A meta-transcriptomic study of mosquito virome and blood feeding patterns at the human-animal-environment interface in Guangdong Province, China.

Mosquitoes are a formidable reservoir of viruses and important vectors of zoonotic pathogens. Blood-fed mosquitoes have been utilized to determine host infection status, overcoming the difficulties associated with sampling from human and animal populations. Comprehensive surveillance of potential pathogens at the interface of humans, animals, and the environment is currently an accredited method to provide an early warning of emerging or re-emerging infectious diseases and to proactively respond to them. Herein we performed comprehensive sampling of mosquitoes from seven habitats (residential areas, hospital, airplane, harbor, zoo, domestic sheds, and forest park) across five cities in Guangdong Province, China. Our aim was to characterize the viral communities and blood feeding patterns at the human-animal-environment interface and analyze the potential risk of cross-species transmission using meta-transcriptomic sequencing. 1898 female adult mosquitoes were collected, including 1062 Aedes and 836 Culex mosquitoes, of which approximately 12% (n = 226) were satiated with blood. Consequently, 101 putative viruses were identified, which included DNA and RNA viruses, and positive-stranded RNA viruses (+ssRNA) were the most abundant. According to viral diversity analysis, the composition of the viral structure was highly dependent on host species, and Culex mosquitoes showed richer viral diversity than Aedes mosquitoes. Although the virome of mosquitoes from different sampling habitats showed an overlap of 39.6%, multiple viruses were specific to certain habitats, particularly at the human-animal interface. Blood meal analysis found four mammals and one bird bloodmeal source, including humans, dogs, cats, poultry, and rats. Further, the blood feeding patterns of mosquitoes were found to be habitat dependent, and mosquitoes at the human-animal interface and from forests had a wider choice of hosts, including humans, domesticated animals, and wildlife, which in turn considerably increases the risk of spillover of potential zoonotic pathogens. To summarize, we are the first to investigate the virome of mosquitoes from multiple interfaces based on the One Health concept. The characteristics of viral community and blood feeding patterns of mosquitoes at the human-animal-environment interface were determined. Our findings should support surveillance activities to identify known and potential pathogens that are pathogenic to vertebrates.

Collaboration between meteorology and public health: Predicting the dengue epidemic in Guangzhou, China, by meteorological parameters.

Background: Dengue has become an increasing public health threat around the world, and climate conditions have been identified as important factors affecting the transmission of dengue, so this study was aimed to establish a prediction model of dengue epidemic by meteorological methods. Methods: The dengue case information and meteorological data were collected from Guangdong Provincial Center for Disease Prevention and Control and Guangdong Meteorological Bureau, respectively. We used spatio-temporal analysis to characterize dengue epidemics. Spearman correlation analysis was used to analyze the correlation between lagged meteorological factors and dengue fever cases and determine the maximum lagged correlation coefficient of different meteorological factors. Then, Generalized Additive Models were used to analyze the non-linear influence of lagged meteorological factors on local dengue cases and to predict the number of local dengue cases under different weather conditions. Results: We described the temporal and spatial distribution characteristics of dengue fever cases and found that sporadic single or a small number of imported cases had a very slight influence on the dengue epidemic around. We further created a forecast model based on the comprehensive consideration of influence of lagged 42-day meteorological factors on local dengue cases, and the results showed that the forecast model has a forecast effect of 98.8%, which was verified by the actual incidence of dengue from 2005 to 2016 in Guangzhou. Conclusion: A forecast model for dengue epidemic was established with good forecast effects and may have a potential application in global dengue endemic areas after modification according to local meteorological conditions. High attention should be paid on sites with concentrated patients for the control of a dengue epidemic.

An occupational risk of hepatitis E virus infection in the workers along the meat supply chains in Guangzhou, China.

Hepatitis E virus (HEV) causes infections in humans and animals. HEV have been identified in pig farms, markets and swine workers, but studies with parallel observations along the poultry and pork supply chains remains limited. This study aimed to characterize HEV infection risks in workers along the meat supply chain. Two rounds of cross-sectional surveys were performed among swine and poultry workers in pig and poultry farms, slaughterhouses, wholesale and retail live poultry markets, live pig markets and pork markets. Human sera from the workers and the general population were collected and tested for HEV specific IgM/IgG antibodies by commercial indirect-ELISA test kits. Risk factors of HEV seropositivity associated with different occupational settings were identified using logistic regression. 47.0% (156/332) of the swine workers and 40.2% (119/296) of the poultry workers were seropositive, compared to 26.1% (35/134) in the general population. Multivariable analysis showed that human HEV infection risk increased along the pork supply chain, with the highest risk at pig slaughterhouses (adjusted OR = 3.19, 95% CI = 1.49-6.88) and pork markets (adjusted OR = 2.02, 95% CI = 1.04-3.97), but no significant higher risk was observed among poultry workers. Swine occupational exposure is associated with HEV infection, especially in workers in pig slaughterhouses and pork markets. Strengthening control measures in these settings is important for HEV control and long term HEV elimination.

