Comparative epidemiology of human infections with avian influenza A/H7N9 and H5N1 viruses in China: a population-based study of laboratory-confirmed cases

Cowling BJ, Jin L, Lau EH, Liao Q, Wu P, Jiang H, et al. Lancet. 2013 Jul 13;382(9887):129-37.

The novel influenza A H7N9 virus emerged recently in mainland China, whereas the influenza A H5N1 virus has infected people in China since 2003. Both infections are thought to be mainly zoonotic. We aimed to compare the epidemiological characteristics of the complete series of laboratory-confirmed cases of both viruses in mainland China so far.

An integrated database was constructed with information about demographic, epidemiological, and clinical variables of laboratory-confirmed cases of H7N9 (130 patients) and H5N1 (43 patients) that were reported to the Chinese Centre for Disease Control and Prevention until May 24, 2013. We described disease occurrence by age, sex, and geography, and estimated key epidemiological variables. We used survival analysis techniques to estimate the following distributions: infection to onset, onset to admission, onset to laboratory confirmation, admission to death, and admission to discharge.

The median age of the 130 individuals with confirmed infection with H7N9 was 62 years and of the 43 with H5N1 was 26 years. In urban areas, 74% of cases of both viruses were in men, whereas in rural areas the proportions of the viruses in men were 62% for H7N9 and 33% for H5N1. 75% of patients infected with H7N9 and 71% of those with H5N1 reported recent exposure to poultry. The mean incubation period of H7N9 was 3·1 days and of H5N1 was 3·3 days. On average, 21 contacts were traced for each case of H7N9 in urban areas and 18 in rural areas, compared with 90 and 63 for H5N1. The fatality risk on admission to hospital was 36% (95% CI 26-45) for H7N9 and 70% (56-83%) for H5N1.

The sex ratios in urban compared with rural cases are consistent with exposure to poultry driving the risk of infection--a higher risk in men was only recorded in urban areas but not in rural areas, and the increased risk for men was of a similar magnitude for H7N9 and H5N1. However, the difference in susceptibility to serious illness with the two different viruses remains unexplained, since most cases of H7N9 were in older adults whereas most cases of H5N1 were in younger people. A limitation of our study is that we compared laboratory-confirmed cases of H7N9 and H5N1 infection, and some infections might not have been ascertained.

Link to full text

MMLAP and other EU Projects

Health system analysis to support capacity development in response to the threat of pandemic influenza in Asia
Making society an active participant in water adaptation to global change
Public Participation in Developing a Common Framework for Assessment and Management of Sustainable Innovation
Engaging all of Europe in shaping a desirable and sustainable future
Expect the unexpected and know how to respond
Driving innovation in crisis management for European resilience
Effective communication in outbreak management: development of an evidence-based tool for Europe
Solutions to improve CBRNe resilience
Network for Communicable Disease Control in Southern Europe and Mediterranean Countries
Developing the framework for an epidemic forecast infrastructure
Strengthening of the national surveillance system for communicable diseases
Surveillance of vaccine preventable hepatitis
European monitoring of excess mortality for public health action
European network for highly infectious disease
Dedicated surveillance network for surveillance and control of vaccine preventable diseases in the EU
Modelling the spread of pandemic influenza and strategies for its containment and mitigation
Cost-effectiveness assessment of european influenza human pandemic alert and response strategies
Bridging the gap between science, stakeholders and policy makers
Promotion of immunization for health professionals in Europe
Towards inclusive research programming for sustainable food innovations
Addressing chronic diseases and healthy ageing across the life cycle
Medical ecosystem – personalized event-based surveillance
Studying the many and varied economic, social, legal and ethical aspects of the recent developments on the Internet, and their consequences for the individual and society at large
Get involved in the responsible marine research and innovation
Knowledge-based policy-making on issues involving science, technology and innovation, mainly based upon the practices in Parliamentary Technology Assessment
Assessment of the current pandemic preparedness and response tools, systems and practice at national, EU and global level in priority areas
Analysis of innovative public engagement tools and instruments for dynamic governance in the field of Science in Society
Public Engagement with Research And Research Engagement with Society
Computing Veracity – the Fourth Challenge of Big Data
Providing infrastructure, co-ordination and integration of existing clinical research networks on epidemics and pandemics
Promote vaccinations among migrant population in Europe
Creating mechanisms for effectively tackling the scientific and technology related challenges faced by society
Improve the quality of indoor air, keeping it free from radon
Improving respect of ethics principles and laws in research and innovation, in line with the evolution of technologies and societal concerns
Investigating how cities in the West securitise against global pandemics
Creating a structured dialogue and mutual learning with citizens and urban actors by setting up National Networks in 10 countries across Europe
Identifying how children can be change agents in the Science and Society relationship
Establishing an open dialogue between stakeholders concerning synthetic biology’s potential benefits and risks
Transparent communication in Epidemics: Learning Lessons from experience, delivering effective Messages, providing Evidence