Impact of Influenza on Outpatient Visits, Hospitalizations, and Deaths by Using a Time Series Poisson Generalized Additive Model.

BACKGROUND: The disease burden associated with influenza in developing tropical and subtropical countries is poorly understood owing to the lack of a comprehensive disease surveillance system and information-exchange mechanisms. The impact of influenza on outpatient visits, hospital admissions, and deaths has not been fully demonstrated to date in south China. METHODS: A time series Poisson generalized additive model was used to quantitatively assess influenza-like illness (ILI) and influenza disease burden by using influenza surveillance data in Zhuhai City from 2007 to 2009, combined with the outpatient, inpatient, and respiratory disease mortality data of the same period. RESULTS: The influenza activity in Zhuhai City demonstrated a typical subtropical seasonal pattern; however, each influenza virus subtype showed a specific transmission variation. The weekly ILI case number and virus isolation rate had a very close positive correlation (r = 0.774, P < 0.0001). The impact of ILI and influenza on weekly outpatient visits was statistically significant (P < 0.05). We determined that 10.7% of outpatient visits were associated with ILI and 1.88% were associated with influenza. ILI also had a significant influence on the hospitalization rates (P < 0.05), but mainly in populations <25 years of age. No statistically significant effect of influenza on hospital admissions was found (P > 0.05). The impact of ILI on chronic obstructive pulmonary disease (COPD) was most significant (P < 0.05), with 33.1% of COPD-related deaths being attributable to ILI. The impact of influenza on the mortality rate requires further evaluation. CONCLUSIONS: ILI is a feasible indicator of influenza activity. Both ILI and influenza have a large impact on outpatient visits. Although ILI affects the number of hospital admissions and deaths, we found no consistent influence of influenza, which requires further assessment.

The prevalence and endemic nature of dengue infections in Guangdong, South China: an epidemiological, serological, and etiological study from 2005-2011.

OBJECTIVES: Frequent outbreaks of dengue are considered to be associated with an increased risk for endemicity of the disease. The occurrence of a large number of indigenous dengue cases in consecutive years indicates the possibility of a changing dengue epidemic pattern in Guangdong, China. METHODS: To have a clear understanding of the current dengue epidemic, a retrospective study of epidemiological profile, serological response, and virological features of dengue infections from 2005-2011 was conducted. Case data were collected from the National Notifiable Infectious Diseases Reporting Network. Serum samples were collected and prepared for serological verification and etiological confirmation. Incidence, temporal and spatial distribution, and the clinical manifestation of dengue infections were analyzed. Pearson's Chi-Square test was used to compare incidences between different age groups. A seroprevalence survey was implemented in local healthy inhabitants to obtain the overall positive rate for the specific immunoglobulin (Ig) G antibody against dengue virus (DENV). RESULTS: The overall annual incidence rate was 1.87/100000. A significant difference was found in age-specific incidence (Pearson's Chi-Square value 498.008, P<0.001). Children under 5 years of age had the lowest incidence of 0.28/100000. The vast majority of cases presented with a mild manifestation typical to dengue fever. The overall seroprevalence of dengue IgG antibody in local populations was 2.43% (range 0.28%-5.42%). DENV-1 was the predominant serotype in circulation through the years, while all 4 serotypes were identified in indigenous patients from different outbreak localities since 2009. CONCLUSIONS: A gradual change in the epidemic pattern of dengue infection has been observed in recent years in Guangdong. With the endemic nature of dengue infections, the transition from a monotypic to a multitypic circulation of dengue virus in the last several years will have an important bearing on the prevention and control of dengue in the province and in the neighboring districts.

Epidemiologic and economic burden of influenza in the outpatient setting: a prospective study in a subtropical area of China.