Genomic characterization of Wenzhou mammarenavirus detected in wild rodents in Guangzhou City, China.

Wenzhou mammarenavirus (WENV) is a zoonotic pathogen newly discovered in east and southeast Asia. WENV has been found in wild rodent animals around the world while its standing is barely understood in Guangzhou city, where is known as a region of outbreak hotspot for zoonotic emerging infectious diseases. To investigate the prevalence and genomic characteristics of mammarenavirus in Guangzhou City, lung tissue samples from wild rodent species were collected from five districts of Guangzhou City in the year 2015 and 2016. The viral RNA was extracted and then subjected to mammarenavirus-specific PCR. The result revealed approximately 1.0% (3/306) nucleic acid positivity for lung tissue samples obtained from three rodent species: Mus musculus, Rattus flavipectus, and Rattus norvegicus. Viral metagenomic sequencing of three samples was then carried out and two full segment L and three full segment S sequences were obtained. Phylogenetics analysis indicated the sequences of the new mammarenavirus strain have 76.2% - 94.4% similarity to known WENV encoded genes, with the highest similarity to the WENV 9-24 strain. Population structure analysis grouped all known WENV into seven lineages, and this WENV Guangzhou strain was grouped with WENV 9-24 as well. Though the seroprevalence result was not available, our data provides the first nucleic acid evidence of circulating WENV in Guangzhou city, and it suggested WENV had a broader host tropism than previously known.

A Comparative Study of Associated Microbiota Between Pig Farm and Pig Slaughterhouse in Guangdong, China.

The goal of this study was to compare the microbiota in different pig-present settings in China. Bioaerosol samples from pig farms and slaughterhouses and nasal samples from pig farmers and slaughterhouse workers were collected in Guangdong, southern China. The bacterial genomic DNA was isolated and subjected to 16S sequencing. The data were analyzed using QIIME2 with the DADA2 pipeline. A total of 14,923,551 clean reads and 2785 operational taxonomic units (OTUs) were obtained, which were mostly grouped into 4 phyla (Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria) and 220 families. The microbiota richness of nasal samples in pig-present workers was higher than that of bioaerosols collected in the vicinity of the pig enclosures. There were 31.7% (620/1954) shared OTUs between pig farm bioaerosols and pig farmers which was higher than that between pig slaughterhouses and slaughterhouse workers (23.4%, 364/1553) (p < 0.001). Acinetobacter and Pseudomonas were the most abundant in pig-present bioaerosols, and Staphylococcus, Pseudomonas, and Corynebacterium were dominant bacterial genus in pig farmers. The bacterial patterns are also specific to the location of sample collected. The results suggest that bioaerosol microbiota interact with human nasal microbes in the vicinity of the pig farm enclosures, providing the basis for further analysis of microbial transmission across hosts in pig-present settings.

Distribution of the COVID-19 epidemic and correlation with population emigration from Wuhan, China.

BACKGROUND: The ongoing new coronavirus pneumonia (Corona Virus Disease 2019, COVID-19) outbreak is spreading in China, but it has not yet reached its peak. Five million people emigrated from Wuhan before lockdown, potentially representing a source of virus infection. Determining case distribution and its correlation with population emigration from Wuhan in the early stage of the epidemic is of great importance for early warning and for the prevention of future outbreaks. METHODS: The official case report on the COVID-19 epidemic was collected as of January 30, 2020. Time and location information on COVID-19 cases was extracted and analyzed using ArcGIS and WinBUGS software. Data on population migration from Wuhan city and Hubei province were extracted from Baidu Qianxi, and their correlation with the number of cases was analyzed. RESULTS: The COVID-19 confirmed and death cases in Hubei province accounted for 59.91% (5806/9692) and 95.77% (204/213) of the total cases in China, respectively. Hot spot provinces included Sichuan and Yunnan, which are adjacent to Hubei. The time risk of Hubei province on the following day was 1.960 times that on the previous day. The number of cases in some cities was relatively low, but the time risk appeared to be continuously rising. The correlation coefficient between the provincial number of cases and emigration from Wuhan was up to 0.943. The lockdown of 17 cities in Hubei province and the implementation of nationwide control measures efficiently prevented an exponential growth in the number of cases. CONCLUSIONS: The population that emigrated from Wuhan was the main infection source in other cities and provinces. Some cities with a low number of cases showed a rapid increase in case load. Owing to the upcoming Spring Festival return wave, understanding the risk trends in different regions is crucial to ensure preparedness at both the individual and organization levels and to prevent new outbreaks.

