Investigation of an outbreak of adenovirus type 3 infection in a boys' boarding school

An outbreak of pharyngoconjunctival fever caused by adenovirus type 3 was studied in a boarding school for 800 boys aged 11-18 years. A total of 96 clinical cases were confirmed by laboratory tests. Clinical infection rates were higher in the younger boys but total infection rate did not vary with age. Previous infection provided 88% protection against reinfection. The techniques of virus isolation, complement fixation and neutralization were compared in the diagnosis of cases. Virus isolation diagnosed 86% of confirmed cases. Where acute sera (collected at onset) and convalescent sera (collected within one month) were available complement fixation and neutralization tests each diagnosed 96% of cases.     

Antibodies in horses, mules and donkeys following monovalent vaccination against African horse sickness

A total of 256 sera collected from three species of domesticated equidae in four different Spanish provinces were examined 1-4 months after the administration of attenuated monovalent African horse sickness virus (AHSV) serotype 4 vaccine. Approximately 10% of the sera were negative by ELISA, virus neutralization, agar gel immuno-diffusion and complement fixation tests. Similar negative reactions were recorded with sera from two ponies after experimental primary vaccination. The rapid rise in antibodies in sera from these two ponies, after a second dose of vaccine, suggested they would probably have been immune to challenge. It is therefore suggested that the apparent absence of antibodies against AHSV in some animals after primary vaccination may not necessarily indicate a total lack of protection.     

Comparison of agglutination, complement fixation and immunofluorescence tests in Campylobacter jejuni infections.

Good antibody responses usually follow infection with Campylobacter jejuni. A comparison of agglutination, complement fixation and immunofluorescence tests was done on 55 sera from 40 sporadic patients with diarrhoeal disease and positive cultures for C. jejuni. Results showed 82% positive with immunofluorescence, 62% by complement fixation but only 38% by agglutination, using two reference strains COP and MEL as antigens. Overall 90% of the 40 patients were positive by one or more serological tests. Paired sera from 15 patients showed a fourfold or greater rise in only five, confirming previous observations that antibody formation occurs early in the course of infection. Results also suggest that different test systems may be detecting antibodies of different specificities. Results confirm the value of serological tests, but further information on serotypes is required for selection of suitable reference strains.     

一起诺如病毒感染引起的职业学校暴发疫情分析

目的 分析南京市一起职业学校诺如病毒感染暴发疫情特征,探讨调查处置经验。方法 通过现场流行病学方法搜集信息,应用描述性流行病学方法分析疫情流行病学特征,采集疑似病例及无症状人员肛拭子、环境、食物标本,进行病原学检测。结果 搜索到疑似病例96例,其中确定临床诊断病例90例,确诊病例6例,全校患病率为9.50%(96/1 010)。男生患病率为18.60%,高于女生的9.05%(χ2=7.947,P＜0.01)。寄宿生患病率为11.10%,高于走读生的4.79%(χ2=6.061,P＜0.05)。疑似病例诺如病毒核酸检测阳性率22.22%(6/27),无症状人员阳性率12.20%(5/41),二者差异无统计学意义(χ2=1.207,P=0.324)。4名食堂无症状感染员工于首次检测诺如病毒GⅡ型阳性1周后(4月15日)再次采集肛拭子进行核酸检测,仍有2人为GⅡ型诺如病毒阳性,副溶血性弧菌、沙门氏菌、金黄色葡萄球菌和志贺氏菌4种致病均未检出。结论 该起事件可能是由GⅡ型诺如病毒引起的校园急性胃肠炎暴发疫情,应加强无症状感染者携带诺如病毒的监测。     

Influenza B in households: virus shedding without symptoms or antibody response

In the fall of 1983, 53 households were enrolled in a double-blind trial of alpha 2-interferon as an intranasal spray to prevent common colds. During the winter/spring of 1984, 26 households were infected with influenza type B, as shown by isolation of the virus (19 households) and/or significant antibody titer rises (seven households). Interferon did not prevent influenza B infection or modify resulting illness. Of 37 persons shedding virus, 12 were asymptomatic. All were older than age 12 years, and 10 did not respond with antibody by any of the five test methods employed (complement fixation, hemagglutination inhibition, enzyme-linked immunosorbent assay (ELISA), neutralization, and Western blot). In contrast, of 13 symptomatic persons shedding virus from whom sera were available, 11 had significant antibody titer rises. Infection rates were highest among teenagers, but also surprisingly high among the 11 persons observed who were aged 50 years or older, four of whom were infected. The case-to-case interval in household transmission varied between one and nine days. Longer intervals of one, two, and four months between infections among family members were also observed, suggesting repeated introductions. Neither virus isolation alone nor serologic tests was sufficient to estimate infection rates.     

