Xu Xie

Seroprevalence to Avian Influenza A(H7N9) Virus Among Poultry Workers and the General Population in Southern China: A Longitudinal Study

BACKGROUND Confirmed cases of avian influenza A(H7N9) virus infection in humans continue to occur in mainland China. Few confirmed cases have occurred in poultry workers despite potentially higher rates of exposure. METHODS A serological survey was conducted in May and December 2013 in poultry market workers, and in March and September 2013 in the general population. Blood samples were collected and tested for antibodies to H7N9 and H5N1 viruses by hemagglutination inhibition (HI) assays. Multivariable analysis was employed to identify risk factors related to H7N9 infection indicated by serology among poultry workers. RESULTS In the poultry workers, 36 of 501 (7.2%) in May and 56 of 375 (14.9%) in December had HI antibody titers ≥1:160 to H7N9. Of 96 individuals who participated in both surveys, 52 (54.2%) workers had a ≥4-fold rise in H7N9 antibody titers from May to December. In a multivariable analysis, female sex (odds ratio [OR], 2.713; 95% confidence interval [CI], 1.098-6.705) and ≥10 years of occupational exposure (OR, 3.592; 95% CI, 1.246-10.354) were identified as risk factors for infection. Seroprevalence against H5N1 at ≥1:160 was low in May (4/501 [0.8%]) and December (3/375 [0.8%]). In the general population, 0 of 417 individuals in March and 0 of 408 individuals in September had antibody titers ≥1:160 to H7N9 or to H5N1. CONCLUSIONS Although none of the participants in our study had virologically confirmed H7N9 infection, the high proportion of poultry workers with serologic evidence of H7N9 infection between May and December 2013 suggests a substantial risk of mild H7N9 infections in this group, supporting stricter control measures in live poultry markets.

Short-term effects of meteorological factors on hand, foot and mouth disease among children in Shenzhen, China: Non-linearity, threshold and interaction.

BACKGROUND Various meteorological factors have been associated with hand, foot and mouth disease (HFMD) among children; however, fewer studies have examined the non-linearity and interaction among the meteorological factors. METHODS A generalized additive model with a log link allowing Poisson auto-regression and over-dispersion was applied to investigate the short-term effects daily meteorological factors on children HFMD with adjustment of potential confounding factors. RESULTS We found positive effects of mean temperature and wind speed, the excess relative risk (ERR) was 2.75% (95% CI: 1.98%, 3.53%) for one degree increase in daily mean temperature on lag day 6, and 3.93% (95% CI: 2.16% to 5.73%) for 1m/s increase in wind speed on lag day 3. We found a non-linear effect of relative humidity with thresholds with the low threshold at 45% and high threshold at 85%, within which there was positive effect, the ERR was 1.06% (95% CI: 0.85% to 1.27%) for 1 percent increase in relative humidity on lag day 5. No significant effect was observed for rainfall and sunshine duration. For the interactive effects, we found a weak additive interaction between mean temperature and relative humidity, and slightly antagonistic interaction between mean temperature and wind speed, and between relative humidity and wind speed in the additive models, but the interactions were not statistically significant. CONCLUSIONS This study suggests that mean temperature, relative humidity and wind speed might be risk factors of children HFMD in Shenzhen, and the interaction analysis indicates that these meteorological factors might have played their roles individually.

Three fatal cases of pandemic 2009 influenza A virus infection in Shenzhen are associated with cytokine storm

China had taken strict measures for pandemic 2009 H1N1 infection with enhanced surveillance and hospital isolation since April 2009. In Shenzhen, over 1200 confirmed cases of H1N1 infection were identified. Three young patients died of severe pneumonia. Among them, two boys developed neurological complications. Cytokine storm seemed an important cause.