Risk assessment and genomic characterization of Zika virus in China and its surrounding areas.

BACKGROUND: Zika virus (ZIKV) has emerged as a global pathogen causing significant public health concerns. China has reported several imported cases where ZIKV were carried by travelers who frequently travel between China and ZIKV-endemic regions. To fully characterize the ZIKV strains isolated from the cases reported in China and assess the risk of ZIKV transmission in China, comprehensive phylogenetic and genetic analyses were performed both on all ZIKV sequences of China and on a group of scientifically selected ZIKV sequences reported in some of the top interested destinations for Chinese travelers. METHODS: ZIKV genomic sequences were retrieved from the National Center for Biotechnology Information database through stratified sampling. Recombination event detection, maximum likelihood (ML) phylogenetic analysis, molecular clock analysis, selection pressure analysis, and amino acid substitution analysis were used to reconstruct the epidemiology and molecular transmission of ZIKV. RESULTS: The present study investigated 18 ZIKV sequences from China and 70 sequences from 16 selected countries. Recombination events rarely happens in all ZIKV Asian lineage. ZIKV genomes were generally undergone episodic positive selection (17 sites), and only one site was under pervasive positive selection. All ZIKV imported into China were Asian lineage and were assigned into two clusters: Venezuela-origin (cluster A) and Samoa-origin cluster (cluster B) with common ancestor from French Polynesia. The time of most recent common ancestors of Cluster A dated to approximately 2013/11 (95% highest posterior density [HPD] 2013/06, 2014/03) and cluster B dated to 2014/08 (95% HPD 2014/02, 2015/01). Cluster B is more variable than Cluster A in comparison with other clusters, but no varied site of biological significance was revealed. ZIKV strains in Southeast Asia countries are independent from strains in America epidemics. CONCLUSIONS: The genetic evolution of ZIKV is conservative. There are two independent introductions of ZIKV into China and China is in danger of autochthonous transmission of ZIKV because of high-risk surrounding areas. Southeast Asia areas have high risk of originating the next large-scale epidemic ZIKV strains.

Transmission risk of avian influenza virus along poultry supply chains in Guangdong, China.

OBJECTIVES: Avian influenza viruses (AIVs) poise significant risk to human health and the poultry industry. We evaluated the transmission risk along the poultry supply chain. METHODS: During October 2015 and July 2016, four rounds of cross-sectional surveys were performed to characterize AIV spread in farms, transport vehicles, slaughterhouses, wholesale and retail live poultry markets (LPMs). Poultry cloacal and oral swabs, environmental swabs, bioaerosol samples and human sera were collected. Poultry and environmental samples were tested for AIVs by rRT-PCR, further subtyped by next generation sequencing. Previous human H9N2 infections were identified by hemagglutination inhibition and microneutralization tests. Logistic regression was fitted to compare AIV transmission risk in different settings. RESULTS: AIVs was detected in 23.9% (424/1771) of the poultry and environmental samples. AIV detection rates in farms, transport vehicles, wholesale and retail LPMs were 4.5%, 11.1%, 30.3% and 51.2%, respectively. 5.2%, 8.3% and 12.8% of the poultry workers were seropositive in farms, wholesale and retail LPMs, respectively. The regression analysis showed that virus detection and transmission risk to human increased progressively along the poultry supply chain. CONCLUSIONS: Strengthening control measures at every level along the poultry supply chain, using a one health approach, is crucial to control AIV circulation.

Clinical indices and mortality of hospitalized avian influenza A (H7N9) patients in Guangdong, China.

