Multi-state outbreaks of acute gastroenteritis traced to fecal-contaminated oysters harvested in Louisiana.

Norwalk-like viruses (NLVs), or small round structured viruses, are known to cause acute gastroenteritis associated with eating contaminated shellfish. Between 1993 and 1996, three oyster-related gastroenteritis outbreaks attributed to NLV occurred in Louisiana. Intensive trace-back and environmental investigations revealed that the overboard disposal of sewage by oyster harvesters into oyster-bed waters was the most likely source of contamination in at least two of the outbreaks. The small infectious dose of NLV, the large quantity of virus particles in stool, and the ability of oysters to concentrate virus particles suggest that oyster-related outbreaks will continue unless strong control measures are established. Efforts to halt improper sewage disposal in oyster-harvesting waters, including overboard sewage discharge, must be undertaken if future outbreaks are to be prevented.

Vibrio vulnificus infection reporting on death certificates: the invisible impact of an often fatal infection.

This study assessed accuracy of (a) recording Vibrio vulnificus infection on death certificates and (b) International Classification of Disease (ICD)-9 codes for V. vulnificus. Patients with microbiologically confirmed V. vulnificus infection were identified as part of co-ordinated surveillance in four USA Gulf Coast states between 1989 and 1993. Of 60 deaths, 51 death certificates were reviewed and V. vulnificus was recorded as the immediate cause of death on 11 (22%). There was no ICD-9 code for V. vulnificus infection, thus no patients had an ICD-9 code indicating V. vulnificus infection. Of 23 certificates where V. vulnificus was recorded on the death certificate, only 5 (22%) were coded for Gram-negative, septicaemia. This study highlights the importance of teaching physicians how to provide epidemiologically meaningful data on death certificates and the need for accurate ICD mortality codes.

Three summertime outbreaks of influenza type A.

In the Northern Hemisphere, sporadic cases of influenza occur during the summer, yet summertime outbreaks are rare. From 12 August through 2 September 1993, three influenza outbreaks in Louisiana were investigated using medical-record review, interviews, viral cultures, serology, and active surveillance for influenza-like illness in Louisiana. Attack rates in the outbreaks were 61% (69/114), 42% (24/57), and 45% (23/51). Viruses isolated were most closely related to influenza A/Beijing/32/92 (H3N2). The identification of influenza A as the cause of the first two outbreaks led to the recommendation for amantadine use in the third outbreak. Active surveillance did not detect any other outbreaks of influenza-like illness during August or September 1993. Out-of-season influenza A outbreaks can therefore occur when little influenza-like illness is present in a community. Evaluation of outbreaks of acute, febrile respiratory illness outside the influenza season should include this possibility, since rapid detection can lead to the timely use of amantadine or rimantadine.

An outbreak of Norwalk virus gastroenteritis associated with eating raw oysters. Implications for maintaining safe oyster beds.

OBJECTIVE: To determine the characteristics and the cause of an outbreak of gastroenteritis associated with eating raw oysters. DESIGN: Survey of groups of persons reporting illness to the health department after eating oysters; survey of convenience sample of oyster harvesters; and tracing of implicated oysters. SETTING: General community. MAIN OUTCOME MEASURES: Relative risk for illness after oyster consumption, source bed of contaminated oysters, presence of antibodies to Norwalk virus in serum, presence of a Norwalk virus in stool by direct electron microscopy and reverse transcription-polymerase chain reaction (RT-PCR), and DNA sequences of RT-PCR products. RESULTS: Seventy (83%) of 84 persons who ate raw oysters became ill vs three (7%) of 43 people who did not eat raw oysters (relative risk, 11.9; 95% confidence interval, 4.0 to 34.2). Eleven (79%) of 14 serum pairs had at least a fourfold increase in antibody to Norwalk virus. All 12 stool samples tested were positive by electron microscopy and/or RT-PCR for Norwalk virus. The RT-PCR products from all seven stool samples tested had identical DNA sequences. Implicated oysters were harvested November 9 through 13, 1993, from a remote oyster bed. Crews from 22 (85%) of 26 oyster harvesting boats working in this area reported routine overboard disposal of sewage. One harvester with a high level of antibodies to Norwalk virus reported having gastroenteritis November 7 through 10 and overboard disposal of feces into the oyster bed. CONCLUSIONS: This outbreak was caused by contamination of oysters in the oyster bed, probably by stool from one or more ill harvesters. Education of oyster harvesters and enforcement of regulations governing waste disposal by oyster harvesting boats might prevent similar outbreaks.

Evaluation of an intervention program for the control of an outbreak of shigellosis among institutionalized persons.

