Open Access Highly Accessed Research article

Accuracy of epidemiological inferences based on publicly available information: retrospective comparative analysis of line lists of human cases infected with influenza A(H7N9) in China

Eric HY Lau1, Jiandong Zheng2, Tim K Tsang1, Qiaohong Liao2, Bryan Lewis3, John S Brownstein45, Sharon Sanders6, Jessica Y Wong1, Sumiko R Mekaru4, Caitlin Rivers3, Peng Wu1, Hui Jiang2, Yu Li2, Jianxing Yu2, Qian Zhang2, Zhaorui Chang2, Fengfeng Liu2, Zhibin Peng2, Gabriel M Leung1, Luzhao Feng2, Benjamin J Cowling1* and Hongjie Yu2*

Author Affiliations

1 School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, Special Administrative Region, China

2 Division of Infectious Disease, Key Laboratory of Surveillance and Early-warning on Infectious Disease, Chinese Center for Disease Control and Prevention, Beijing, China

3 Network Dynamics and Simulation Science Laboratory, Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA, USA

4 Informatics Program, Boston Children’s Hospital, Boston, MA, USA

5 Department of Pediatrics, Harvard Medical School, Boston, MA, USA

6 FluTrackers International Charity, Florida 32789, USA

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BMC Medicine 2014, 12:88  doi:10.1186/1741-7015-12-88

Published: 28 May 2014

Abstract

Background

Appropriate public health responses to infectious disease threats should be based on best-available evidence, which requires timely reliable data for appropriate analysis. During the early stages of epidemics, analysis of ‘line lists’ with detailed information on laboratory-confirmed cases can provide important insights into the epidemiology of a specific disease. The objective of the present study was to investigate the extent to which reliable epidemiologic inferences could be made from publicly-available epidemiologic data of human infection with influenza A(H7N9) virus.

Methods

We collated and compared six different line lists of laboratory-confirmed human cases of influenza A(H7N9) virus infection in the 2013 outbreak in China, including the official line list constructed by the Chinese Center for Disease Control and Prevention plus five other line lists by HealthMap, Virginia Tech, Bloomberg News, the University of Hong Kong and FluTrackers, based on publicly-available information. We characterized clinical severity and transmissibility of the outbreak, using line lists available at specific dates to estimate epidemiologic parameters, to replicate real-time inferences on the hospitalization fatality risk, and the impact of live poultry market closure.

Results

Demographic information was mostly complete (less than 10% missing for all variables) in different line lists, but there were more missing data on dates of hospitalization, discharge and health status (more than 10% missing for each variable). The estimated onset to hospitalization distributions were similar (median ranged from 4.6 to 5.6 days) for all line lists. Hospital fatality risk was consistently around 20% in the early phase of the epidemic for all line lists and approached the final estimate of 35% afterwards for the official line list only. Most of the line lists estimated >90% reduction in incidence rates after live poultry market closures in Shanghai, Nanjing and Hangzhou.

Conclusions

We demonstrated that analysis of publicly-available data on H7N9 permitted reliable assessment of transmissibility and geographical dispersion, while assessment of clinical severity was less straightforward. Our results highlight the potential value in constructing a minimum dataset with standardized format and definition, and regular updates of patient status. Such an approach could be particularly useful for diseases that spread across multiple countries.

Keywords:
Epidemiological monitoring; Line list; Infectious disease outbreak; Influenza A virus; H7N9 subtype