Sporadic cases of haemorrhage and-or shock during dengue epidemics

Dengue haemorrhagic fever (DHF) usually occurs in epidemic form. Whilst investigating two epidemics of classical dengue, 8 sporadic cases with haemorrhage and/or shock were encountered. Although dengue virus was not isolated from them, results of examination of paired sera of 2 of them and acute sera of others by haemagglutination-inhibition and complement fixation tests against group A and group B arbovirus antigens suggest that the illness was the result of dengue virus infection. The importance of bearing in mind the possibility of sporadic cases of DHF is stressed.     

Single-radial-haemolysis test for diagnosing flavivirus infections, particularly Japanese encephalitis

Use of the single-radial-haemolysis (SRH) technique for the diagnosis of flavivirus infections is described. A large number of paired and single convalescent serum samples collected from cases of encephalitis during two major outbreaks in Kolar district of Karnataka State in India during 1977 and 1979 were tested by this technique. The results were compared with those obtained in the haemagglutination inhibition (HI) test in all cases, and the complement fixation (CF) and neutralization tests in some cases. Japanese encephalitis virus was shown by the SRH test to be the major etiologic agent responsible for both epidemics. This was corroborated by the HI, CF and neutralization test results. The single-radial-haemolysis test was found to be simpler and more specific and sensitive than the haemagglutination inhibition test.     

An epidemic of Rift Valley fever in Egypt. 1. Diagnosis of Rift Valley fever in man.

Rift Valley fever (RVF) virus was isolated from 53 of 56 sera collected from patients with a clinical picture of dengue-like illness during the peak of the epidemic of RVF in Egypt in the autumn of 1977. RVF virus was also isolated from the throat washings of two patients and the faeces of four, all of whom were positive for virus isolation from the serum. All the isolates were identified by the complement fixation (CF) test. Serological diagnosis of RVF, using paired sera from 16 patients, was made by both the haemagglutination-inhibition (HI) and CF tests. HI antibodies were demonstrated in all the acute sera, whereas CF antibodies, which seem to appear later, were detected in only seven acute and twelve convalescent sera. A longer period than the 12 days in this study must be allowed to elapse between the taking of the paired sera for a definite serological diagnosis to be obtained, especially when CF antibodies are taken into account.     

The status of dengue fever virus in South Africa--serological studies and diagnosis of a case of dengue fever

To assess the possibility of a dengue epidemic occurring in South Africa 3 groups of survey sera and 2 groups of patients' sera, from a dengue high risk area of South Africa, were tested for antibodies to several flaviviruses. 3.8% (75/1951) of the survey sera and 9.2% (26/282) of the patients' sera had haemagglutination inhibition antibodies to one or more of the flaviviruses tested. One of 1951 survey sera had a spectrum of complement fixation antibody consistent with a primary dengue infection, and 5 of 282 patients' sera also had complement fixation antibodies to flavivirus antigens. These 5 positive patients had recently travelled to India but in only one was there an antibody spectrum unequivocably consistent with a primary dengue infection. Dengue virus type 1 was successfully isolated from this patient's acute serum. The susceptibility of the population to dengue virus infection, the presence of the main vector of dengue virus and the occurrence of imported cases of dengue fever emphasize the need for continuous vigilance.     

The diagnostic efficiency of some serological tests for bovine brucellosis.

Results obtained from 1887 sera using three serological tests for bovine brucellosis were compared with a serological classification of sera described as the 'probable infection status'. Sera showing apparent false positive and apparent false negative reactions were identified, and were subjected to supplementary testing as appropriate. The serum agglutination test (SAT) gave 35% apparent false negative reactions and 5% apparent false positives. The complement fixation test (CFT) gave 12% apparent false negative reactions using warm fixation (CFTW) and at least 5% using cold fixation (CFTC). The routine diagnostic system used in Victoria, in which the CFTW is supplemented by the CFTC and the SAT, gave 9% apparent false negative reactions and 2% apparent false positive reactions. The radioimmunoassay gave 1% or 6% apparent false negative reactions, depending on the minimum diagnostic value used. Atypical reactions in the CFT sometimes caused difficulties in diagnosis.     

