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PubMed1995

Evaluation of the magnitude of the 1993 hantavirus outbreak in the southwestern United States.

In May 1993, an outbreak of hantavirus pulmonary syndrome (HPS) in the southwestern United States was caused by the previously unrecognized Sin Nombre virus (SNV). Most HPS patients had an influenza-like prodrome, followed by rapid onset of pulmonary edema (fatality rate, 52%). To define the magnitude of the outbreak, patients with milder illnesses who sought medical care in the outbreak area during the outbreak period were assessed for infection with SNV. Of 299 study subjects, 43 had illnesses similar to the HPS prodrome. One laboratory finding, thrombocytopenia, was highly discriminatory between non-HPS patients (1%) and confirmed HPS patients (71%; P < .001) during the prodrome phase. No study subject had serologic evidence (IgM antibodies) of recent SNV infection. Five had IgG titers consistent with a previous hantavirus infection: 3 of these 5 were among the 43 patients who had illnesses similar to the HPS prodrome (P < .05). These data provide evidence that mild illness is rarely caused by SNV.

Adolescent↗

PubMed1995

Virologic features of an astrovirus diarrhea outbreak in a day care center revealed by reverse transcriptase-polymerase chain reaction.

Astroviruses cause outbreaks of diarrhea in children attending day care centers (DCCs). Reverse transcriptase-polymerase chain reaction (RT-PCR) was compared with EIA detection of astrovirus in stool specimens to characterize further the molecular epidemiology of an outbreak of astrovirus-associated gastroenteritis. Three hundred sixty-eight stool specimens collected prospectively from 36 children enrolled in a DCC during an 11-week outbreak of diarrhea were evaluated by EIA and RT-PCR. Astrovirus was detected in 32% of specimens by RT-PCR versus 10% by EIA (P < .001) and in 89% of children by RT-PCR versus 50% by EIA. The median duration of astrovirus excretion episodes detected by EIA was 1.5 days versus 4 days by RT-PCR (P = .06). Astrovirus was excreted for prolonged periods by immunocompetent children during this outbreak. RT-PCR was more sensitive than EIA for detection of astrovirus in stool specimens and redefined the epidemiology of astrovirus infection in this setting.

Age Factors↗

PubMed1996

High-resolution genotyping elucidates the epidemiology of group A streptococcus outbreaks.

Streptococcus pyogenes strains were genotyped by a combination of molecular methods for high- resolution epidemiologic studies of disease outbreaks. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the emm gene is reported. Alone or in conjunction with other molecular techniques (16S ribotyping, pulsed-field gel electrophoresis, and detection of exotoxin genes), PCR-RFLP could differentiate outbreak-related strains from contemporaneous background strains of the same M serotype. Three outbreaks were studied: pharyngitis in a boarding school (serotype M5), cross-infection in a hospital burn unit (serotype M76), and severe invasive disease in two elderly care homes (serotype R28). It was possible, for example, to identify within serotype R28 a clone with particular potential for invasive disease. In all cases, the four molecular methods yielded complementary results that were hierarchically related. Strains could be assigned to the outbreak or the background in a precise, reproducible, and rapid manner.

Antigens, Bacterial↗

PubMed1996

Rapid determination of outbreak-related strains of Neisseria meningitidis by repetitive element-based polymerase chain reaction genotyping.

Outbreaks of invasive disease caused by Neisseria meningitidis have increased in the United States in the 1990s. Repetitive element-based polymerase chain reaction (rep-PCR), a recently developed genotyping method, was used to evaluate a group of 8 outbreak-related and 35 other meningococcal isolates previously typed by multilocus enzyme electrophoresis (MLEE). All were serogroup B or C. Sets of genotypes were generated using primers based on either of two different repetitive sequences. Genotype sets were analyzed in a blinded fashion. Each set correctly identified outbreak-related isolates. Among the other 35 isolates, rep-PCR delineated 14 and 13 strains, respectively, in the two sets of genotypes. Seventeen electrophoretic types had been delineated by MLEE. Rep-PCR holds promise as a rapid, genome-based typing method for delineation of apparent outbreaks of meningococcal disease.