BACKGROUND: Six epidemic waves of human infection with avian influenza A (H7N9) virus have emerged in China with high mortality. However, study on quantitative relationship between clinical indices in ill persons and H7N9 outcome (fatal and non-fatal) is still unclear. A retrospective cohort study was conducted to collect laboratory-confirmed cases with H7N9 viral infection from 2013 to 2015 in 23 hospitals across 13 cities in Guangdong Province, China. METHODS: Multivariable logistic regression model and classification tree model analyses were used to detect the threshold of selected clinical indices and risk factors for H7N9 death. The receiver operating characteristic curve (ROC) and analyses were used to compare survival and death distributions and differences between indices. A total of 143 cases with 90 survivors and 53 deaths were investigated. RESULTS: Average age (Odds Ratio (OR) = 1.036, 95% Confidence Interval (CI) = 1.016-1.057), interval days between dates of onset and confirmation (OR = 1.078, 95% CI = 1.004-1.157), interval days between onset and oseltamivir treatment (OR = 5.923, 95% CI = 1.877-18.687), body temperature (BT) (OR = 3.612, 95% CI = 1.914-6.815), white blood cell count (WBC) (OR = 1.212, 95% CI = 1.092-1.346) were significantly associated with H7N9 death after adjusting for confounders. The chance of death from H7N9 infection was 80.0% if BT was over 38.1 °C, and chance of death is 67.4% if WBC count was higher than 9.5 (10/L). Only 27.1% of patients who began oseltamivir treatment less than 9.5 days after disease onset died, compared to 68.8% of those who started treatment more than 15.5 days after onset. CONCLUSIONS: The intervals between date of onset and confirmation of diagnosis, between date of onset to oseltamivir treatment, age, BT and WBC are found to be the best predictors of H7N9 mortality.

Field evaluation of two commercial RT-rtPCR assays for porcine reproductive and respiratory syndrome virus detection using sera from ill and healthy pigs, China.

Porcine reproductive and respiratory syndrome virus (PRRSV) is a highly contagious respiratory virus causing severe morbidity in pigs worldwide. Control strategies for PRRSV often rely on detecting PRRSV, culling or isolating sick pigs, disinfecting pig barns, vaccination, and monitoring for virus spread. Given the high economic impact of PRRSV on pig farms, there is a great need for rapid and reliable PRRSV detection assays. We compared the performance of 2 commercial reverse-transcription real-time PCR (RT-rtPCR) assays, the VetMAX PRRSV NA and EU reagents (ABI assay) and the PRRSV general RT-rtPCR kit (Anheal assay), for the molecular detection of PRRSV in sera collected from pigs in China. Between June and September 2015, sera were collected from 219 healthy and 104 suspected PRRSV-infected pigs on 4 farms in China. Employing blinding, the 2 assays were run by 2 laboratories (Guangzhou Animal Health Inspection Institute [GAHII] and Sun Yat-sen University [SYSU] laboratories) and compared. Although both assays detected PRRSV with 100% specificity at both laboratories, the sensitivity (95% vs. 78% at GAHII; 94% vs. 72% at SYSU Laboratory) and the reproducibility (kappa value 0.933 vs. 0.931) were slightly better for the ABI assay compared to the Anheal assay.

Epidemiological characteristics of human rabies in Henan province in China from 2005 to 2013.

BACKGROUND: Rabies is very common in People's Republic of China. Henan province, in the central portion of China, is one of the most densely populated provinces in the entire country. With the new rabies epidemic trend noted in northern and western China, it is necessary to investigate the characteristics of human rabies in this area and control the disease. METHODS: We chose patients in hospital isolation in 18 municipalities in Henan province as the investigation subjects. Data were collected through systematic reporting from these hospitals, whereas a questionnaire was applied to the relatives of patients. RESULTS: A total of 1022 rabies cases were reported. The incidence of human rabies in Henan has increased rapidly since 2005, having peaked in 2007, and maintained a high level in the remaining years. The cases were found mainly in rural areas in the south and east of the province. Rabies was often noted in summer and with the highest number in August. Most cases were noted in males and often in farmers. The patients aged between 40 and 60 years accounted for 36.8 % of all the cases. The wound treatment rate (12.2 %) and vaccination rate (2.6 %) of rabies cases after exposure were relatively low, while the rabies immunoglobulin utilization rate was only 2.8 %. CONCLUSIONS: Rabies epidemic cases at the county level overall were increasing in Henan province during the period of 2005-2013; the epidemic has spread quickly. The data in this study imply that the disease could be better managed by more integrated surveillance across human health and veterinary sectors, improved education and better government policies.

Evaluation of inapparent dengue infections during an outbreak in Southern China.