Epidemiological Dynamics and Phylogeography of Influenza Virus in Southern China

BACKGROUND Understanding the epidemiological dynamics of influenza virus is central to surveillance and vaccine strain selection. It has been suggested that tropical and subtropical regions represent the global source of influenza epidemics. However, our understanding of the epidemiological dynamics of influenza virus in these regions is limited by a relative lack of long-term data. METHODS We analyzed epidemiological and virological data on influenza recorded over a period of 15 years from the metropolitan city of Shenzhen in subtropical southern China. We used wavelet analysis to determine the periodicity of influenza epidemics and molecular phylogeographic analysis to investigate the role of Shenzhen and southern China in the global evolution of influenza virus. RESULTS We show that southern China is unlikely to represent an epicenter of global influenza activity, because activity in Shenzhen is characterized by significant annual cycles, multiple viral introductions every year, limited persistence across epidemic seasons, and viruses that generally are not positioned on the trunk of the global influenza virus phylogeny. CONCLUSIONS We propose that novel influenza viruses emerge and evolve in multiple geographic localities and that the global evolution of influenza virus is complex and does not simply originate from a southern Chinese epicenter.

Vibrio parahaemolyticus, Southern Coastal Region of China, 2007–2012

We analyzed the prevalence and characteristics of Vibrio parahaemolyticus among patients with acute infectious diarrhea in the southern coastal region of China. V. parahaemolyticus was the leading cause of bacterial infectious diarrhea in this region during 2007–2012. Serotype O3:K6 strains were most common, followed by serotypes O4:K8 and O3:K29.

Economic evaluation of universal newborn hepatitis B vaccination in China

OBJECTIVE To estimate the long-term cost-effectiveness of universal newborn hepatitis B vaccination in China, an area of high endemicity. METHOD A decision tree was used to describe perinatal hepatitis B virus (HBV) transmission, early infection and impact of vaccination. A Markov model based on 1-year cycles was used to simulate these impacts for the lifetime of a cohort of 10,000,000 infants born in 2002 in China. We compared both cost and health outcomes for two strategies: universal newborn vaccination comprising a timely birth dose (HepB1) with a three-dose vaccination (HepB3) compared with no vaccination. Univariate and probabilistic sensitivity analyses using Monte Carlo simulations were performed to test parameter uncertainty. RESULTS Over the cohorts lifetime, 79,966 chronic infections, 37,553 cases of hepatocellular carcinoma (HCC) and 130,796 HBV related deaths would be prevented by universal infant vaccination. The prevalence of HBV infection is reduced by 76%. Over 743,000 life-years and 620,000 quality adjusted life years (QALYs) would be gained and there would be monetary benefits of more than 1 billion US dollars in medical care costs and lost productivity avoided. CONCLUSION The newborn vaccination programme for Hepatitis B in China both gains QALYs and saves medical care costs. It is important to ensure that timely and comprehensive vaccination programmes continue.

Seroprevalence of rubella in female migrant factory workers in Shenzhen, China.

BACKGROUND Rubella remains a common disease in Mainland China and is a major cause of severe birth defects from Congenital Rubella Syndrome (CRS). Rubella-containing vaccines were not included in Chinas National Expanded Program of Immunization (NEPI) until December 2007. In Shenzhen, women of childbearing age make up a large percentage of its migrant factory worker population. Understanding their immunity to rubella is critical in furthering efforts towards rubella vaccination programs. OBJECTIVES To investigate the seronegativity of rubella antibodies and evaluate potential associates of rubella immunity among female migrant factory workers in Shenzhen, China. SUBJECTS AND METHODS Serum samples were collected from 518 female migrant workers, aged 18-55, working in 44 randomly selected factories in Shenzhen, China during May through June of 2009. Samples were tested for Rubella Immunoglobulin G (IgG) using a commercial Enzyme-linked immunosorbant assay kit. Self-reported vaccination histories and socio-demographic information were also collected. RESULTS Of 518 female workers, 402 (77.6%) were immune to rubella. Significant differences in seronegativity were dependent on region of origin, being without a job contract, age group, marital status and seronegativity of measles. CONCLUSIONS Seroprevalence of antibodies to rubella in Shenzhen, China amongst female migrant workers is too low to provide immunity in the population. Given the high numbers of women of childbearing age amongst Shenzhen migrant factory workers coming from many provinces across China, local health authorities in Shenzhen should consider combining new rubella immunization programs with existing measles immunization efforts in this population.

