Human Infection Rates Research Articles

Lymphatic filariasis in Papua New Guinea: interdisciplinary research on a national health problem.

Bancroftian filariasis is a major public health problem in Papua New Guinea, where the level of transmission by the mosquito vector, human infection rates and clinical morbidity are among the highest in the world. Coordinated research efforts within the country, involving the disciplines of epidemiology, vector biology, immunology and genetics, have led to new insights into the ecology and pathogenesis of human lymphatic filariasis. Recent work using this knowledge base should be helpful in assessing local and global strategies aimed at eliminating Wuchereria bancrofti and in guiding research that will facilitate achievement of this goal.

Factors influencing the shedding of verocytotoxin-producing Escherichia coli O157 by beef suckler cows.

A study was designed to investigate management factors that might influence the shedding of verocytotoxin-producing Escherichia coli (VTEC) O157 by beef cows in Scotland, where there is a particularly high rate of human infection. Thirty-two herds were visited at least monthly over approximately 1 year for collection of fresh faecal pat samples and information on management factors. The faecal pat samples were tested for VTEC O157 by established culture and immunomagnetic separation methods. Questionnaires were completed at the monthly visits to record management factors. Data were analysed using both univariate and multi-factor (GLMM) analysis. Changes in the number of cows in a group, dogs, wild geese, housing, and the feeding of draff (distillers' grains) were statistically significant as risk factors. The event of calving appeared to reduce the likelihood of shedding. Any effects of weaning or turnout were not statistically significant. It appears that the rate of shedding of VTEC O157 is influenced by several factors but possibly the most important of these are the circumstances of animals being housed, or, when outside, the presence of wild geese.

Estimation of malaria transmission from humans to mosquitoes in two neighbouring villages in south Cameroon: evaluation and comparison of several indices

Malaria transmission from humans to mosquitoes was assessed in two neighbouring villages in a rural area near Yaoundé, Cameroon during high and low transmission seasons during 1998–2000, using several indices previously evaluated in different areas endemic for malaria but never directly compared. These indices were estimated from human parasitological data and mosquito infection rates and, for each individual, thick blood films were prepared at the same time as experimental infection of laboratory-bred mosquitoes. Among the 685 volunteers examined, the prevalence of Plasmodium falciparum gametocyte carriers was 16%, and 8% of individuals were able to infect mosquitoes. The percentage of mosquitoes that became infected by feeding on the infectious individuals was 21 %. Children aged < 10 years contributed to about 75% of the infectious reservoir, although they constituted only 35% of the total population. Differences were found between the transmission seasons and the villages, and varied according to the index examined. Although there were more infectious individuals in one of the two villages, they were less infectious than those in the other village during the high transmission season. Comparative analysis of the transmission indices suggests the existence of functioning transmission-blocking immunity in one of the villages, which until now has been only hypothetically considered to play a role in malaria transmission in a natural setting. The epidemiological value of all the indices used and their accuracy in estimating the human infectious reservoir and its natural or induced variations are discussed.

Beliefs About Methadone in an Inner-City Methadone Clinic

Despite being considered both the most effective treatment for heroin addiction and an essential tool in the prevention of human immunodeficiency virus (HIV), methadone maintenance (MM) is often held in low esteem by heroin addicts-even those in MM treatment. This survey examined current beliefs and attitudes about MM of patients at an inner-city clinic, and the personal experience and attitudes of these patients with this treatment. Consenting patients in a methadone clinic serving a poor population with high rates of human immunodeficiency virus infection were queried about their attitudes toward and beliefs about methadone using a 16-item questionnaire. Over 2 days, 315 questionnaires were completed (acceptance rate 40%), totaling 32% of the 1,000 clinic patients. Nearly 80% believed that methadone had a positive effect on his or her life, but 80% were certain or unsure as to whether methadone is bad for one's health, and a similar percentage (80%) believed that discontinuing methadone was an important goal. Patients continue to have strongly negative attitudes toward and beliefs about methadone despite their acknowledgement that methadone has been very positive for them as individuals. As a result, many patients leave MM treatment prematurely, and there are usually unfilled slots in MM programs in New York City, even while continued need exists (e.g., less than 25% of the heroin addicts in the city are in treatment). The restrictive nature of many MM programs may account for these attitudes and beliefs.