OBJECTIVES: To understand the incidence of outpatient influenza cases in a subtropical area of China and the associated economic burden on patients' families. METHODS: A hospital-based prospective study was conducted in Zhuhai City during 2008-2009. All outpatient influenza-like illness (ILI) cases were identified in 28 sentinel hospitals. A representative sample of throat swabs from ILI cases were collected for virus isolation using Madin-Darby canine kidney cells. The incidence of outpatient influenza cases in Zhuhai was estimated on the basis of the number of influenza patients detected by the sentinel sites. A telephone survey on the direct costs associated with illness was conducted as a follow-up. RESULTS: The incidence of influenza was estimated to be 4.1 per 1,000 population in 2008 and 19.2 per 1,000 population in 2009. Children aged <5 years were the most-affected population, suffering from influenza at the highest rates (34.3 per 1,000 population in 2008 and 95.3 per 1,000 population in 2009). A high incidence of 29.2-40.9 per 1000 population was also seen in young people aged 5-24 years in 2009. ILI activity and influenza virus isolations adopted a consistent seasonal pattern, with a summer peak in July 2008 and the longest epidemic period lasting from July-December 2009. The medical costs per episode of influenza among urban patients were higher than those for rural patients. A total of $1.1 million in direct economic losses were estimated to be associated with outpatient influenza during 2008-2009 in Zhuhai community. CONCLUSIONS: Influenza attacks children aged <5 years in greater proportions than children in other age groups. Seasonal influenza 2008 and Pandemic influenza A (H1N1) 2009 had different epidemiological and etiological characteristics. Direct costs (mostly medical costs) impose an enormous burden on the patient family. Vaccination strategies for high-risk groups need to be further strengthened.

An enterovirus 71 epidemic in Guangdong Province of China, 2008: epidemiological, clinical, and virogenic manifestations.

Enterovirus 71 (EV71) is shown to be a major causative agent in outbreaks of hand, foot, and mouth disease (HFMD) reported in Guangdong (GD) Province of China in 2008. A total of 48,876 HFMD cases (131 severe and 21 fatal) were reported to the GD HFMD web-based surveillance system, which covers 871 clinics. The main causes of death included central nervous system damage, heart failure, and pulmonary edema. The incidence rate was 52 per 100,000, and the epidemic peak appeared in May and June. EV71 was found in 59% and coxsackievirus A16 in 26% of 936 laboratory-confirmed cases. Other viruses are likely to be responsible for the remaining 15% of cases. Of the 185 EV71 cases collected, 62% were mild, 27% were severe, and the remaining 11% were fatal. A total of 17 EV71 isolates were subjected to nucleotide sequencing of the entire VP1 gene. Phylogenetic analysis showed that the GD EV71 strains belonged to the C4 subgenotype and that EV71 circulates at a national rather than a regional level. A Comparison with the VP1 gene from a different clinical case showed that there was no obvious virulence determinant in this locus. Furthermore, this study found that most deaths occurred in rural areas, thereby indicating that delayed diagnosis and incorrect treatment may play an important role.

[Molecular epidemiological characteristics of norovirus gastroenteritis outbreaks in Guangdong from 2005 to 2008].

To study the molecular epidemiological characteristics of norovirus gastroenteritis outbreaks in Guangdong, we collected fecal and anal swabs specimens from 24 outbreaks of acute gastroenteritis from 2005 to 2008 to detect norovirus. Specimens were detected by RT-PCR and then sequenced. The descriptive data were also collected. According to our research, 19 of 24 outbreaks of gastroenteritis were positive for norovirus. The occurrence time was from October to next February mainly. The strains in 2005 belonged to G II-3 genotype and all outbreaks occurred in kindergarten and school. But from autumn of 2006, the outbreaks were all caused by G II-4/2006b variant and occurred in universities and community. The number of outbreaks in 2007 increased greatly and covered all over province. The nucleotide sequences of Guangdong strains in some sites showed high regional identity. Our results showed that with the shift of genotype from G II-3 to G II-4, occurrence of norovirus outbreaks increased greatly. The outbreaks of norovirus caused by G II-4/2006b variant spreaded widely and the involved population covered children and adult, indicating the strong invasiveness of this variant.

[Pathogens of high incidence of other infectious diarrhea in Guangdong Province, from November 2008 to January 2009].

