Commonground
Senior Moderator
This week’s topics
1. Influenza A(H5N1) – Multi-country (World) – Monitoring human cases
2. Avian influenza A(H9N2) – Multi-country (World) – Monitoring human cases
3. Overview of respiratory virus epidemiology in the EU/EEA
4. Outbreak of Salmonella Bovismorficians - Multi-country - 2026
Executive summary
Influenza A(H5N1) – Multi-country (World) – Monitoring human cases
• On 21 April 2026, Cambodia's Ministry of Health reported a new human case of avian influenza
A(H5N1) virus infection in an adult woman from Romduol district, Svay Rieng province.
• The patient is being isolated and receiving medical treatment in hospital.
• The patient had exposure to sick and dead poultry before disease onset.
• Since 2003, a total of 998 confirmed human cases of A(H5N1) have been reported worldwide,
including 477 deaths (case fatality rate (CFR): 48%).
• ECDC’s risk assessment for A(H5N1) remains unchanged. Overall, the risk related to zoonotic
influenza for the general population in the EU/EEA is considered low.
Avian influenza A(H9N2) – Multi-country (World) – Monitoring human cases
• As of 22 April 2026, five new human cases of avian influenza A(H9N2) virus infection were
reported in China, with symptom onset in January, February and March 2026.
• Four cases were in children five years old or younger from different provinces and one adult in
his 60s.
• Exposure information is not provided in the public domain.
• Overall, 201 human cases of avian influenza A(H9N2), including two deaths, have been reported
globally since 1998 by 11 countries.
• The risk to human health in the EU/EEA is currently considered very low.
European Centre for Disease Prevention and Control, Solna, Sweden
www.ecdc.europa.eu
Overview of respiratory virus epidemiology in the EU/EEA
Summary
In week 16, 2026, the number of people reporting symptoms of respiratory illness is at baseline to
low levels and continues to decrease across the EU/EEA.
Respiratory syncytial virus (RSV) appears to be the main contributor to respiratory virus activity.
Circulation is moderate but decreasing, and the seasonal peak has passed. Activity remains highest
among children aged 0 to 4 years and adults aged 60 years and above, although trends suggest a
general decline across all age groups.
Influenza virus activity has returned to inter-seasonal levels in almost all countries, with low levels
of detections and hospitalisations reported in all age groups.
SARS-CoV-2 activity remains at very low levels in all countries and all age groups, with no evidence
of increased transmission at this time.
All data are provisional and may be affected by reporting delays, incomplete country data or low
testing volumes. A few countries with high testing rates can disproportionately influence pooled
data. Further information is available under ‘Country notes’ and ‘Additional resources’
.
Outbreak of Salmonella Bovismorficians – Multi-country – 2026
• A multicountry outbreak of Salmonella Bovismorbificanshas been detected with about 50
confirmed cases in January to April 2026.
• All cases are adults, predominantly female. At least five cases have been hospitalised.
• Sprouted seeds/microgreens are identified as common source of infection in Ireland, Finland
and the UK.
• Five additional countries have identified closely related isolates in cases from the same period,
or observed an increase in this serotype, but without further information on food consumption
or travel history.
1. Influenza A(H5N1) – Multi-country
(World) – Monitoring human cases
Overview:
On 21 April 2026, Cambodia's Ministry of Health reported a new human case of avian influenza
A(H5N1) virus infection in a woman in her 60's from Romduol district, Svay Rieng province.
The patient is currently isolated in hospital and is receiving treatment. Epidemiological investigations
revealed that the patient had contact with poultry and that there had been sick and dead poultry
both in the household and in the village between 2 and 13 April 2026. On 21 April 2026, the National
Institute of Public Health confirmed infection with avian influenza A(H5N1). No additional information
is available at this time.
National and local authorities are actively investigating the event and implementing response
measures. As part of the response, close contacts of the case have received antiviral prophylaxis
(oseltamivir), and health education campaigns are ongoing in the affected villages.
This is the fourth human case reported in Cambodia this year. The most recent, previous case (in a
child) was reported on 31 March 2026. Information about the virus clade has not been reported for
the recent cases. Clade 2.3.2.1e has been circulating among birds in Cambodia and has been
detected in infected humans in the recent past. Overall, since 2003, Cambodia has reported 93
cases, including 52 deaths (CFR: 56%).
Summary:
Since 2003, there have been 998 human cases of avian influenza A(H5N1) infection worldwide*,
including 477 deaths (CFR: 48%). These cases have been reported in 25 countries (Australia
(exposure occurred in India), Azerbaijan, Bangladesh, Cambodia, Canada, Chile, China, Djibouti,
Ecuador, Egypt, India, Indonesia, Iraq, Laos, Mexico, Myanmar, Nepal, Nigeria, Pakistan, Spain,
Thailand, Türkiye, Viet Nam, the United Kingdom (UK), and the United States (US)). To date, no
sustained human-to-human transmission has been detected.
