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Influenza A(H7N9) - China - Monitoring human cases (ECDC/CDTR, May 7 2013)
[Source: European Centre for Disease Prevention and Control (ECDC), full PDF document: (LINK). Edited.]
COMMUNICABLE DISEASE THREATS REPORT
Week 18, 28 April-4 May 2013
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Influenza A(H7N9) - China - Monitoring human cases
Opening date: 31 March 2013 Latest update: 2 May 2013
Epidemiological summary
The influenza A viruses from the first three cases were non-subtypeable and were sent to the WHO Influenza Collaborating Centre at the Chinese Centre for Disease Control and Prevention (CCDC). The genetic comparison indicated that these cases were caused by a novel reassortant avian influenza virus with avian origin genes from both A(H7N9) and A(H9N2). No similar viruses have been seen before and A(H7N9) differs from A(H7) and A(H9) viruses that have been seen previously in Europe. No vaccine is currently available for this subtype of the influenza virus. Preliminary test results suggest that the virus is susceptible to the neuraminidase inhibitors (oseltamivir and zanamivir).
Since 31 March 2013, 128 cases of human infection with influenza A(H7N9) have been reported from eastern China and Taiwan:
Most cases have developed severe respiratory disease. Twenty six patients have died (case-fatality ratio=20%). The median age is 61 years with a range between four and 91 years; 36 of 128 patients are female.
The Chinese health authorities are responding to this public health event with enhanced surveillance, epidemiological and laboratory investigation and contact tracing. The animal health sector has intensified investigations into the possible sources and reservoirs of the virus. The authorities reported to the World Organisation for Animal Health (OIE) that avian influenza A(H7N9) was detected in samples from pigeons, chickens and ducks, and in environmental samples from live bird markets ('wet markets') in Shanghai, Jiangsu, Anhui and Zhejiang provinces. Authorities have closed markets and culled poultry in affected areas.
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ECDC assessment
The source and mode of transmission have not been confirmed. The outbreak is caused by a reassortant avian influenza virus with low pathogenicity for birds, hence it does not cause the signal 'die-offs' in poultry associated with highly pathogenic strains of avian influenza viruses. Genetic analyses of the isolates have shown changes which suggest that the H7N9 virus may have greater ability to infect mammalian species, including humans, than most other avian influenza viruses.
Pathogenicity for humans appears to be high and higher age appears to be a risk factor for disease.
The most likely scenario is that of A(H7N9) spreading undetected in poultry populations and occasionally infecting humans who have close contact with poultry or poultry products but this will have to be validated as further data become available.
At this time there is no evidence of any human-to-human transmission. Nearly 2 000 close contacts of confirmed cases are reported to have been followed up without evidence of person-to-person transmission.
There are three family cluster with four confirmed cases for which human-to-human transmission cannot be ruled out but where common exposure is the most likely explanation. An increasing incidence of sporadic cases and expansion of geographic spread in China and possibly neighbouring countries is expected over the coming weeks. Individual imported human cases to Europe cannot be ruled out and EU Member States need to prepare for detecting and diagnosing such cases. Critical developments that would change this assessment would be evidence of sustained human-to-human transmission and detection of avian influenza A(H7N9) in bird populations in Europe.
Actions
ECDC is closely monitoring developments and is continuously re-assessing the situation in collaboration with WHO, the US CDC, the Chinese CDC and other partners.
This epidemiological update does not change the conclusions and recommendations of the updated rapid risk assessment published on 12 April 2013. ECDC has published an epidemiological update on A(H7N9) on 29 April.
A case detection algorithm and an EU case definition has been developed and shared with EU Member states. The documents will also be published on the ECDC website in the coming days.
ECDC guidance for Supporting diagnostic preparedness for detection of avian influenza A(H7N9) viruses in Europe for laboratories was published on 24 April 2013.
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COMMUNICABLE DISEASE THREATS REPORT
Week 18, 28 April-4 May 2013
(?)
Influenza A(H7N9) - China - Monitoring human cases
Opening date: 31 March 2013 Latest update: 2 May 2013
Epidemiological summary
The influenza A viruses from the first three cases were non-subtypeable and were sent to the WHO Influenza Collaborating Centre at the Chinese Centre for Disease Control and Prevention (CCDC). The genetic comparison indicated that these cases were caused by a novel reassortant avian influenza virus with avian origin genes from both A(H7N9) and A(H9N2). No similar viruses have been seen before and A(H7N9) differs from A(H7) and A(H9) viruses that have been seen previously in Europe. No vaccine is currently available for this subtype of the influenza virus. Preliminary test results suggest that the virus is susceptible to the neuraminidase inhibitors (oseltamivir and zanamivir).
Since 31 March 2013, 128 cases of human infection with influenza A(H7N9) have been reported from eastern China and Taiwan:
- Zhejiang (46),
- Shanghai (33),
- Jiangsu (27),
- Henan (4),
- Anhui (4),
- Beijing (1),
- Shandong (2),
- Fujian (3),
- Hunan (2),
- Jiangxi (5) and
- Taiwan (1).
Most cases have developed severe respiratory disease. Twenty six patients have died (case-fatality ratio=20%). The median age is 61 years with a range between four and 91 years; 36 of 128 patients are female.
The Chinese health authorities are responding to this public health event with enhanced surveillance, epidemiological and laboratory investigation and contact tracing. The animal health sector has intensified investigations into the possible sources and reservoirs of the virus. The authorities reported to the World Organisation for Animal Health (OIE) that avian influenza A(H7N9) was detected in samples from pigeons, chickens and ducks, and in environmental samples from live bird markets ('wet markets') in Shanghai, Jiangsu, Anhui and Zhejiang provinces. Authorities have closed markets and culled poultry in affected areas.
(?)
ECDC assessment
The source and mode of transmission have not been confirmed. The outbreak is caused by a reassortant avian influenza virus with low pathogenicity for birds, hence it does not cause the signal 'die-offs' in poultry associated with highly pathogenic strains of avian influenza viruses. Genetic analyses of the isolates have shown changes which suggest that the H7N9 virus may have greater ability to infect mammalian species, including humans, than most other avian influenza viruses.
Pathogenicity for humans appears to be high and higher age appears to be a risk factor for disease.
The most likely scenario is that of A(H7N9) spreading undetected in poultry populations and occasionally infecting humans who have close contact with poultry or poultry products but this will have to be validated as further data become available.
At this time there is no evidence of any human-to-human transmission. Nearly 2 000 close contacts of confirmed cases are reported to have been followed up without evidence of person-to-person transmission.
There are three family cluster with four confirmed cases for which human-to-human transmission cannot be ruled out but where common exposure is the most likely explanation. An increasing incidence of sporadic cases and expansion of geographic spread in China and possibly neighbouring countries is expected over the coming weeks. Individual imported human cases to Europe cannot be ruled out and EU Member States need to prepare for detecting and diagnosing such cases. Critical developments that would change this assessment would be evidence of sustained human-to-human transmission and detection of avian influenza A(H7N9) in bird populations in Europe.
Actions
ECDC is closely monitoring developments and is continuously re-assessing the situation in collaboration with WHO, the US CDC, the Chinese CDC and other partners.
This epidemiological update does not change the conclusions and recommendations of the updated rapid risk assessment published on 12 April 2013. ECDC has published an epidemiological update on A(H7N9) on 29 April.
A case detection algorithm and an EU case definition has been developed and shared with EU Member states. The documents will also be published on the ECDC website in the coming days.
ECDC guidance for Supporting diagnostic preparedness for detection of avian influenza A(H7N9) viruses in Europe for laboratories was published on 24 April 2013.
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