From November 2008 to January 2009, a sharp increase of diarrhea in children in Guangdong province appeared, we randomly collected 53 stool specimens from out-patient children with dirrhea in 3 major hospitals (Guangzhou City Children's Hospital, Shenzhen Baoan District Maternal and Child Health Hospital, First Affiliated Hospital of Shantou University). Rotavirus and calicivirus were screened by ELISA and RT-PCR. We found 29 cases of rotavirus infection with diverse serotypes. Only four cases were identified as calicivirus infection. The result indicated that rotavirus was a major pathogen of this high incidence of diarrhea from November 2008 to January 2009 in Guangdong Province.

[An epidemiological study on the norovirus detected in the field environment after an outbreak of norovirus gastroenteritis].

OBJECTIVE: To study the status of norovirus in environment of the patient's residence and water samples after a norovirus gastroenteritis outbreak, to provide evidences for the development of strategies for prevention and control of the disease. METHODS: After a norovirus gastroenteritis outbreak, anus swabs from the patient, swabs from the household environment and the water samples were collected to detect the norovirus by RT-PCR methods. Sequencing analysis was conducted on those positive specimens. RESULTS: Three specimens of the anus swabs from 9 patients and 2 samples of the 46 house environment swabs were positive to the virus. The latter were from the surface of water-closets of two families that the illness were asymptomatic. Among 5 water samples, only one was positive, which was the rivulet water that the feces of the villagers evacuated directly. RESULTS: showed that the sequences of the virus detected from the anus swabs of the patients, the swabs from the household environment and the samples of the rivulet water belonged to the same species. CONCLUSION: It is necessary to strengthen activities as supervision and disinfection to the feces of the patients, especially on monitoring the feces that might have contaminated the water during the norovirus gastroenteritis outbreak.

[Investigation of a norovirus outbreak through contaminated centralized water supply system].

OBJECTIVE: To investigate the etiology and source of an infectious diarrhea outbreak and control the epidemic. METHODS: Through the retrospective cohort study, we had surveyed all the residents who complained symptoms of diarrhea or vomiting since Nov. 20th,2007 from the five villages in the north of town Y, and collected hygiene information on the water supply system of the five villages, the environment information of three villages and hygiene information of some case-indexed families, and tested the etiological biomarker, including nucleoside acid of norovirus through Real-time PCR and nested PCR technologies. RESULTS: From Nov. 24th to Dec. 3th in 2007, 435 diarrhea or vomiting cases were found in the north of Y town, where tap water A was supplied for daily use. The attack rate was 12.93%. The diarrhea cases were distributed among all country groups who has used tap water A and the attack rate was ranged from 5.21% (20/384) to 21.23% (100/471). Drinking the tap water A was significantly associated with an increased risk of infection (RR = 9.246, 95% CI: 6.25 -13.68). About 85.9% (262/ 305) of the cases were from Nov. 25th to 27th. An investigation of a country of S2 group showed that the incidence of different age groups was distributed as the following: 0 - year-old 20.0% (3/15); 10 - year-old 17.3% (9/52); 20 - year-old 15.2% (16/105); older than 60 year-old 23.3% (7/30). No statistical significance was identified between age and infection(chi2 = 1.15, P >0.05). Most of the patients were not serious and well prognostic, and no hospitalized or dead cases were reported. On site investigation and daily water quality monitoring showed that disinfection procedures were not strictly followed. The monitoring data also indicated the bacteriology index of tap water A was disqualified. The test of Salmonella, Shigella and Staphylococcus aureus were negative in two vomit and one stool samples from patients. Three specimens by Real-time PCR, and six by nested PCR were positive for norovirus among the three feces and three anal swabs samples. With the drinking water sterilization and health education, the epidemic had been controlled rapidly and effectively. CONCLUSION: The epidemic was a diarrhea outbreak that might be caused by norovirus through drinking the contaminated tap water A.

[Severe acute respiratory syndrome in Guangdong Province of China: epidemiology and control measures].