Severe hand, foot and mouth disease in Shenzhen, South China: what matters most?

Case report data and a matched case-control study were used to investigate the epidemiological characteristics of hand, foot and mouth disease (HFMD) in children in Shenzhen, China between 2008 and 2011. Multivariate analyses were used to evaluate factors associated with severity of infection. Laboratory tests were performed to determine aetiological identification for samples from 163 severe and fatal cases as well as an outpatient-based HFMD sentinel surveillance system (n = 446). All identified EV71 belonged to sub-genotype C4a. No major changes in the CA16 and EV71 viruses were found until the end of 2011. Annual attack rates and the case-severity ratios (CSRs) rose from 0.82/1000 and 0.56/1000, respectively, in 2008 to 2.12/1000 and 6.13/1000 in 2011. The CSR was higher in migrants than in local residents. The adjusted odds ratio (OR) of having a severe attack for being a migrant was 2.45, having a fever >39°C (OR 5.77), visiting a private clinic (OR 2.65), longer time from symptom onset to diagnosis (OR 1.49), visiting a doctor (OR 1.51), early use of intramuscular pyrazolone (OR 3.36), early use of intravenous glucocorticoids (OR 2.28), or the combination of both (OR 3.75). The mortality and increasing case severity appears to be associated with socioeconomic factors including migration and is of worldwide concern.

Risk Factors for Vibrio parahaemolyticus Infection in a Southern Coastal Region of China

OBJECTIVES The objectives of the study were to identify dietary and medical risk factors for Vibrio parahaemolyticus (VP) infection in the coastal city Shenzhen in China. METHODS In April-October 2012, we conducted a case-control study in two hospitals in Shenzhen, China. Laboratory-confirmed VP cases (N = 83) were matched on age, sex, and other social factors to healthy controls (N = 249). Subjects were interviewed using a questionnaire on medical history; contact with seawater; clinical symptoms and outcome; travel history over the past week; and dietary history 3 days prior to onset. Laboratory tests were used to culture, serotype, and genotype VP strains. We used logistic regression to calculate the odds ratios for the association of VP infection with potential risk factors. RESULTS In multivariate analysis, VP infection was associated with having pre-existing chronic disease (adjusted odds ratio [aOR], 6.0; 95% confidence interval [CI], 1.5-23.7), eating undercooked seafood (aOR, 8.0; 95% CI, 1.3-50.4), eating undercooked meat (aOR, 29.1; 95% CI, 3.0-278.2), eating food from a street food vendor (aOR, 7.6; 95% CI, 3.3-17.6), and eating vegetable salad (aOR, 12.1; 95% CI, 5.2-28.2). CONCLUSIONS Eating raw (undercooked) seafood and meat is an important source of VP infection among the study population. Cross-contamination of VP in other food (e.g., vegetables and undercooked meat) likely plays a more important role. Intervention should be taken to lower the risks of cross-contamination with undercooked seafood/meat, especially targeted at people with low income, transient workers, and people with medical risk factors.

Influenza surveillance in Shenzhen, the largest migratory metropolitan city of China, 2006-2009

Shenzhen is one of the largest migratory metropolitan cities in China. A standardized influenza surveillance system has been operating in Shenzhen for several years. The objectives of the present study were to describe the epidemiology of influenza in Shenzhen and to assess the impact of pandemic H1N1 on influenza activity. An average rate of 71 cases of influenza-like illness (ILI)/1000 consultations was reported, which was greater than the rate in the preceding 3 years. Laboratory surveillance showed that the annual proportion of specimens positive for influenza was 25·4% in 2009, representing a significant increase over the proportions of 5·4%, 11·6% and 12·2% in 2006, 2007 and 2008, respectively. A total of 414 ILI outbreaks were reported in 2009, which was a marked increase compared to the previous 3 years. Influenza activity reached a record high in Shenzhen in 2009. Seasonal A/H3N2 was the dominant strain during the summer and was gradually replaced by pandemic H1N1. A semi-annual cycle for influenza circulation began to appear due to the emergence of pandemic H1N1.