Volume 21, Number 5—May 2015
Perspective
Detecting Spread of Avian Influenza A(H7N9) Virus Beyond China
Alexander J. Millman
, Fiona Havers, A. Danielle Iuliano, C. Todd Davis, Borann Sar, Ly Sovann, Savuth Chin, Andrew L. Corwin, Phengta Vongphrachanh, Bounlom Douangngeun, Kim A. Lindblade, Malinee Chittaganpitch, Viriya Kaewthong, James C. Kile, Hien T. Nguyen, Dong V. Pham, Ruben O. Donis, and Marc-Alain Widdowson
, Fiona Havers, A. Danielle Iuliano, C. Todd Davis, Borann Sar, Ly Sovann, Savuth Chin, Andrew L. Corwin, Phengta Vongphrachanh, Bounlom Douangngeun, Kim A. Lindblade, Malinee Chittaganpitch, Viriya Kaewthong, James C. Kile, Hien T. Nguyen, Dong V. Pham, Ruben O. Donis, and Marc-Alain Widdowson
Table 1
Characteristics of influenza A(H5N1) and A(H7N9) infection and implications for surveillance system detection of A(H7N9) in humans and animals*
| Characteristic | A(H5N1) | A(H7N9) | Reference | Surveillance system implications for A(H7N9) detection |
|---|---|---|---|---|
| Clinical signs and symptoms |
Fever, cough, pneumonia, respiratory failure |
Fever, cough, pneumonia, respiratory failure |
(1,4) |
SARI and ILI surveillance systems should detect with equal efficacy |
| Disease severity |
Critical and fatal (60%) |
Most are critical; mild infections reported in children |
(4) |
Hospital-based platforms would be most likely to detect cases |
| Patient age, y |
<20 |
>60 |
(4) |
Surveillance systems that do not cover older adults may not detect case |
| Seasonality |
December–March (average) |
Most cases in 2nd wave occurred December–March 2013–2014 |
(3) |
Surveillance will be more likely to detect a case when the virus in circulating; however, additional data are needed to establish the seasonality of A(H7N9) |
| Geography |
Primarily rural (farm) |
Primarily urban (LBM) |
(4) |
Surveillance systems that do not cover visitors to LBMs may be unable to detect cases |
| Transmissibility from poultry or environment to humans |
Appears low |
Appears moderate |
(10) |
Surveillance systems should assess for poultry or environmental exposures, and known exposures should prompt testing in suspected cases of avian influenza |
| Person-to-person transmission |
Appears uncommon |
Appears uncommon |
(1,11) |
Surveillance systems will probably detect sporadic cases that have identifiable poultry exposures |
| History of poultry exposure |
Common |
Common |
(4) |
Animal surveillance is critical for detection in poultry and assisting with targeting control measures |
| Pathogenicity in chickens |
High |
Low |
(5,11) |
Infection with A(H7N9) does not appear to cause disease in poultry. Surveillance for detecting A(H7N9) in poultry requires targeted risk assessment and active testing. |
| Effects in wild bird species | Detected in wild bird species | Limited data | (11–13) | Poultry surveillance directed at either back-yard farms or commercial poultry farms (depending on prevalence) and LBMs should be sufficient to detect cases |
*ILI, influenza-like illness; LBM, live-bird market; SARI, severe acute respiratory infection.
Page created: April 17, 2015
Page updated: April 17, 2015
Page reviewed: April 17, 2015
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