Studies on the environment structure of natural nidi and epidemic areas of hemorrhagic fever with renal syndrome in China.

The environment structure of natural nidi and epidemic areas of hemorrhagic fever with renal syndrome (HFRS) possesses characteristics of topography, hydrology, climate, soil, vegetation, and animals. The natural nidi and epidemic areas of HFRS are distributed mainly in plain and hilly regions under 500 meters above the sea level; in plentiful-water zones and transitional zones; in temperate zone and subtropical zone of the eastern monsoon region; in the abundant-aluminum soil region and the sial soil region; in the eastern China damp forest region (agricultural districts and northeast forest districts); in the eastern Asia dampness-preferring animal geographic region. Apodemus agrarius and Rattus norvegicus are the thriving animal population, predominant species or common species as well as the main reservoir hosts and sources of infection in the natural nidi and epidemic areas of HFRS.

Epidemiologic surveillance on the hemorrhagic fever with renal syndrome in China.

This article summarizes the contents and results of extensive surveillance on hemorrhagic fever with renal syndrome (HFRS) in China. Data from surveillance on human HFRS, including morbidity and case fatality rate, trend of epidemics, periodicity of epidemics, factors related to epidemics, types of epidemic areas, environment structure of natural nidi, geographic distribution, seasonal distribution, age distribution, sex distribution and occupation distribution, as well as surveillance on animal infection with HFRS virus were collected and analysed.

Dengue in China: a clinical review.

Three etiologically proven outbreaks of dengue fever and one etiologically confirmed epidemic of dengue haemorrhagic fever have occurred in south China since 1978. The first of these, an epidemic of dengue due to virus type 4 took place in Shiwan town, Foshan city, Guangdong Province, in 1978; the epidemic began in May and ended in November. The clinical manifestations of 583 hospitalized patients were observed from August to October. The majority (81.3%) of patients were aged 21-50 years (male:female = 1.2:1). The course of illness was about 1 week in most cases; three patients (0.5%) died. A local outbreak of dengue due to virus type 1 occurred in Shiqi town, Zhongshan County, Guangdong Province, from September to November 1979. The majority of patients were older children and adolescents. There was no marked difference between males and females in terms of the course of the illness, and there were no complications or deaths. A large epidemic of dengue due to virus type 3 occurred on Hainan Island in 1980. The clinical manifestations of 510 hospitalized patients (mostly adolescents and adults) were observed from April to September. Some patients developed rare complications, such as loss of hair, acute intravascular haemolysis, and multiple peripheral paralysis; there were four deaths (0.78%). The first known epidemic of dengue haemorrhagic fever in China occurred among 10-29-year-olds on Hainan Island in 1985 and 1986. There were no essential differences between males and females. Some cases had rare complications such as acute intravascular haemolysis, while others had diffuse intravascular coagulation and altered mental status; 10 patients (6.5%) died.

Isolation of Getah virus from mosquitos collected on Hainan Island, China, and results of a serosurvey.

An isolate of Getah virus was obtained from Culex mosquitos collected in Mao'an Village, Baoting County, Hainan Province, China, in 1964. The virus (strain M-1) replicated in laboratory-bred Aedes aegypti and Cx. fatigans (= quinquefasciatus), and was transmitted by laboratory-bred Ae. albopictus to healthy newborn albino mice. Skeletal muscles of newborn albino mice experimentally infected with the virus showed degeneration, atrophy, necrosis, and inflammatory changes of muscle fibers. Antibody prevalence in humans and animals ranged from 10.3% by neutralization tests of samples from healthy people in 1979 to 26.4% by CF tests of samples from people with febrile illnesses in 1982. The high prevalence of antibody in pigs, horses, and goats (17.6% to 37.5%) indicated that infection with Getah or a closely related virus is relatively common in domestic animals.

The first epidemic of dengue hemorrhagic fever in the People's Republic of China.

The first epidemic of dengue in China associated with significant severe and fatal hemorrhagic disease which met the World Health Organization case definition occurred on Hainan Island in 1985-1986. The epidemic began in Zhan County in September 1985, spread throughout the coastal areas, and ultimately involved 13 counties and cities of the island in 1986. The mosquito vector was Aedes aegypti. The morbidity associated with dengue infection on Hainan Island was 1,913 per 100,000 residents, with a case fatality rate of 0.25%. Severe disease was more prevalent in the 10-29-year-old age group. Principal clinical features in laboratory-confirmed cases were fever, osteoarthralgia, hemorrhage and/or shock, and thrombocytopenia. Complications such as acute intravascular hemolysis, diffuse intravascular coagulation, hemoconcentration, pleural effusion, altered mentality, and pneumonia were also observed. One hundred twenty-five isolates of dengue 2 virus were recovered from acute-phase serum samples from 278 patients, and 5 strains of this same virus serotype were isolated from 5 pools of adult Ae. aegypti.