Disease Outbreaks↗

PubMed1996

An outbreak of pruritic skin lesions in a group of laboratory workers--a case report.

In May 1993, an outbreak of pruritic skin lesions occurred among a group of employees located in four laboratories in the basement of an office building. Medical interviews with the affected workers were performed and an industrial hygiene survey of the site was conducted. Workers commonly reported a pricking sensation on exposed skin. Four of the workers had small (< 5mm) erythematous papules on their forearms. Just prior to the outbreak, the installation of fibrous glass insulation had commenced in the mechanical rooms which provided air to the basement of the building. Because of the nature of the symptoms and the temporal relationship with the nearby insulation work, direct skin contact with fibrous glass fibres was thought to be the cause of the outbreak. The poorly maintained air handling unit supplying air to the laboratories probably contributed to this outbreak by inefficient filtering of the circulating air.

Disease Outbreaks↗

PubMed1996

Impact of institution size, staffing patterns, and infection control practices on communicable disease outbreaks in New York State nursing homes.

Institutional risk factors associated with the occurrence of nosocomial respiratory or gastrointestinal disease outbreaks in 1992 were examined in a case-cohort study of New York State nursing homes conducted in 1993. Facility size, staffing patterns, and employee sick leave policies were the principal effects found in an unconditional logistic regression model. The risk of having respiratory or gastrointestinal disease outbreaks was greater in larger nursing homes (adjusted risk ratio (RR) = 1.71 for each 100-bed increase in size, 95% confidence interval (CI) 1.20-2.42), for nursing homes with a single nursing unit (adjusted RR = 3.93, 95% CI 0.98-15.71), or those with multiple nursing units with shared staff (adjusted RR = 2.51, 95% CI 1.07-5.89). The risk was less for nursing homes with paid employee sick leave policies (adjusted RR = 0.38, 95% CI 0.15-0.99). Other potential risk factors examined in this study, such as the ratio of beds per unit, type of sponsorship, daily review of laboratory test results, and the proportion of private beds and patient-to-staff ratio, were not significantly associated with the risk of disease outbreaks. The results of this study have direct implications for control of nosocomial disease outbreaks in nursing homes.

Aged↗

PubMed1996

Effectiveness of contact isolation during a hospital outbreak of methicillin-resistant Staphylococcus aureus.

Contact isolation has been recommended by the Centers for Disease Control and Prevention for the prevention of nosocomial transmission of methicillin-resistant Staphylococcus aureus (MRSA), but there are few data which prospectively quantitate the effectiveness of contact isolation for this purpose. During an outbreak of MRSA in a neonatal intensive care unit between July 18, 1991 and January 30, 1992, weekly surveillance cultures were performed on all patients. Sixteen of 331 admissions became colonized with MRSA, and 3 (19%) developed infections: bacteremia, conjunctivitis, and dialysis catheter site infection. The isolates from all 16 patients were submitted to plasmid profile analysis and restriction enzyme analysis of whole cell DNA. All of the patients had identical chromosomal patterns and plasmid profiles, which differed from control isolates from other wards, indicating that the outbreak resulted from spread of a unique strain. None of 144 personnel who were cultured after recent contact with newly colonized patients during the outbreak were found to carry MRSA, which suggests that patients were the reservoir for transmission rather than caregivers. The most probable source for each individual transmission was determined based on proximity in time and space and shared exposure to caregivers. The rate of transmission of MRSA from patients on contact isolation was significantly lower (0.009 transmissions per day on isolation) than the rate for patients not on isolation (0.140 transmissions per day unisolated, relative risk = 15.6, 95% confidence interval 5.3-45.6, p < 0.0001). The authors conclude that the risk of nosocomial transmission of MRSA was reduced 16-fold by contact isolation during the outbreak in this neonatal intensive care unit. These data confirm the results of previous studies which have suggested that contact isolation was effective in controlling the epidemic spread of methicillin-resistant Staphylococcus aureus.

Contact Tracing↗

PubMed2000

Measles outbreak in a northern Pakistani village: epidemiology and vaccine effectiveness.