Few studies evaluating inapparent dengue virus (DENV) infections have been conducted in China. In 2013, a large outbreak of DENV occurred in the city of Zhongshan, located in Southern China, which provided an opportunity to assess the clinical spectrum of disease. During the outbreak, an investigation of 887 index case contacts was conducted to evaluate inapparent and symptomatic DENV infections. Post-outbreak, an additional 815 subjects from 4 towns with, and 350 subjects from 2 towns without reported autochthonous DENV transmission, as determined by clinical diagnosis, were evaluated for serological evidence of dengue IgG antibodies. Between July and November 2013, there were 19 imported and 809 autochthonous dengue cases reported in Zhongshan. Of 887 case contacts enrolled during the outbreak, 13 (1.5%) exhibited symptomatic DENV infection, while 28 (3.2%) were inapparent. The overall I:S ratio was 2.2:1 (95% CI: 1.1-4.2:1). Post-outbreak serological data showed that the proportion of DENV IgG antibody detection from the 4 towns with and the 2 towns without reported DENV transmission was 2.7% (95% CI: 1.6%-3.8%) and 0.6% (95% CI: 0-1.4%), respectively. The I:S ratio in the 3 towns where clinical dengue cases were predominately typed as DENV-1 was 11.0:1 (95% CI: 3.7-∞:1). The ratio in the town where DENV-3 was predominately typed was 1.0:1 (95% CI: 0.5-∞:1). In this cross-sectional study, data suggests a high I:S ratio during a documented outbreak in Zhongshan, Southern China. These results have important implications for dengue control, implying that inapparent cases might influence DENV transmission more than previously thought.

Epidemiological characteristics of human rabies in Henan province in China from 2005 to 2013

Background Rabies is very common in People's Republic of China. Henan province, in the central portion of China, is one of the most densely populated provinces in the entire country. With the new rabies epidemic trend noted in northern and western China, it is necessary to investigate the characteristics of human rabies in this area and control the disease.Methods We chose patients in hospital isolation in 18 municipalities in Henan province as the investigation subjects. Data were collected through systematic reporting from these hospitals, whereas a questionnaire was applied to the relatives of patients.Results A total of 1022 rabies cases were reported. The incidence of human rabies in Henan has increased rapidly since 2005, having peaked in 2007, and maintained a high level in the remaining years. The cases were found mainly in rural areas in the south and east of the province. Rabies was often noted in summer and with the highest number in August. Most cases were noted in males and often in farmers. The patients aged between 40 and 60 years accounted for 36.8 % of all the cases. The wound treatment rate (12.2 %) and vaccination rate (2.6 %) of rabies cases after exposure were relatively low, while the rabies immunoglobulin utilization rate was only 2.8 %.Conclusions Rabies epidemic cases at the county level overall were increasing in Henan province during the period of 2005-2013; the epidemic has spread quickly. The data in this study imply that the disease could be better managed by more integrated surveillance across human health and veterinary sectors, improved education and better government policies.(AU)

Epidemiological characteristics of human rabies in Henan province in China from 2005 to 2013

Background Rabies is very common in Peoples Republic of China. Henan province, in the central portion of China, is one of the most densely populated provinces in the entire country. With the new rabies epidemic trend noted in northern and western China, it is necessary to investigate the characteristics of human rabies in this area and control the disease.Methods We chose patients in hospital isolation in 18 municipalities in Henan province as the investigation subjects. Data were collected through systematic reporting from these hospitals, whereas a questionnaire was applied to the relatives of patients.Results A total of 1022 rabies cases were reported. The incidence of human rabies in Henan has increased rapidly since 2005, having peaked in 2007, and maintained a high level in the remaining years. The cases were found mainly in rural areas in the south and east of the province. Rabies was often noted in summer and with the highest number in August. Most cases were noted in males and often in farmers. The patients aged between 40 and 60 years accounted for 36.8 % of all the cases. The wound treatment rate (12.2 %) and vaccination rate (2.6 %) of rabies cases after exposure were relatively low, while the rabies immunoglobulin utilization rate was only 2.8 %.Conclusions Rabies epidemic cases at the county level overall were increasing in Henan province during the period of 20052013; the epidemic has spread quickly. The data in this study imply that the disease could be better managed by more integrated surveillance across human health and veterinary sectors, improved education and better government policies.

China's great wall, Israel's Bar Lev Line, and passive infectious disease surveillance.

Emerging infectious diseases are some of modern society's greatest threats. Like some great construction efforts designed to protect mankind, current public health measures against these emerging pathogens have not always been successful. This paper highlights the importance of embracing new interdisciplinary approaches towards emerging pathogen threats. One such approach, termed One Health, is quickly being embraced by professional organizations and public health institutions across the world as a way forward. This paper briefly discusses the above problems and preliminary steps taken by Chinese academic institutions to embrace the One Health approach.