Obtaining sensitive data through the Web: an example of design and methods.

Several studies have suggested that the quality of coital data from diaries is superior to that collected by retrospective questionnaires. By collecting data over short intervals of time, diaries can present a more comprehensive picture of exposure, while minimizing the potential for recall bias. Despite these advantages, paper diaries have limited use because of their expense and difficulty of implementation. Web-based data collection offers the opportunity to make improvements to the quality of epidemiologic exposure measurement by providing privacy and convenience to study participants while reducing costs associated with questionnaire administration and allowing for real-time data processing. We adapted coital diaries for Web-based data collection in a study of transmission rates of genital human papillomavirus infection among young adults. University women complete an online sexual behavior questionnaire ("diary") every 2 weeks over a 3-year follow-up period; men complete a single online sexual behavior questionnaire ("journal"). In this paper we describe the design, methodology and implementation issues that emerge in conducting a Web-based epidemiologic study. We also discuss compliance, as well as methods for assuring appropriate security, confidentiality and privacy.

Increased risk of parvovirus B19 infection in young adult cancer patients receiving multiple courses of chemotherapy.

An increased human parvovirus B19 infection rate has been observed in immunocompromised hosts. In this study, we sought to determine the prevalence of parvovirus B19 infection in adult cancer patients receiving multiple courses of systemic chemotherapy. From March 1999 through April 2000, 59 men and 68 women, with a median age of 49 (18 to 79) years, were enrolled in this study. They had received an average of 7.1 (4 to 32) courses of systemic chemotherapy. The median duration from the date of starting chemotherapy to the date of blood sampling was 11 (4 to 88) months. Serum B19 immunoglobulin G (IgG) and IgM levels were examined by an enzyme-linked immunosorbent assay, and B19 DNA was examined by a nested PCR. A group of 400 healthy blood donors served as the control group. The overall prevalences of anti-B19 IgG in adult cancer patients and healthy blood donors were 61.4 and 25.0%, respectively (P < 0.01). Anti-B19 IgM and B19 DNA were not detectable in these anti-B19 IgG-seropositive individuals. A further age-stratified comparison revealed that only patients younger than 40 years had a significantly higher anti-B19 IgG seropositivity rate than the controls (19 of 39 versus 53 of 310; P < 0.001). The increased prevalence of B19 infection in these 39 adult patients younger than 40 years might be clinically significant, since unexplained anemia, a common sequela of B19 infection, was detected in 3 of 20 seronegative patients (15.0%) and in 12 of 19 seropositive patients (63.2%) (P < 0.005). The results of this study suggest that adult patients younger than 40 years and receiving multiple courses of systemic chemotherapy may have a significantly increased risk of B19 infection. Prospective studies to define the time course and clinical consequence of B19 infection in this group of patients are needed.

Comparison between human and animal isolates of Shiga toxin-producing Escherichia coli O157 from Australia.

There is very little human disease associated with enterohaemorrhagic Escherichia coli O157 in Australia even though these organisms are present in the animal population. A group of Australian isolates of E. coli O157:H7 and O157:H- from human and animal sources were tested for the presence of virulence markers and compared by XbaI DNA macrorestriction analysis using pulsed-field gel electrophoresis (PFGE). Each of 102 isolates tested contained the gene eae which encodes the E. coli attaching and effacing factor and all but one carried the enterohaemolysin gene, ehxA, found on the EHEC plasmid. The most common Shiga toxin gene carried was stx2c, either alone (16%) or in combination with stx1 (74%) or stx2 (3%). PFGE grouped the isolates based on H serotype and some clusters were source specific. Australian E. coli O157:H7 and H- isolates from human, animal and meat sources carry all the virulence markers associated with EHEC disease in humans therefore other factors must be responsible for the low rates of human infection in Australia.