In the spring of 1990, local community health workers reported a measles outbreak in several partially vaccinated villages in the Punial Valley in northern Pakistan. The authors conducted an investigation in one of these villages to assess vaccine coverage and vaccine efficacy and to describe the patterns of measles outbreaks that prevailed in this community. The results of a survey of the entire village revealed two major gaps in vaccine coverage: the small minority Sunni community and children over 3 years of age. Vaccine efficacy was estimated to range from 73 to 90% but was markedly reduced in children who were vaccinated under 12 months of age. The occurrence of an outbreak in a community in which a relatively new vaccination program is primarily directed at younger children has been predicted by theoretical models of measles dynamics and is consistent with the experience of other vaccination programs in the developing world. These observations suggest that, in some areas of the developing world, the age groups targeted to receive measles vaccinations may need to be broadened to ensure adequate coverage to prevent recurrent outbreaks.

Adolescent↗

PubMed1977

Foodborne hepatitis A infection: a report of two urban restaurant-associated outbreaks.

The cities of Portland, Oregon, and Buffalo, New York, each experienced a restaurant-associated foodborne outbreak of viral hepatitis type A during 1975. Although there were several food handlers ill with viral hepatitis A in each of the restaurants involved, each outbreak was the apparent result of food contamination by a single food handler. In the Buffalo outbreak, food contamination was documented to have occurred for a brief period of time six days prior to onset of any symptoms in the index case. These outbreaks point out the uncommon occurrence of food contamination by individuals ill with type A viral hepatitis, the usefulness of two types of food questionnaires in identifying the vehicle(s) of transmission, and the apparent lack of benefit of widespread immune serum globulin administration as a control measure in this setting.

Adult↗

PubMed1981

Transmission of multiple drug-resistant tuberculosis: report of a school and community outbreak.

An outbreak of tuberculosis in 1976 was caused by mycobacteria resistant to isoniazid (INH), streptomycin (SM), and para-aminosalicylic acid (PAS). High rates of infection associated with exposure to the index case suggested that transmission of resistant organisms had occurred, and the subsequent appearance of bacteriologically proven INH-SM-PAS-resistant tuberculosis in four school contacts of the index case confirmed this fact. Retrospective investigation revealed that the school outbreak was part of an ongoing community outbreak dating back at least to 1964. Through the use of case histories, drug-susceptibility patterns, and phage typing, 15 documented and seven presumed INH-SM-PAS-resistant, epidemiologically linked cases were found; two of these persons died of tuberculosis. Six additional cases with INH-SM-PAS resistance that could not be epidemiologically linked to the outbreak were also identified. The potential of drug-resistant strains for causing disease in humans should not underestimated.

Adolescent↗

PubMed1981

An outbreak of salmonellosis involving multiple vehicles.

A biphasic outbreaks of salmonellosis affected customers and employees of a restaurant in Maine, in October and November, 1979. Salmonella typhimurium was isolated from 27 customers and nine employees. Ten other individuals were ill but did not have specimens taken for culture, and there were four secondary cases including one affecting a laboratory technician. Fourteen individuals (28%) were hospitalized for up to 45 days, and a total of 416 days of work were lost as a result of the outbreak. Two different food items served at the restaurant at separate times were identified as vehicles. In the first part of the outbreak, 37 persons who consumed either egg-based foods (p = 0.003) or salad (p = 0.006) became ill. In the second phase of the outbreak, in late October and November, nine cases were associated with consumption of inadequately refrigerated salad (p = 0.008), but not with egg-based foods. An infected symptomatic food handler prepared the incriminated salad for some members of this latter group. Use of antacids was also associated with illness (p = 0.03). The occurrence of illness over a seven-week period, the implication of several vehicles, and the demonstration of secondary cases suggest that "sporadic" cases of salmonellosis in the community may be linked.

Adolescent↗

PubMed1982

An outbreak of acute nonbacterial gastroenteritis in a nursing home. Demonstration of person-to-person transmission by temporal clustering of cases.