Nitrocellulose dot-ELISA for serodiagnosis of schistosomiasis

The diagnostic value of the nitrocellulose (NC)-ELISA technique originally described for the detection of viral and bacterial antigens was studied for the detection of antibodies in patients with parasitologically confirmed schistosomiasis, using only about 100 ng total protein content per NC disc of Schistosoma mansoni soluble egg antigen supplied by WHO. The results showed excellent sensitivity: 100% (38/38) for S. mansoni cases and 93.6% (44/47) for S. haematobium. The specificity tested on 50 sera of persons from non-endemic areas was also 100%. 34 sera of patients suffering from other parasitoses were also included. 3 sera of 10 from filariasis cases reacted positively by NC-ELISA, but they were also positive by indirect immunofluorescence, indicating a possible undetected Schistosoma infection. One positive reaction among sera from 4 toxocariasis cases was not confirmed by further tests. We conclude that the NC-ELISA can be a useful technique, especially in developing countries where tests with low cost equipment are needed. Large-scale screening studies should be done to evaluate its usefulness under field conditions.     

Different diagnostic methods for detection of influenza epidemics

Linking continuous community-based morbidity recording of influenza-like illness (ILI) with virological sampling has consistently proved its value as one of the earliest indicators of circulating influenza activity. The clinical morbidity recording in the Portuguese national surveillance network, during a 7-year period, and the contribution of different diagnostic techniques, including virus isolation, multiplex RT-PCR, immunocapture enzyme linked immunoassay (EIA) and complement fixation tests (CFTs) for the detection of influenza in such a community-based setting is described and evaluated in this study. There was good correlation between the increase of morbidity, total samples taken and the detection of influenza virus by all the methods although this was less evident for virus isolation and EIA than for RT-PCR or serology. From a total of 1685 throat swabs collected from cases of ILI, 43.6% were RT-PCR positive, 17.5% were positive by capture EIA and in 5% virus isolates were made. The detection of influenza by RT-PCR occurred earlier than by any other method and showed the best correlation with epidemic patterns of morbidity registration. We conclude that in surveillance systems where virus culture is sub-optimal, RT-PCR provides a rapid, sensitive, specific method for detecting influenza viruses from community-based sampling.     

Comparison of techniques for demonstrating antibodies to Rift Valley fever virus

Nine serological techniques were compared by monitoring the response to infection with Rift Valley fever (RVF) virus in three sheep. Antibodies were monitored daily for the first 14 days after infection, then weekly and later fortnightly up to week 24. The earliest antibody response was detected in one sheep on day 3 by a plaque reduction neutralization test, and by day 6 antibodies were demonstrable in all three sheep by haemagglutination-inhibition, reversed passive haemagglutination-inhibition, immunodiffusion, indirect immunofluorescence (IF), enzyme-linked immunosorbent assay and neutralization of cytopathic effect in cell cultures. Antibodies were demonstrable by complement fixation on day 8 at the earliest. IF and the two neutralization techniques produced the highest titres, but all tests could be used satisfactorily for the serological diagnosis of RVF. Inactivated antigen could be used for all except the neutralization tests. A radioimmunoassay technique using 125I-labelled staphylococcal protein A detected antibodies on day 8 at the earliest and produced lower mean titres than some of the other techniques. This was probably because sheep immunoglobulins bind protein A poorly.     

Comparison of techniques for demonstrating antibodies to Rift Valley fever virus.

Nine serological techniques were compared by monitoring the response to infection with Rift Valley fever (RVF) virus in three sheep. Antibodies were monitored daily for the first 14 days after infection, then weekly and later fortnightly up to week 24. The earliest antibody response was detected in one sheep on day 3 by a plaque reduction neutralization test, and by day 6 antibodies were demonstrable in all three sheep by haemagglutination-inhibition, reversed passive haemagglutination-inhibition, immunodiffusion, indirect immunofluorescence (IF), enzyme-linked immunosorbent assay and neutralization of cytopathic effect in cell cultures. Antibodies were demonstrable by complement fixation on day 8 at the earliest. IF and the two neutralization techniques produced the highest titres, but all tests could be used satisfactorily for the serological diagnosis of RVF. Inactivated antigen could be used for all except the neutralization tests. A radioimmunoassay technique using 125I-labelled staphylococcal protein A detected antibodies on day 8 at the earliest and produced lower mean titres than some of the other techniques. This was probably because sheep immunoglobulins bind protein A poorly.     