Pulmonary tuberculosis in pregnancy

Tuberculosis (TB) was once a formidable public health hazard but is now less feared because of the development of an armamentarium of effective drugs. The incidence of TB had been declining for decades until recently when the number of cases of TB began to rise. The most obvious reasons for this trend were the rising rate of human immunodeficiency virus infection and the development of multiple drug–resistant TB. The largest percentage increase in TB cases occurred among persons 25 to 44 years of age; many of them are women. A number of these women will first be diagnosed with TB infection during pregnancy. It is important for the clinician to be aware of the impact of TB on this population. Patients must be screened as recommended by the Centers for Disease Control and Prevention because it is important to quickly diagnose TB. Prompt and effective therapy will benefit the mother and the neonate. This article reviews the diagnosis, prevention, and treatment regimens of TB in pregnancy, as well as the effects on the HIV patient, the neonate, and breastfeeding. Prompt recognition and treatment of TB infection will ensure that the rates of TB cases decline.

Recent striking changes in histological differentiation and rate of human papillomavirus infection in squamous cell carcinoma of the lung in Okinawa, a subtropical island in southern Japan

Aims—The incidence of lung cancer in Okinawa has been the highest in Japan since 1975, and squamous cell carcinoma (SCC), especially the well differentiated form, is the most prevalent form...

An enzyme-linked immunosorbent assay for detection of IgG1 antibodies specific to human cystic echinococcosis in Egypt.

Human cystic hydatidosis (cystic echinococcosis) is a chronic zoonotic disease that results from infection with the dog tapeworm Echinococcus granulosus. In Egypt, cystic echinococcosis (CE) is recognized in slaughtered livestock by veterinarians, however, there is little information about human CE infection rates. We describe an immunological assay useful for the diagnosis of human cystic hydatidosis. Sera were collected from surgically confirmed hydatid cases (34), nonendemic subjects free from parasitic infection (20) and from subjects (109) infected with other helminths (Hymenolepis nana, Schistosoma mansoni, Fasciola hepatica and Ancylostoma duodenale). Hydatid cyst fluid (HCF) of camel origin was used as antigen in an ELISA format to measure total E. granulosus specific IgG antibodies and IgG subclasses. Sensitivity measurements of total IgG, and IgG1-4 were 100, 100, 79.4, 61.8 and 55.9%, respectively, whereas respective specificity reached 65.1, 97.7, 98.4, 96.1 and 83. 7%. The diagnostic value of measuring IgG1 (97.7%), as assessed by a rating index (J) for combined sensitivity and specificity, was superior to total IgG (65.1%) and IgG2-4 (77.8, 57.9 and 39.6%, respectively). These findings set the stage for field evaluation of the IgG1 assay in areas endemic with human cystic hydatidosis.

Influence of humans and domestic animals on the household prevalence of Trypanosoma cruzi in Triatoma infestans populations in northwest Argentina.

In three rural villages of northwest Argentina, the overall proportion of domiciliary Triatoma infestans infected with Trypanosoma cruzi was 49% among 1,316 bugs individually examined for infection in March and October 1992). Most of the variation among individual households in the proportion of infected triatomines was explained by variations among houses in the proportion of bugs that fed on dogs or cats, the prevalence of infected dogs or cats, and the proportion of bugs that fed on humans, according to a logistic multiple regression analysis. The effects of human infection rates on bug infection rates were not statistically significant. After adjusting for the effects of other predictors, the presence of chickens in bedroom areas had negative and significant effects on the proportion of infected Triatoma infestans, and positive and significant effects on the number of T. cruzi-infected triatomines collected per person-hr per house. Dog or cat infection rates and the proportion of bugs that fed on dogs or cats and on chickens explained 80% of the total variance of infected-bug numbers in a linear multiple regression model. This is the first study to use detailed field data to show that variations in triatomine infection rates depend on bug host feeding patterns and dog or cat infection rates, while the presence of chickens in bedroom areas exerts opposite effects on the proportion and number of infected triatomines. Domestic animals play a crucial role in the domiciliary transmission of T. cruzi.

Mathematical models of transmission dynamics and control of schistosomiasis.

Mathematical models are potentially valuable aids to a quantitative understanding of schistosome epidemiology and to the design of control programs. A basic theoretical framework is described that is developed to incorporate the impact of acquired immunity, heterogeneous transmission rates, and the effects of control measures. Models that assume that acquired immunity acts to moderate the rate of human infection make predictions consistent with age-intensity data from different human populations. Models incorporating heterogeneous water contact behavior can be applied to suitable field data and used to predict the potential efficacy of targeted chemotherapy or focal molluscicide application. More complex and detailed models can be used in simulation studies to assist with the design of field trials and in the interpretation of data from these trials. These applications of mathematical models suggest several areas requiring further theoretical development and also indicate areas in which adequate field data are still lacking.