An outbreak of acute nonbacterial gastroenteritis occurred among residents and staff in a nursing home in Baltimore, Maryland, in December 1980. A total of 101 residents and 69 staff members were surveyed by questionnaire. The attack rate (defined as acute onset of vomiting or two or more loose stools per 24 hours) was 46% in each group. Illness was brief and mild; no patients were hospitalized, and there were no deaths. Person-to-person transmission was documented by temporal clustering of cases (the demonstration of higher rate of illness among residents exposed to an ill roommate one or two days earlier than among those not similarly exposed; relative risk = 3.74), by a higher rate of illness among employees having daily contact with residents than among those without such contact (57% vs. 17%, p less than 0.01), and by secondary transmission to household contacts of ill employees (secondary attack rate = 33%). Three of 11 serum pairs from patients demonstrated a fourfold increase in antibody titer to the Norwalk virus between acute- and convalescent-phase specimens. The analysis of temporal clustering of cases was particularly useful in documenting person-to-person transmission in this outbreak and might be used for this purpose in other outbreaks caused by Norwalk or Norwalk-like viruses, as well as in outbreaks associated with other infectious organisms.

Aged↗

PubMed1988

Two outbreaks of trichinosis caused by horsemeat in France in 1985.

Two outbreaks of trichinosis occurred in France in August and October of 1985 and 1,073 cases in all were identified. In the first outbreak, two localities were involved: the town of Melun and the 14th district of Paris. To determine the origin of the contamination, three case-control studies were carried out: among patients' families, among the populations of these two areas, and among the inmates in the prison of Melun. In the second outbreak, cases again occurred in Paris but in a different district (the 12th), in the city's suburbs, and in other towns scattered throughout France. Although no parasites were found in any of the meat examined in either outbreak, results of the study indicate that infection was due to horsemeat consumption and led to the incrimination of two carcasses, one imported from a slaughterhouse in the United States and the other from West Germany. These findings led the French Ministry of Agriculture to order the inspection for trichinosis of all meat from horses slaughtered both in France and in countries exporting horsemeat to France.

Adolescent↗

PubMed1989

Hepatitis A outbreak on a floating restaurant in Florida, 1986.

In April and May 1986, the largest reported foodborne outbreak of hepatitis A in Florida state history occurred among patrons and employees of a floating restaurant. A total of 103 cases (97 patrons and six employees) were identified. The exposure period lasted 31 days (March 20-April 19), making this the most prolonged hepatitis A outbreak to occur in a restaurant that to date has been reported to the Centers for Disease Control. The exposure period was divided into time intervals (peak, early, late, and total) for calculation of food-specific attack rates. The authors showed that green salad was an important vehicle of transmission for each phase of the exposure period, with the highest adjusted odds ratio for the three-day peak exposure interval (March 28-30), 6.8 (p = 0.001). Non-salad pantry items and mixed bar drinks were also identified as vehicles of transmission; both were more important during the early interval of the exposure period than during the late interval. Two of six infected employees worked in the pantry and may have sequentially infected patrons. Though rare, this outbreak suggests that hepatitis A infection among employees may allow for transmission to patrons for prolonged periods of time. Prevention of such outbreaks requires prompt reporting of ill patrons with rapid identification of infected employees and correction of food handling practices.

Adolescent↗

PubMed1989

Role of Norwalk virus in two foodborne outbreaks of gastroenteritis: definitive virus association.

Two separate food-associated outbreaks of gastroenteritis occurred among Erie County, New York residents in June 1986. In one outbreak, cases of illness were estimated to have occurred in 50% of the approximately 700 persons in 13 groups who ate at an out-of-county restaurant during a seven-day period, and, in the second outbreak, illness occurred in 26 (30%) of 87 persons who attended a graduation party held in a private home. Laboratory investigation included serology (blocking radioimmunoassay) to determine seroconversion to Norwalk virus and an enzyme immunoassay for detection of Norwalk virus antigen in stools, which the investigators have found to be more specific for Norwalk virus than serology. Seroconversion to Norwalk virus occurred in 11 (79%) of 14 restaurant-related cases and seven (100%) of seven graduation party cases. Seroconversion to Norwalk virus antigen was also found in four (40%) of 10 food handlers at the restaurant and in two (100%) of two food handlers at the graduation party. Antigen was detected in the stools of three (20%) of 15 restaurant-related cases and four (67%) of six graduation party cases. No stools for viral analyses were available for testing from food handlers. All seven of the patients with Norwalk virus-positive stools were also positive by seroconversion. Widespread availability of reagents for stool antigen detection would result in confirmation of more outbreaks due to Norwalk virus and in a more timely manner.

