[Epidemiological characteristics of infection for close contacts of pandemic (H1N1) 2009 in Beijing].

OBJECTIVE: To examine the epidemiological characteristics of infection for close contacts of pandemic (H1N1) 2009 and to provide scientific evidence for preparedness and response for the next pandemic. METHODS: A total of 613 index cases with clear information of close contacts and their 7099 close contacts, determined between May 16 and September 15, 2009, were included in this study. Based on data of epidemiological investigation, sampling and test of index cases and close contacts, the characteristics of infection for close contacts were described. RESULTS: 56.8% (348/613) of the index cases were male, and 43.2% (265/613) were female, and the median age was 20 years (range: 1 - 75 years). 49.6% (3518/7099) of the close contacts were male, and 49.5% (3514/7099) were female, but the sex information of 0.9% (67/7099) could not be recorded. The median age of the close contacts was 27 years (range: 0 - 99 years). 2.4% (167/7099) of close contacts were infected. The attack rates decreased with increasing age of close contacts (χ()2 = 27.87, P < 0.001), and were significantly different between various contact patterns of close contacts (χ()2 = 109.76, P < 0.001). 14.4% of the infected close contacts were asymptomatic. For close contacts with symptomatic infection, virus could be shed 4.5 days before illness onset, and the median generation time was 2.4 days. CONCLUSION: The attack rate of close contacts was very low; and the attack rates were different between various ages and contact patterns of close contacts. In this series 14% of cases with pandemic (H1N1) 2009 were asymptomatic. The symptomatic cases might have infectivity 1 day earlier before illness onset.

[Safety and epidemiological effects of the first China-made mass A (H1N1) influenza vaccination].

OBJECTIVE: To evaluate the safety and epidemiological effects on the first mass vaccination program, using the China-made A (H1N1) influenza vaccine. METHODS: Descriptive epidemiology and cohort study design were used to assess the influenza A H1N1 vaccine on its safety and epidemiological effects. RESULTS: 95 244 subjects were immunized with A (H1N1) influenza vaccine. 193 adverse events were reported through AEFI Management System, with the Reported rates of AEFI as 2.03‰. Most of the adverse events (137/193, 71.0%) happened during the first 24 hours after immunization was carried out. Of 81 adverse reactions confirmed to be related to immunization, with 78 (96.3%) showed mild reactions. No Guillain-Barre Syndrome related to vaccination was reported through the AEFI Management System. The epidemiological protection rate of A (H1N1) vaccine could reach 80.9% when the coverage was not considered. CONCLUSION: The A (H1N1) influenza vaccine showed a similar safety profile to seasonal flu vaccine. The vaccine demonstrated a good epidemiological effects against A (H1N1) influenza virus infection.

Severe acute respiratory syndrome--retrospect and lessons of 2004 outbreak in China.

OBJECTIVE: To summarize lessons learned from an outbreak of severe acute respiratory syndrome (SARS) in China during the spring of 2004. METHODS: Data of SARS cases were officially reported by Beijing Municipal Center for Disease Control and Prevention (BCDC) and Anhui Provincial Center for Disease Control and Prevention (APCDC) and results of epidemiological investigations were collected and analyzed. RESULTS: Three generations of 11 cases of SARS were identified during the outbreak. Initial two cases were most likely to be infected in Diarrhea Virus Laboratory of National Institute of Virology, China Centers for Disease Control and Prevention and main mode of transmission was direct contact with SARS patients. Delay in detecting initial case resulted in spread of the illness at hospitals and communities with two generations of secondary cases. CONCLUSIONS: SARS outbreak in 2004 has yielded following lessons for public health globally. (1) Lab bio-safety programs should be made and should be strictly abided by. Studies in highly pathogenic viruses such as SARS coronavirus should be utmost cautious. (2) Management systems of occupational exposure to virus and disease surveillance need to be strengthened to take all risk factors into account so as to detect potential patients with infectious disease as early as possible.

[Analysis on the epidemiological features and the transmission of an imported severe acute respiratory syndrome case in Beijing].

OBJECTIVE: To explore the characteristics of severe acute respiratory syndrome (SARS) transmission in the population base on analyzing the first imported case and the chains of transmission. METHODS: For the first imported SARS case and cases who were transmitted by the index case, epidemiological investigations were conducted using the guidelines for surveillance and case investigation issued by the Ministry of Health. Data as the date of onset of symptoms, date of hospitalization, contact history etc. for each of the cases and their close contacts were collected and analyzed. RESULTS: The first imported SARS case introduced to Beijing had infected 9 people within the family and at the hospital, with two of whom died of the same disease. The incubation period for that index case was 4 days, and that for the cases considered to be the secondary and tertiary generations were 7 and 8 days, respectively. The shorter the incubation period, the longer the fever would last and clinically more severe. CONCLUSION: One of the epidemiological characteristics of SARS in Beijing was noticed that the disease clustered in families and hospitals. Infection through droplets and close contact has been viewed as the primary mode of transmission.