Emergence of dengue virus 4 genotype II in Guangzhou, China, 2010: survey and molecular epidemiology of one community outbreak.

BACKGROUND: The re-emergence of dengue virus 4 (DENV-4) has become a public health concern in South America, Southeast Asia and South Asia. However, it has not been known to have caused a local outbreak in China for the past 20 years. The purpose of this study was to elucidate the epidemiology of one local community outbreak caused by DENV-4 in Guangzhou city, China, in 2010; and to determine the molecular characteristics of the genotype II virus involved. CASE PRESENTATIONS: During September and October of 2010, one imported case, a Guangzhou resident who travelled back from Thailand, resulted in 18 secondary autochthonous cases in Guangzhou City, with an incidence rate of 5.53 per 10,000 residents. In indigenous cases, 14 serum samples tested positive for IgM against DENV and 7 for IgG from a total of 15 submitted serum samples, accompanied by 5 DENV-4 isolates. With identical envelope gene nucleotide sequences, the two isolates (D10168-GZ from the imported index case and Guangzhou 10660 from the first isolate in the autochthonous cases) were grouped into DENV-4 genotype II after comparison to 32 previous DENV-4 isolates from GenBank that originated from different areas. CONCLUSIONS: Based on epidemiological and phylogenetic analyses, the outbreak, which was absent for 20 years after the DENV-4 genotype I outbreak in 1990, was confirmed as DENV-4 genotype II and initially traced to the imported index case, a Guangzhou resident who travelled back from Thailand.

Improvement of lipid profile and reduction of body weight by shan he jian fei granules in high fat diet-induced obese rats.

BACKGROUND: The goal was to study lipid profiles (TG, TC, LDL, HDL), effects on serum leptin, and fat tissue adiponectin, and resistin as well as body weight effects of Shan He Jian Fei Granules (SHJFG) in rats on a high fat diet. METHODS: Rats were randomly divided into five groups: normal control group fed with normal fat diet, rats on high fat diet receiving low dosage, middle dosage, high dosage of Shan He Jian Fei Granules (SHJFG) as well as a high fat diet group receiving placebo. Rats were treated for 8 weeks. Body weight and naso-anal length of each rat were recorded and Lee's index was calculated. Serum TG, TC, LDL, HDL and leptin concentrations were analyzed. The gene expressions of adiponectin and resistin in adipose tissues were tested by RT-PCR. RESULTS: Compared to the high-fat diet group, body weights, Lee's indexes, weight of fat tissues and serum TG, TC, LDL and leptin of SHJFG groups significantly decreased (p < 0.05), whereas mRNA expressions of adiponectin and resistin of SHJFG groups significantly increased (p < 0.05). CONCLUSIONS: SHJFG could significantly lower body weight and serum TG, TC, and LDL of obese rats. The effects of SHJFG in lowering leptin synthesis and raising mRNA expression of adiponectin and resistin in fat tissues may act as part of the mechanisms in lowering body weight of obese rats. Further studies are needed to demonstrate whether SHJFG may also reduce overall cardiovascular morbidity and mortality like other lipid lowering drugs.

Potential infections of H5N1 and H9N2 avian influenza do exist in Guangdong populations of China.

BACKGROUND: Southeast China is one of the sites of influenza origin. During 2003--2004, nine avian influenza outbreaks took place in Guangdong Province. But no human case was reported. To examine the status of potential human infection by human influenza (H1N1, H3N2) and avian influenza (H5N1, H7N7, H9N2) in the avian influenza epidemic area of Guangdong Province, China, we conducted a seroepidemiologic survey in the people of this area from April to June of 2004. METHODS: Three out of 9 H5N1 avian influenza affected poultry areas in Guangdong were randomly selected, and the population living within 3 kilometers of the affected poultries were chosen as the survey subjects. One thousand two hundred and fourteen people were selected from 3 villages at random. Human and avian influenza antibody titers were determined by hemagglutination-inhibition (HI) test and microneutralization test (MNT). RESULTS: The positive rate of antibody to H5N1 was 3.03% in the occupational exposure group and 2.34% in general citizens group; that of H9N2 was 9.52% in the occupational exposure group and 3.76% in the general citizens group. Moreover one case in the occupational exposure group was positive for H7N7. One year later, all previously positive cases had become negative except for one H5N1-positive case. CONCLUSION: The observations imply that H5N1 and H9N2 avian influenza silent infections exist in Guangdong populations.