Journal
BMJ-BRITISH MEDICAL JOURNAL
Volume 346, Issue -, Pages -Publisher
BMJ PUBLISHING GROUP
DOI: 10.1136/bmj.f3693
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Funding
- US National Institutes of Health (Comprehensive International Program for Research on AIDS) [U19 AI51915]
- China-US collaborative program on emerging and re-emerging infectious diseases
- Chinese Ministry of Science and Technology [2012 ZX10004-201]
- Harvard Center for Communicable Disease Dynamics from the National Institute of General Medical Sciences [U54 GM088558]
- Research Fund for the Control of Infectious Disease, Food, and Health Bureau (government of the Hong Kong Special Administrative Region)
- Hong Kong University [AoE/M-12/06]
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Objective To characterise the complete case series of influenza A/H7N9 infections as of 27 May 2013, detected by China's national sentinel surveillance system for influenza-like illness. Design Case series. Setting Outpatient clinics and emergency departments of 554 sentinel hospitals across 31 provinces in mainland China. Cases Infected individuals were identified through cross-referencing people who had laboratory confirmed A/H7N9 infection with people detected by the sentinel surveillance system for influenza-like illness, where patients meeting the World Health Organization's definition of influenza-like illness undergo weekly surveillance, and 10-15 nasopharyngeal swabs are collected each week from a subset of patients with influenza-like illness in each hospital for virological testing. We extracted relevant epidemiological data from public health investigations by the Centers for Disease Control and Prevention at the local, provincial, and national level; and clinical and laboratory data from chart review. Main outcome measure Epidemiological, clinical, and laboratory profiles of the case series. Results Of 130 people with laboratory confirmed A/H7N9 infection as of 27 May 2013, five (4%) were detected through the sentinel surveillance system for influenza-like illness. Mean age was 13 years (range 2-26), and none had any underlying medical conditions. Exposure history, geographical location, and timing of symptom onset of these five patients were otherwise similar to the general cohort of laboratory confirmed cases so far. Only two of the five patients needed hospitalisation, and all five had mild or moderate disease with an uneventful course of recovery. Conclusion Our findings support the existence of a clinical iceberg phenomenon in influenza A/H7N9 infections, and reinforce the need for vigilance to the diverse presentation that can be associated with A/H7N9 infection. At the public health level, indirect evidence suggests a substantial proportion of mild disease in A/H7N9 infections.
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