Detection and preliminary studies of small double capsid virus.

This article reports the detection of small double capsid virus and results of preliminary studies on its morphology, serology and relationship to gastroenteritis. A kind of small virus particles with morphological characteristics was found in fecal samples of 3 of 23 infants with autumn gastroenteritis. The average diameter of this virus particles is 34.1 +/- 1.1 nm, possessing core, double capsids and spoke-like capsomers. It can be differentiated from other viruses in morphology. Correlated antigenicity exists among 3 strains of the virus but not among other studied viruses and this virus. The titer of the antibody to small double capsid virus in convalescent phase-sera of 2 patients was more than 4-fold as high as that in control sera. This virus was absent in fecal samples of recovered patients as well as in those of normal infants. These show that small "double layer like" capsid virus might be one of the etiological agents of acute gastroenteritis.

Serotyping and subgrouping of some rotavirus strains in China.

This article reports for the first time in China the results of serotyping and subgrouping of some rotavirus strains obtained from faecal fluids of cases with infant diarrhoea. Infant diarrhoea rotavirus serotype 1 (Wa strain)-specific and serotype 2 (KUN strain)-specific hyperimmune sera, and infant diarrhoea rotavirus serotype 3-specific, rotavirus subgroup I-specific and subgroup II-specific monoclonal antibodies were used in serotyping and subgrouping by means of enzyme-linked immunosorbent assay of 14 rotavirus strains which had been identified by electron microscopy. Results showed that three out of four Beijing strains in 1982 belonged to serotype 2 and subgroup I rotavirus, one belonged to serotype 3 and subgroup II rotavirus; one out of nine Beijing strains in 1984 belonged to serotype 1 and subgroup II rotavirus, seven belonged to serotype 2 and subgroup I rotavirus, one belonged to serotype 3 and subgroup II rotavirus; and one Kunming strain in 1984 belonged to serotype 3 and subgroup II rotavirus.

Epidemiological studies on hemorrhagic fever with renal syndrome in China.

Hemorrhagic fever with renal syndrome (HFRS) has been reported from greater than 20 provinces in China. The number of reported cases has increased markedly in recent years and surpassed 80,000 human cases in 1983. All of the cases reported before 1981 were from rural areas and were attributed to Apodemus rats. In 1981, outbreaks of cases associated with house rats were first reported. Cases associated with Apodemus agrarius were more severe than those associated with the house rat Rattus norvegicus. The rate of inapparent infection in the rural population of areas endemic for Apodemus-associated disease was lower than that of Rattus-associated urban disease. After the onset of the disease, IgG antibody levels increase rapidly, peak after one week, and persist for as long as 25 years. Lung tissues from 16 species of rodent, from two species of sorex, and from cats and weasels in the epidemic areas have been found to carry antigen. A. agrarius, Apodemus peninsulae, and R. norvegicus serve as the main reservoirs of HFRS in rural areas, forest areas, and urban areas, respectively.

Etiologic and serologic investigations of the 1980 epidemic of dengue fever on Hainan Island, China.

Virologic and seroepidemiologic studies were carried out during an epidemic of dengue fever on Hainan Island in 1980. Dengue 3 virus was isolated from 46 of 77 acute phase sera and from 1 of 10 pools of adult Aedes aegypti. Dengue 1 virus virus was isolated from a single acute phase serum. Seroepidemiologic investigations showed that 74% of healthy individuals in the epidemic area had antibody to dengue virus compared to 54% in an area where epidemic dengue had occurred in 1978, and less than or equal to 8% in nonepidemic areas. There were no significant differences in antibody prevalence for different sex and age groups.

Antibody against adult diarrhoea rotavirus among healthy adult population in China.

This paper deals with a method of using unknown serum as the first antibody to coat wells of the microtiter plate directly in application of the sandwich ELISA method with double antibodies for the assay of the antibody against adult diarrhoea rotavirus. This method was used for assay of the antibody against adult rotavirus in 1,380 sera of healthy adults obtained from some provinces and cities of China, of which 141 showed a positive result with a total positive rate of 10.2%. The infection rate varied in different regions. In order to confirm the accuracy of these results a blocking test was carried out on 25 positive specimens, and the results revealed that the P/N ratios after blocking were all lower than those before blocking. Seventeen of these 25 positive serum specimens were obtained from rural areas of Qian'an County, Hebei Province where epidemic adult diarrhoea had occurred two years ago. The antibody against adult diarrhoea rotavirus was not detected in 50 adult sera from Xizang Autonomous Region. Only one out of 50 adult sera from Hainan Island was positive for the antibody.