Seasonal influence on human enteric infection by Ancylostoma caninum.

Ancylostoma caninum, the cosmopolitan canine hookworm prevalent in domestic pets throughout northeastern Australia, has been identified as a cause of obscure abdominal pain. To investigate the influence of climate on putative and confirmed human infections, a retrospective study of patients with eosinophilic enteritis and established infections was undertaken to identify the monthly and seasonal rates. The numbers seen each month were maintained throughout most of the year but decreased in June and remained low during winter. An increased rate of enteritis occurred during spring, which preceded the wet season. It is concluded that climate directly influences the rate of human enteric infection by canine hookworms. The increase in prevalence before the monsoon season was unexpected and suggests other influences, such as extraneous infection promoted by the irrigation of domestic gardens and possibly endogenous reinfection of the gut by hypobiotic larvae.

Predictors of high and low levels of HIV risk behavior among adults with chronic mental illness

Several recent studies confirm elevated rates of human immunodeficiency virus infection among acute and chronic mentally ill adults in large urban areas. This research sought to characterize risk for HIV infection among adults with chronic mental illness and to examine psychosocial factors predictive of risk. Two hundred and twenty-five adults with chronic mental illness who were sexually active in the past year outside of exclusive relationships were individually interviewed in community mental health clinics using a structured HIV risk assessment protocol. More than 50 percent of the study participants were sexually active in the past month, and 25 percent had multiple sexual partners during that period. Fifteen percent of the men had male sexual partners. In more than 75 percent of occasions of sexual intercourse, condoms were not used. When participants were categorized as at either high or lower risk for HIV infection based on their pattern of condom use, psychosocial factors that predicted risk level included measures of participants' self-reported efficacy in using condoms, perceptions of social norms related to safer sex among peers and sexual partners, and expectations about outcomes associated with condom use, as well as participants' level of objectively assessed behavioral skills in negotiation and assertiveness in sexual situations. Interventions aimed at prevention of HIV and AIDS are urgently needed in settings that provide services to persons with chronic mental illness.

Spectrum of genital human papillomavirus infection in a female adolescent population.

Human papillomavirus infection is a sexually transmitted disease associated with cervical dysplasia and carcinoma. To determine prevalence rates of cervical human papillomavirus infection compared with other sexually transmitted diseases and risk factors associated with human papillomavirus infection among adolescent women, we evaluated 634 patients attending three urban adolescent clinics. Patient evaluation included Pap smears; screening for chlamydia, gonorrhea, and trichomoniasis; and testing of cervical swab samples for human papillomavirus DNA. Cervical human papillomavirus was the most common STD in our population (15.6%), followed by infection with Chlamydia trachomatis (11.0%), Neisseria gonorrhoeae (7.1%), and Trichomonas vaginalis (5.4%). The most prevalent human papillomavirus types were 16/18 (7.3%), followed by 31/33/35 (4.7%) and 6/11 (3.5%). When genital warts on exam, low-grade squamous intraepithelial lesions on cytology, or cervical human papillomavirus DNA were considered as indicators of genital human papillomavirus infection, 24% of patients had any manifestation of infection, including 15% with clinically apparent infection (genital warts), 36% with cytologically apparent infection without warts, and 49% with subclinical infection only (cervical human papillomavirus DNA without low-grade squamous intraepithelial lesions or warts). Factors associated with detection of cervical human papillomavirus DNA by multivariate analysis included number of lifetime sexual partners and genital warts on exam. Cervical human papillomavirus infection was the most prevalent sexually transmitted disease among an ethnically diverse group of urban adolescent females, with a large proportion of infections neither clinically nor cytologically apparent. The strong association with lifetime sexual partners substantiates that cervical human papillomavirus is acquired predominantly by sexual contact and often soon after the onset of sexual activity.

