaminated environments.

Subtypes Reported

• A(H3N8): 1 fatal case in China, the first known death from this subtype.
• A(H5N1): 12 cases globally, including 4 in the UK (3 asymptomatic, 1 mild), 6 in Cambodia (4 fatal), and 1 in Chile.
• A(H5N6): 6 cases in China, all hospitalised, with 2 fatalities.
• A(H9N2): 9 cases in China, all recovered, with 6 in children.
• A(H10N5): 1 fatal case in China, co-infected with seasonal influenza A(H3N2), with exposure to live ducks.

Swine Influenza in Humans

• Global Cases: 11 cases of swine-origin influenza viruses were reported in 2023, with subtypes A(H1N1)v, A(H1N2)v, and A(H3Nx)v.
• Country Distribution: Cases reported by the US (3), Brazil (2), China, Taiwan, Netherlands, Spain, Switzerland, and the UK (1 each).
• Symptoms: Most infections were mild, with only two hospitalisations, including one fatal case in a person with underlying conditions.

Subtypes Reported

• A(H1N1)v: 6 cases globally, with 5 in adults and 1 in a child under 5.
• A(H1N2)v: 4 cases reported by the US, Taiwan, and UK, with 3 in individuals under 18 and 1 in an individual over 75.
• A(H3Nx)v: 1 case in the US, an 11-year-old girl with mild respiratory illness.

Main Points and Insights

• Sporadic Transmission: Human infections with zoonotic influenza viruses remain infrequent despite widespread animal transmission.
• Risk Factors: Direct contact with infected animals or contaminated environments is a common risk factor.
• Geographic Focus: China and Cambodia were the main countries reporting human cases of avian influenza, while the US, Brazil, and several EU/EEA countries reported swine-origin infections.
• Severity: While most infections are mild, some cases resulted in hospitalisation or fatality, especially in individuals with pre-existing conditions.
• Need for Surveillance: The report underscores the importance of continued surveillance and the One Health approach to monitor and mitigate risks associated with zoonotic influenza viruses.

Conclusion

Zoonotic influenza viruses continue to circulate widely in animal populations, particularly in birds and pigs. Although human infections are rare, they can occur and lead to severe outcomes. The report highlights the need for vigilance, timely reporting, and integrated approaches to prevent and control the spread of these viruses to humans.