新型冠状病毒肺炎聚集性疫情中无症状感染者与确诊患者的流行差异

 目的 探讨无症状新型冠状病毒感染者(无症状感染者)流行特征。方法 通过中国疾病预防控制系统,收集、汇总河南省含有无症状感染者的聚集性疫情,描述其流行特征,分析与新型冠状病毒肺炎确诊病例流行特征的差异。结果 共报告聚集性疫情257起,其中41起有无症状感染者,包含84例无症状感染者,占全省无症状感染者的74.34％(84/113)。无症状感染者聚集性疫情分布在11个地市,涉及新型冠状病毒感染者208例,平均每起波及新型冠状病毒感染者5.07(2~19)例,16起(39.02%)新型冠状病毒感染者≥5例。无症状感染者的发现以聚集性疫情调查为主,确诊时间晚于新型冠状病毒肺炎确诊病例。河南省各地市无症状感染者占新型冠状病毒感染者的比率,以商丘市最高,为26.02%。无症状感染者与新型冠状病毒肺炎确诊病例比较,性别分布流行病学史方面,差异均无统计学意义(均P>0.05);年龄及职业的分布构成比较,差异均有统计学意义(均P<0.05),无症状感染者≤40岁者占58.33%,学生、儿童占28.57%,确认者分别占21.77%、4.03%。结论 无症状感染者在年龄和职业分布上与新型冠状病毒肺炎确诊病例存在差异。聚集性疫情调查是发现无症状感染者的主要途径,对密切接触者进行有效的隔离管理是正确有效的防控措施。     

对1974例乙型肝炎表面抗原定量检测阳性标本进行确认实验的研究

目的:探讨乙型肝炎表面抗原定量检测阳性标本进行确认实验的研究。方法:收集化学发光微粒子免疫分析法(CMIA)检测HBsAg阳性标本1974例,应用酶联免疫吸附试验(ELISA)等方法复检,对ELISA法末检出的标本进行CMIA法中和确证实验。结果:1974例标本使用ELISA法检测HBsAg有漏检现象的发生,漏检率为9.1%。漏检标本经CMIA法中和确证实验阳性率为96.67%,有6例无法确认。结论:定性方法在HBsAg检测上与发光等定量方法相比存在明显不足。对低浓度HBsAg阳性者应通过中和试验等予以确认。     

Diagnosis of Mycoplasma pneumoniae infection by specific IgM antibodies using a new capture-enzyme-immunoassay

A total of 1226 sera from 1055 patients with respiratory tract infections were tested. IgM antibodies were detected by an antibody-capture enzyme-immunoassay (Mp TEST, Diatech Diagnostica Ltd, Israel). Acute infection with IgM antibodies to Mycoplasma pneumoniae was detected in 211 patients.Presence of IgM was closely associated to some or all pneumonia-related symptoms. Eighty-one of IgM-positive patients treated with tetracycline or erythromycin responded positively. Of the 211 patients, 63 (30%) had low levels and 23 (11%) had moderate levels of IgM antibodies already in the first serum sample. In these 86 patients (41%) the complement fixation (CF) test was negative or very low positive. Thus in these cases, the CF test would have missed the early diagnosis in the first serum samples.     

两种酶结合物诊断布鲁氏菌病的研究

以两种酶结合物(SPA-HRPO及兔抗人IgG-HRPO)做酶联免疫吸附测定(ELISA),对临床诊断为布鲁氏菌病人的血清51份进行了检査。结果除一例阴性外,其余50份均呈阳性反应。阳性效价为1:20~1:5120。用两种结合物检查结果基本一致,阳性率为98%。同时以凝集反应、2-ME试管凝集反应、补体结合反应虎红平板抗原凝集试验方法作了对比检查,阳性率分别为41%、35%、39%、31%。为了解ELISA法测定结果的特异性,使用混合布氏菌抗原吸收了被检血清,原来的阳性血清在吸收之后转成阴性。由于实验结果说明ELISA法作为布病诊断方法之一是可用的。     

Further evaluation of one-point microcapsule agglutination test for diagnosis of leptospirosis

A total of 100 serum samples including 22 acute phase sera and 39 paired sera collected from clinically diagnosed cases of leptospirosis in Ming-shan County, Sichuan Province, China were examined by the one-point microcapsule agglutination test (MCAT), which was developed in Japan, and by conventional microscopic agglutination tests (MAT). The one-point MCAT is more reactive to IgM antibody than MAT and is superior in detecting antibodies in the early stages of the disease.