After control measures were initiated to stop an outbreak of shigellosis in an institution for the developmentally disabled, there was a sharp decline in the number of cases of Shigella sonnei infection. Among ill residents, those treated with antibiotics had shorter mean duration of diarrhea (2.4 vs. 4.5 days, P < .01) and were less likely to have stool cultures positive for shigellae 2-4 weeks after onset of diarrhea (0/25 vs. 5/19; relative risk [RR] = undefined; P = .02). The attack rate was higher in villages where segregation of ill residents was not practiced (46/73 vs. 53/155; RR = 1.8; 95% confidence limits [CL], 1.4, 2.4). In individual housing units where ill residents were not segregated (preintervention), a correlation was found between mean duration of diarrhea and unit attack rates (r = .88; 95% CL, 0.29, 0.99). A study of all 305 residents 10 weeks after the intervention began revealed no positive stool cultures.

An outbreak of hepatitis A associated with swimming in a public pool.

A multistate outbreak of hepatitis A was traced to a campground in Louisiana. Among 822 campers during one weekend, 20 developed hepatitis A. Case-patients ranged in age from 4 to 36 years; the highest attack rate (6.4%) was for children aged 5-9 years. A case-control study revealed that case-patients were more likely than controls to have swum in a public swimming pool on Saturday afternoon (19/19 vs. 26/38; odds ratio [OR], undefined; lower 95% confidence limit, 1.7). Case-patients were more likely than controls to have swum in the jacuzzi pool (16/19 vs. 10/26; OR, 8.0; 95% confidence interval, 1.5-47.1) or adult pool A (19/19 vs. 15/26; OR, undefined; lower 95% confidence limit, 2.6). Case-patients were also more likely to have swum for greater than 1 h and to have put their heads under the water. Because of the design of the filtering system of adult pool A, a cross-connection between a sewage line and the pool water intake line was possible. This outbreak may have been caused by transmission of hepatitis A through swimming; thus, swimming may serve as a mode of transmission of hepatitis A virus, especially among small children.

Communitywide outbreak of Legionnaires' disease associated with a grocery store mist machine.

From 10 October through 13 November 1989, 33 patients were hospitalized with legionnaires' disease in Bogalusa, Louisiana. A case-control study revealed case-patients were more likely than controls to have shopped at grocery store A (93% vs. 52%; odds ratio [OR], 11.6; 95% confidence interval [CI], 2.3-78.7) in the 10 days before illness. Among those who shopped at grocery store A, case-patients were more likely to shop for greater than 30 min (OR, 18.0; CI, 2.0-407.8) and to buy produce items located close to an ultrasonic mist machine (OR, 7.4; CI, 1.3-56.2). Employees of grocery store A were more likely than employees of other grocery stores in Bogalusa to have antibody titers of greater than or equal to 1:128 to Legionella pneumophila serogroup 1 (Lp-1; relative risk, 2.9; CI, 1.3-6.8). Lp-1 was isolated from water in the reservoir of the mist machine. The monoclonal antibody subtype of the isolate was identical to organisms identified in two patients. Viable Lp-1 was isolated from mist produced by the machine. Aerosols from a grocery store mist machine were the source of this outbreak.

Evaluation of an intervention program in the control of an urban outbreak of shigellosis.

Community-wide outbreaks of shigellosis are a persistent public health problem. We evaluated the effect of a household-based intervention program on the control of an urban outbreak of S. sonnei gastroenteritis. During the intervention we attempted to contact all households with culture-confirmed S. sonnei and provide education in methods to prevent spread of Shigella. Subsequently we conducted a survey of intervention (n = 43) and nonintervention (n = 33) households. We also conducted a serosurvey of children three to five years of age. The number of new cases of S. sonnei infection declined steadily over several months after the intervention began. Members of the intervention households were more knowledgeable about handwashing (rate ratio [RR] 4.7, 95% confidence interval [CI] = 2.1-10.8) and others methods of S. sonnei transmission and control than members of nonintervention households. However, intervention households had higher attack rates of Shigella-associated diarrhea in susceptible household members (RR 1.4, 95% CI = 1.0-2.0). During the intervention we were able to contact only 25% of households by the eighth day after onset of diarrhea in the index case, when 90% of intrahousehold transmission of Shigella had already occurred. Two months after the outbreak ended, 42% of children in the outbreak community had elevated antibody titers against S. sonnei; an additional 19% had borderline elevated titers. The intervention program improved knowledge but may have occurred too late to prevent intrahousehold transmission of Shigella. Exhaustion of susceptible hosts, rather than the education program, likely accounted for the decline in shigellosis cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Epidemiologic characteristics of human tularemia in the southwest-central states, 1981-1987.