* This includes detections due to suspected environmental contamination, with no evidence of
infection, that were reported in 2022 and 2023 by Spain (two detections), the US (one), and the UK
(four, one of which was inconclusive). Human cases of A(H5) epidemiologically linked to A(H5N1)
outbreaks in poultry and dairy cattle in the US are included in the reported number of cases of
A(H5N1).
Acknowledgements: we gratefully acknowledge all data contributors, i.e. the authors and their
originating laboratories responsible for obtaining the specimens, and the submitting laboratories for
generating the genetic sequences and metadata and sharing via the GISAID Initiative.
ECDC assessment:
Sporadic human cases of different avian influenza A(H5) subtypes have previously been reported
around the world. Current virological evidence suggests that circulating A(H5N1) viruses retain
genetic characteristics consistent with avian-adapted influenza viruses. Despite the widespread
transmission of avian influenza viruses in animals, transmission to humans remains infrequent and
no sustained transmission between humans has been observed.
Based on the currently available information, the overall risk related to zoonotic influenza for the
general population in the EU/EEA is considered low.
Direct contact with birds and other infected animals, their secretions or a contaminated environment
is the most likely source of infection. Application of personal protective measures in people exposed
to infected animals or their environment can reduce the associated risk. The recent severe cases in
Asia and the Americas in children and people exposed to infected, sick or dead backyard poultry
underline the risk of unprotected contact with infected birds in backyard farm settings. This supports
the importance of using appropriate personal protective equipment.
Actions:
ECDC monitors avian influenza strains through its influenza surveillance programme and epidemic
intelligence activities in collaboration with the European Food Safety Authority (EFSA) and the EU
Reference Laboratory for Avian Influenza in order to identify significant changes in the virological
characteristics and epidemiology of the virus. Together with EFSA and the EU Reference Laboratory
for Avian Influenza, ECDC produces a quarterly updated avian influenza overview. The most recent
report was published in March 2026.
Last time this event was included in the Weekly CDTR: 1 April 2026
https://www.ecdc.europa.eu/sites/default/files/documents/2026-WCP-0021 Final.pdf
1. Influenza A(H5N1) – Multi-country (World) – Monitoring human cases
2. Avian influenza A(H9N2) – Multi-country (World) – Monitoring human cases
3. Overview of respiratory virus epidemiology in the EU/EEA
4. Outbreak of Salmonella Bovismorficians - Multi-country - 2026
Executive summary
Influenza A(H5N1) – Multi-country (World) – Monitoring human cases
• On 21 April 2026, Cambodia's Ministry of Health reported a new human case of avian influenza
A(H5N1) virus infection in an adult woman from Romduol district, Svay Rieng province.
• The patient is being isolated and receiving medical treatment in hospital.
• The patient had exposure to sick and dead poultry before disease onset.
• Since 2003, a total of 998 confirmed human cases of A(H5N1) have been reported worldwide,
including 477 deaths (case fatality rate (CFR): 48%).
• ECDC’s risk assessment for A(H5N1) remains unchanged. Overall, the risk related to zoonotic
influenza for the general population in the EU/EEA is considered low.
Avian influenza A(H9N2) – Multi-country (World) – Monitoring human cases
• As of 22 April 2026, five new human cases of avian influenza A(H9N2) virus infection were
reported in China, with symptom onset in January, February and March 2026.
• Four cases were in children five years old or younger from different provinces and one adult in
his 60s.
• Exposure information is not provided in the public domain.
• Overall, 201 human cases of avian influenza A(H9N2), including two deaths, have been reported
globally since 1998 by 11 countries.
• The risk to human health in the EU/EEA is currently considered very low.
European Centre for Disease Prevention and Control, Solna, Sweden
www.ecdc.europa.eu
Overview of respiratory virus epidemiology in the EU/EEA
Summary
In week 16, 2026, the number of people reporting symptoms of respiratory illness is at baseline to
low levels and continues to decrease across the EU/EEA.
Respiratory syncytial virus (RSV) appears to be the main contributor to respiratory virus activity.
Circulation is moderate but decreasing, and the seasonal peak has passed. Activity remains highest
among children aged 0 to 4 years and adults aged 60 years and above, although trends suggest a
general decline across all age groups.
Influenza virus activity has returned to inter-seasonal levels in almost all countries, with low levels
of detections and hospitalisations reported in all age groups.