OBJECTIVE: To explore epidemiological features and risk factors of severe acute respiratory syndrome (SARS) in Guangdong Province of China, so as to work out effective strategies for its better control. METHODS: A total of 1 511 clinically confirmed SARS cases in Guangdong Province of China from November 16, 2002 to Jun 15, 2003 were retrospectively analyzed. RESULTS: The first SARS case was identified in Foshan municipality on November 16, 2002, followed by 1 511 clinically confirmed cases (including 58 deaths) up to May 15, 2003. Of all cases, health care workers and community family cluster cases accounted for 19.38% and 12.04%. 65.86% SARS patients aged 20 - 49 years, and increased incidence was positively related to their ages. 95.97% cases lived in the following five cities around Pearl Delta Area: Foshan, Guangzhou, Shenzhen, Zhongshan, and Jiangmen. Eleven early reported cases in the communities took animal-related positions. Face-to-face contacts with infected droplets were the main transmission route. An epidemic peak occurred during January 28 to February 26, and those cases accounted for 50.69% of total. Incidence, mortality, and case fatality of SARS were 1.77/100,000, 0.07/100,000, and 3.84% respectively. The mean incubation period was 4.5 days. CONCLUSION: The most effective way to control SARS is to break the chain of transmission from infected to healthy persons-early identification, prompt and effective isolation, and vigorous close contact tracing. Hospital infections among health care workers is critical. Several observations support the hypothesis of an animal origin for the disease.

[An epidemiological study on the index cases of severe acute respiratory syndrome occurred in different cities among Guangdong province].

OBJECTIVE: To analyze the epidemiological features of the index cases of severe acute respiratory syndrome (SARS) occurred in different cities in Guangdong province and to trace for the source of infection. METHODS: Standardized individual case inventory was adopted to conduct investigation on index cases and on persons who had close contact with index cases in Guangdong province. Data on the epidemiological characteristics, secondary cases and the links among index cases were analyzed. RESULTS: Between November 16, 2002 and April 16, 2003, there had been 13 index cases of SARS including 3 cadres, 3 farmers, 2 retirees, 2 workers and 1 shop attendant, reported from 13 cities in Guangdong province. Between November 2002 and January 2003, there had been 7 cities reported to have identified index cases of SARS with 6 of them being infected in their own cities and 1 imported from Guangzhou city. All of the cases had no close contacts to similar patients but 6 of them later caused 2nd or even 3rd generation cases of SARS. Most cases hit young people (7/13) with a sex ratio of 1:0.6. The fatality rate of index cases was high (4/13). CONCLUSION: No evidence showed that there was direct transmission among the index cases. Data regarding the geographical origin of those index cases led to the assumption that the infection had started in six cities of Pearl river delta region and the Hong Kong Special Administrative Region.

[Epidemiological study on severe acute respiratory syndrome in Guangdong province].

OBJECTIVES: To understand the epidemiological characteristics of severe acute respiratory syndrome (SARS) outbreaks in some areas of Guangdong province and to provide scientific basis for prevention and control measures against it. METHODS: Standardized questionnaire was used on individual cases. Data on the epidemiological characteristics as time, place, persons and aggregation status of SARS cases, development of the epidemics, were analyzed with software EPI 6.0. RESULTS: The incidence of SARS in Guangdong province was 1.72/100,000 with case fatality rate as 3.64%. Most cases of SARS occurred between the last ten days of January and the first ten days of February with the peak (61.88% of the patients) occurred in the first ten days of February. As to the distribution of place, Pearl river delta region-economically developed with great number of mobile population-was heavily affected areas (account for 96.66% of the total patients). The majority of patients were young adults and medical staff seemed to be the most affected subgroup (account for 24.9% of the patients in total). Family and hospital aggregation of patients comprised the another two important characteristics of SARS (account for 37.1% of the total patients). CONCLUSION: Current knowledge on SARS suggested that it was an air-borne infectious disease with human beings served as the source of infection. The incubation period of the disease was from 1 to 12 days with a median of 4 days. Respiratory secretions and close contact contributed to person-to-person transmission. Most cases were distributed in Pearl river delta region, an area famous for its economic development and heavy flow of mobile population.