From 1981 through 1987, a total of 1,041 cases of tularemia in humans were reported in Arkansas, Kansas, Louisiana, Missouri, Oklahoma, and Texas; this represents 60% of the cases reported in the United States during this same time period. The state of Arkansas reported the highest total (420 cases). Annual incidence rates per one million population ranged from 36.3 in Arkansas to less than 5.0 in Kansas, Louisiana, and Texas. Epidemiologic data were available for 1,026 cases. The majority of cases were white (88%) and male (75%). May, June, and July were the months of onset of symptoms for 52% of the cases. For the cases with known exposure history, 63% reported an attached tick and 23% had exposure to rabbits. Other animals associated with human infection were squirrels, cats, and raccoons. The case-fatality ratio was 2%. Public health efforts to prevent human tularemia cases in the six southwest-central states should focus on reducing exposure to ticks.

Vibrio gastroenteritis in Louisiana: a prospective study among attendees of a scientific congress in New Orleans.

The incidence of diarrhea associated with infection by Vibrio species was investigated among attendees at the 1986 Interscience Conference on Antimicrobial Agents and Chemotherapy held in New Orleans. Twelve percent of respondents reported diarrhea; the risk of diarrhea was significantly higher in those who ate raw or cooked oysters (relative risk = 1.5, P = .005). At least one Vibrio species was recovered from 51 (11%) of 479 persons submitting stool specimens; however, only 15 (29%) of those with a positive stool culture also reported diarrhea. Of the five Vibrio species identified, V. parahaemolyticus was most common and was most strongly associated with diarrhea. V. cholerae serogroup O1 was not isolated despite the occurrence of a cholera outbreak during the same time period in Louisiana. Cultures of raw and cooked seafood served in local restaurants yielded five different Vibrio species. Although asymptomatic passage of Vibrio organisms was common among persons eating seafood, the risk of Vibrio gastroenteritis was low.

Cholera on the Louisiana Gulf Coast: historical notes and case report.

A 67-year old woman was brought by ambulance to the hospital because of syncope and collapse. Forty-eight hours prior to the admission she ate some crabs with her husband. The morning of admission she awakened with massive, watery diarrhea followed by vomiting and shock. She was admitted to the intensive care unit with hypotension and bradycardia. She was resuscitated after a large volume of fluid was administered. Approximately 22 liters of fluids were administered in 24 hours. Stool cultures grew out Vibrio cholerae 01 biotype El Tor, serotype Inaba. She was treated with intravenous doxycycline. Her recovery was uneventful. The patient's husband had mild diarrhea, and Vibrio cholerae 01 biotype El Tor, serotype Inaba was cultured from his stool. Vibrio cholerae is endemic on the Louisiana Gulf Coast. The first cholera epidemic occurred in 1832. After a hiatus of about 100 years, cholera reappeared in Louisiana in 1978.

Cholera in Louisiana. Widening spectrum of seafood vehicles.

The largest cholera outbreak in the United States in over a century occurred in Louisiana from August through October 1986. Eighteen persons in 12 family clusters had stool culture or serologic evidence of infection with toxigenic Vibrio cholerae 0-group 1. Thirteen of these persons had severe diarrhea, and 4 required intensive care unit treatment. Although all 18 survived, 1 96-year-old woman with suspected cholera died shortly after hospital admission. A case-control study showed that case-patients were more likely than neighborhood control subjects to have eaten cooked crabs or cooked or raw shrimp during the week before illness. Case-patients who ate crabs were more likely than control subjects who ate crabs to have undercooked and mishandled the crabs after cooking. A third vehicle from the Gulf waters, raw oysters, caused V cholerae 01 infection in two persons residing in Florida and Georgia. All three seafood vehicles came from multiple sources. Stool isolates from the Louisiana case-patients were genetically identical to other North American strains isolated since 1973, but differ from African and Asian isolates. While crabs are the most important vehicle for V cholerae 01 infection in the United States, shrimp and oysters from the Gulf coast can also be vehicles of transmission. A persisting reservoir of V cholerae 01 along the Gulf coast may continue to cause sporadic cases and outbreaks of cholera in Gulf states and in states importing Gulf seafood.

Blastomycosis in Washington Parish, Louisiana, 1976-1985.

