Skip directly to site content Skip directly to page options Skip directly to A-Z link Skip directly to A-Z link Skip directly to A-Z link
Volume 21, Number 5—May 2015

Detecting Spread of Avian Influenza A(H7N9) Virus Beyond China

Alexander J. MillmanComments to Author , 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
Author affiliations: Author affiliations: Centers for Disease Control and Prevention (CDC), Atlanta, Georgia, USA (A.J. Millman, F. Havers, A.D. Iuliano, C.T. Davis, R.C. Donis, M.-A. Widdowson); CDC, Phnom Penh, Cambodia (B. Sar); Ministry of Health, Phnom Penh (L. Sovan); National Institute of Public Health, Phnom Penh (S. Chin); CDC, Vientiane, Laos (A.L. Corwin); National Center for Laboratory Epidemiology, Vientiane (P. Vongphrachanh); Ministry of Agriculture and Forestry, Vientiane (B. Douangngeun); Thailand Ministry of Public Health–CDC Collaboration, Nonthaburi, Thailand (K.A. Lindblade); National Institute of Health, Nonthaburi (M. Chittaganpitch); Ministry of Agriculture and Cooperatives, Bangkok, Thailand (V. Kaewthong); CDC, Hanoi, Vietnam (J.C. Kile); Ministry of Health, Hanoi (H.T. Nguyen); Ministry of Agriculture and Rural Development, Hanoi (D.V. Pham)

Main Article

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
SARI and ILI surveillance systems should detect with equal efficacy
Disease severity
Critical and fatal (60%)
Most are critical; mild infections reported in children
Hospital-based platforms would be most likely to detect cases
Patient age, y
Surveillance systems that do not cover older adults may not detect case
December–March (average)
Most cases in 2nd wave occurred December–March 2013–2014
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)
Primarily rural (farm)
Primarily urban (LBM)
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
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
Surveillance systems will probably detect sporadic cases that have identifiable poultry exposures
History of poultry exposure
Animal surveillance is critical for detection in poultry and assisting with targeting control measures
Pathogenicity in chickens
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.

Main Article

Page created: April 17, 2015
Page updated: April 17, 2015
Page reviewed: April 17, 2015
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.