SARS-CoV-2 activity remains at very low levels in all countries and all age groups, with no evidence
of increased transmission at this time.
All data are provisional and may be affected by reporting delays, incomplete country data or low
testing volumes. A few countries with high testing rates can disproportionately influence pooled
data. Further information is available under ‘Country notes’ and ‘Additional resources’
.
Outbreak of Salmonella Bovismorficians – Multi-country – 2026
• A multicountry outbreak of Salmonella Bovismorbificanshas been detected with about 50
confirmed cases in January to April 2026.
• All cases are adults, predominantly female. At least five cases have been hospitalised.
• Sprouted seeds/microgreens are identified as common source of infection in Ireland, Finland
and the UK.
• Five additional countries have identified closely related isolates in cases from the same period,
or observed an increase in this serotype, but without further information on food consumption
or travel history.
1. Influenza A(H5N1) – Multi-country
(World) – Monitoring human cases
Overview:
On 21 April 2026, Cambodia's Ministry of Health reported a new human case of avian influenza
A(H5N1) virus infection in a woman in her 60's from Romduol district, Svay Rieng province.
The patient is currently isolated in hospital and is receiving treatment. Epidemiological investigations
revealed that the patient had contact with poultry and that there had been sick and dead poultry
both in the household and in the village between 2 and 13 April 2026. On 21 April 2026, the National
Institute of Public Health confirmed infection with avian influenza A(H5N1). No additional information
is available at this time.
National and local authorities are actively investigating the event and implementing response
measures. As part of the response, close contacts of the case have received antiviral prophylaxis
(oseltamivir), and health education campaigns are ongoing in the affected villages.
This is the fourth human case reported in Cambodia this year. The most recent, previous case (in a
child) was reported on 31 March 2026. Information about the virus clade has not been reported for
the recent cases. Clade 2.3.2.1e has been circulating among birds in Cambodia and has been
detected in infected humans in the recent past. Overall, since 2003, Cambodia has reported 93
cases, including 52 deaths (CFR: 56%).
Summary:
Since 2003, there have been 998 human cases of avian influenza A(H5N1) infection worldwide*,
including 477 deaths (CFR: 48%). These cases have been reported in 25 countries (Australia
(exposure occurred in India), Azerbaijan, Bangladesh, Cambodia, Canada, Chile, China, Djibouti,
Ecuador, Egypt, India, Indonesia, Iraq, Laos, Mexico, Myanmar, Nepal, Nigeria, Pakistan, Spain,
Thailand, Türkiye, Viet Nam, the United Kingdom (UK), and the United States (US)). To date, no
sustained human-to-human transmission has been detected.
* This includes detections due to suspected environmental contamination, with no evidence of
infection, that were reported in 2022 and 2023 by Spain (two detections), the US (one), and the UK
(four, one of which was inconclusive). Human cases of A(H5) epidemiologically linked to A(H5N1)
outbreaks in poultry and dairy cattle in the US are included in the reported number of cases of
A(H5N1).
Acknowledgements: we gratefully acknowledge all data contributors, i.e. the authors and their
originating laboratories responsible for obtaining the specimens, and the submitting laboratories for
generating the genetic sequences and metadata and sharing via the GISAID Initiative.
ECDC assessment:
Sporadic human cases of different avian influenza A(H5) subtypes have previously been reported
around the world. Current virological evidence suggests that circulating A(H5N1) viruses retain
genetic characteristics consistent with avian-adapted influenza viruses. Despite the widespread
transmission of avian influenza viruses in animals, transmission to humans remains infrequent and
no sustained transmission between humans has been observed.
Based on the currently available information, the overall risk related to zoonotic influenza for the
general population in the EU/EEA is considered low.
Direct contact with birds and other infected animals, their secretions or a contaminated environment
is the most likely source of infection. Application of personal protective measures in people exposed
to infected animals or their environment can reduce the associated risk. The recent severe cases in
Asia and the Americas in children and people exposed to infected, sick or dead backyard poultry
underline the risk of unprotected contact with infected birds in backyard farm settings. This supports
the importance of using appropriate personal protective equipment.
Actions:
ECDC monitors avian influenza strains through its influenza surveillance programme and epidemic
intelligence activities in collaboration with the European Food Safety Authority (EFSA) and the EU
Reference Laboratory for Avian Influenza in order to identify significant changes in the virological
characteristics and epidemiology of the virus. Together with EFSA and the EU Reference Laboratory
for Avian Influenza, ECDC produces a quarterly updated avian influenza overview. The most recent
report was published in March 2026.
Last time this event was included in the Weekly CDTR: 1 April 2026
https://www.ecdc.europa.eu/sites/default/files/documents/2026-WCP-0021 Final.pdf