Disease Outbreaks↗

PubMed1989

An explosive point-source measles outbreak in a highly vaccinated population. Modes of transmission and risk factors for disease.

In 1985, 69 secondary cases, all in one generation, occurred in an Illinois high school after exposure to a vigorously coughing index case. The school's 1,873 students had a pre-outbreak vaccination level of 99.7% by school records. The authors studied the mode of transmission and the risk factors for disease in this unusual outbreak. There were no school assemblies and little or no air recirculation during the schooldays that exposure occurred. Contact interviews were completed with 58 secondary cases (84%); only 11 secondary cases (19%) of these may have had exposure to the index case in the classrooms, buses, or out of school. With the use of the Reed-Frost epidemic model, only 22-65% of the secondary cases were likely to have had at least one person-to-person contact with the index case during class exchanges, suggesting that this mode of transmission alone could not explain this outbreak. A comparison of the first 45 cases and 90 matched controls suggested that cases were less likely than controls to have provider-verifiable school vaccination records (odds ratio (OR) = 8.1) and more likely to have been vaccinated at less than age 12 months (OR = 8.6) or at age 12-14 months (OR = 7.0). Despite high vaccination levels, explosive measles outbreaks may occur in secondary schools due to 1) airborne measles transmission, 2) high contact rates, 3) inaccurate school vaccination records, or 4) inadequate immunity from vaccinations at younger ages.

Adolescent↗

PubMed1995

Epidemiology of smallpox in west Pakistan. III. Outbreak detection and interlocality transmission. 1971.

During one year, 121 outbreaks of variola major were detected in 99 of the 1717 localities within a rural area of West Pakistan with a total population of approximately 1.2 million. Only 19% of the outbreaks, representing 36% of the 1040 investigated cases, were officially reported, although potential strengths in the government surveillance system were also identified. Persistence of smallpox within the area depended on introductions from the outside, and more than one-half of all outbreaks of known source could be ultimately traced to cities. Within the study area, outbreaks with the largest numbers of cases and those in the larger communities were the ones from which smallpox was most frequently transported. The frequency with which variola was introduced into localities was directly related to population size and to the presence of medical care facilities. Trips between localities by infected individuals were extremely rare events. They were made most often during the late fall and winter, primarily during the incubation period of the disease, and did not differ in purpose, means or destination from journeys unassociated with smallpox. Individuals at relatively high risk of becoming introducers included the unvaccinated (primarily children under five), the unschooled and those not native to the area. Vaccination priorities based on these findings could increase the efficiency of smallpox eradication efforts.

Disease Outbreaks↗

PubMed1996

An outbreak of bovine tuberculosis in two herds in south west Scotland--veterinary and human public health response.

BACKGROUND: Although the incidence of bovine tuberculosis in UK cattle has declined markedly, outbreaks still occur. There is often confusion as to how veterinary and human public health agencies should interact in such circumstances. We report an outbreak of bovine tuberculosis which occurred in South West Scotland in 1992. METHODS: The outbreak, which affected two cattle herds, and potentially involved 17 humans, was discovered when visible tuberculous lesions were found at routine post mortem examination of a calf. Investigation of animals and humans, exchange of information between human and veterinary public health agencies, and subsequent control measures followed the guidance of a recently produced protocol. RESULTS: Tuberculin testing of other animals in the index herd revealed 11 reactors. Testing of the herd of origin of these animals revealed 84 reactors out of 261 animals. Movement restrictions were placed on the index herd, and all the animals in the herd of origin were slaughtered. The humans were screened primarily by history and tuberculin skin testing. Eleven of them required chest X-rays (all were normal) and six were given prophylactic chemotherapy with isoniazid. Nobody developed clinical illness. CONCLUSION: The use of an agreed protocol proved to be very helpful to both human and veterinary public health agencies in the investigation and control of an outbreak of bovine tuberculosis. There is a clear need for better human screening tests.

Adult↗