For the period 1976-1985, the authors attempted to identify all cases of blastomycosis in Louisiana and studied in detail one county (Washington Parish) suspected by local physicians of having an unusually high incidence of the disease. The mean annual incidence rates for Louisiana and for Washington Parish were 0.23 and 6.8 cases per 100,000 population, respectively. To the authors' knowledge, the rate for Washington Parish is the highest annual incidence rate documented for a population in a nonoutbreak setting. Among the 30 cases detected in Washington Parish, the age range was 3 weeks to 81 years. Five cases died; of these, one was an infant who may have been infected in utero, and another developed clinical symptoms compatible with adult respiratory distress syndrome. There was no geographic clustering among cases the authors investigated, and a case-control study failed to identify specific activities or host factors which may have predispose to infection. Washington Parish is probably a hyperendemic area for blastomycosis because environmental conditions are especially conducive to Blastomyces dermatitidis growth. The study suggests that most cases in Washington Parish were sporadically infected, and common-source exposures to B. dermatitidis with resultant clinical illness are rare even in hyperendemic settings.

Gastroenteritis in patients with stool isolates of Vibrio vulnificus.

Vibrio vulnificus, a marine Vibrio associated with severe extraintestinal infections, has not been previously implicated as a cause of infectious diarrhea. Three patients were identified with diarrheal illness from whom this organism was the sole pathogen recovered from cultured stool specimens. All three had eaten raw oysters within one week of becoming ill. These patients were all taking medication that reduces gastric acidity, two were heavy drinkers of alcohol, and one had unrecognized colon cancer; these factors may have predisposed to the development of disease. Clinicians should consider that V. vulnificus may be a cause of gastroenteritis in patients who have consumed raw oysters.

Vibrio vulnificus. Man and the sea.

To identify risk factors for Vibrio vulnificus infections, we performed a regional case-control study of 19 patients identified by isolates received at a state reference laboratory. Interviews with patients or surviving relatives and with three controls for each patient were compared in a matched analysis. Patients with V vulnificus wound infection were more likely than controls to have sustained a puncture wound while handling fresh seafood or to have been exposed to salt water. More patients with primary septicemia than controls had eaten raw oysters before the onset of illness. Other risk factors for septicemia included underlying liver disease, hematopoietic disorders, chronic renal insufficiency, use of immunosuppressive agents, and heavy alcohol consumption. Although V vulnificus infection is unusual, with a regional incidence of 0.8 per 100,000 population in this study, septicemia in the immunosuppressed patient is a devastating illness that can be prevented by not eating raw seafood.

Cholera on a Gulf Coast oil rig.

A single case of severe diarrhea on a floating Texas oil rig was followed two days later by what proved to be the largest outbreak of cholera in the United States in over a century. After isolation of toxigenic Vibrio cholerae El Tor Inaba of the typical United States phage type from the index patient's stool, the ensuing investigation detected 14 additional cases of cholera and one asymptomatic infection serologically. Infection was associated with eating rice on the oil rig on a particular day (P = 0.03) when an open valve permitted the rig's drinking-water system to be contaminated by canal water containing sewage (including that from the index patient) discharged from the rig. The rice had been rinsed in the contaminated water after cooking, and before being served it had been maintained at a temperature that allows V. cholerae 01 to multiply. Toxigenic V. cholerae 01 is persisting in the United States, and large common-source outbreaks of cholera can occur if proper sanitation is not maintained.

Isolation of nontoxigenic Vibrio cholerae O1 from a human wound infection.

Vibrio cholerae serotype O1 organisms that do not produce cholera toxin and, in fact, lack the genetic material encoding the enterotoxin have recently been detected in coastal regions of the United States. Although these organisms have been assumed to be nonpathogenic, they have been considered a potential reservoir of toxigenic V. cholerae. In 1979, nontoxigenic V. cholerae O1 was isolated from a leg wound of an accident victim residing in New Orleans. The only known risk factors of the patient, besides his debilitated condition, were alcoholism and the consumption of raw oysters before recognition of his wound infection. Coincident with the identification of the isolate from the leg wound, an identical nontoxigenic V. cholerae O1 isolate was cultured from the sewage system serving the residence of this patient. Nontoxigenic V. cholerae O1 seems to be capable of multiplying in human tissue and may produce extraintestinal infection. This indigenous inhabitant of temperate coastal regions may not be avirulent and may be of public health significance.

Viral hepatitis associated with day-care centers.

From September 1976 through March 1978, we investigated 11 outbreaks of non-B viral hepatitis associated with Louisiana day-care centers. The outbreaks included 168 cases, most of which were erroneously considered "sporadic" cases of non-B viral hepatitis prior to the investigations. Thirteen percent of all non-B viral hepatitis cases reported in the New Orleans metropolitan area during 1977 were associated with one of the outbreaks. Most of the cases in each outbreak and 85% overall were in older, usually adult, contacts of children attending the day-care centers. Within the household, parents appeared to be at greatest risk, particularly those who had 1- to 2-year-old children in the day-care center. Day-care center outbreaks of non-B hepatitis are easily overlooked and may be more widespread than is currently appreciated.