Characteristics of cervical intraepithelial neoplasia in women infected with the human immunodeficiency virus

Our purpose was to compare characteristics of cervical intraepithelial neoplasia in relation to human immunodeficiency virus infection among women referred to a public hospital colposcopy clinic with Papanicolaou smears showing cervical intraepithelial neoplasia. An evaluation of cervical intraepithelial neoplasia severity, lesion size, and vulvovaginal lesions with respect to human immunodeficiency virus status was performed. (1) Human immunodeficiency virus prevalence in 482 women with cytologic characteristics of cervical intraepithelial neoplasia was 13%. (2) In human immunodeficiency virus-infected patients, Papanicolaou smears were less adequate for evaluation and correlated less well with histologic findings than in uninfected patients (p < 0.05). (3) Human immunodeficiency virus-infected patients (n = 47) had more advanced cervical intraepithelial neoplasia, larger cervical lesions, and more associated vulvovaginal lesions than human immunodeficiency virus-negative patients (n = 161). In human immunodeficiency virus-positive women, the severity of cervical intraepithelial neoplasia was not associated with age, whereas in human immunodeficiency virus-negative women, increasing severity was significantly associated with increasing age. High rates of human immunodeficiency virus infection in inner-city colposcopy services and high-grade, extensive cervical lesions in infected women warrant special attention.

Seroprevalence rates of human immunodeficiency virus infection at sentinel hospitals in the United States

Seroprevalence rates of human immunodeficiency virus infection at sentinel hospitals in the United States

Seroprevalence Rates of Human Immunodeficiency Virus Infection at Sentinel Hospitals in the United States

ST. LOUIS, M. E.; RAUCH, K. J.; PETERSEN, L. R.; ANDERSON, J. E.; SCHABLE, C. A.; DONDERO, T. J. AND THE SENTINEL HOSPITAL SURVEILLANCE GROUP Author Information

The Sexually Transmitted Disease Model for Cervical Cancer

The definition of cervical neoplasia as a sexually determined disease caused by some types of human papillomavirus has been widely accepted. Recent epidemiologic studies, however, have failed to identify a correlation between sexual activity and human papillomavirus infection. Moreover, sexual activity has also been shown to be independent of human papillomavirus infection in increasing cervical cancer risk. These incoherences are analyzed with respect to etiologic models for cervical neoplasia and by considering the role of misclassification of human papillomavirus infection in interpreting the relations assumed under these models. Even small levels of misclassification can considerably distort (1) the presumed prevalence of viral infection, (2) the association between sexual activity and human papillomavirus infection, and (3) the ability to control the relation between sexual activity and cancer by human papillomavirus infection. In field surveys, the presumed rates of human papillomavirus infection based on a DNA assay such as the filter in situ hybridization may be a gross overestimation of the true viral prevalence. Use of moderately misclassified human papillomavirus infection test results for effect estimation and covariate adjustment in data analysis may seriously distort the underlying relations. Consequently, considering these conditions, the apparent incoherence of recent epidemiologic findings should not be construed as evidence against the role of human papillomavirus in the etiology of cervical cancer or the validity of the sexually transmitted disease model.

Release and survival of Echinococcus eggs in different environments in Turkana, and their possible impact on the incidence of hydatidosis in man and livestock

In Turkana, Kenya, a prevalence of hydatidosis of nearly 10% has been recorded among the pastoralists yet their livestock have a much lower prevalence of the disease. The present study investigated the release from dogs and subsequent survival of Echinococcus eggs in Turkana huts, water-holes and in the semi-arid environment. The results were compared with the survival of eggs of Taenia hydatigena and T. saginata. The study was repeated under the cooler and moister conditions found in Maasailand where livestock have a greater incidence of hydatid disease than in Turkana but where the incidence in man is ten times lower. The average number of Echinococcus eggs per proglottid is 823. Nine percent of these remain in proglottids 15 minutes after release from a dog and the released eggs lose their viability in less than two, 48 and 300 hours in the sun, huts and water in Turkana respectively: the major influencing factor being temperature. The greater survival of eggs in the houses, coupled with the fact that dogs congregate for most of the day in the small houses facilitating a close man:dog contact, provide ideal conditions for the transmission of the parasite to man. The hostile environmental conditions and lack of contact between dogs and livestock contributes to the lower infection rate in livestock. Conversely in Maasailand, Echinococcus eggs survive in the environment for longer than three weeks and in addition, dogs are used for herding. This partly explains the higher infection rate among Maasai livestock but the low human infection rate remains arcane and requires further study.(ABSTRACT TRUNCATED AT 250 WORDS)