2008 outbreak of Salmonella Saintpaul infections associated with raw produce

BACKGROUND

Raw produce is an increasingly recognized vehicle for salmonellosis. We investigated a nationwide outbreak that occurred in the United States in 2008.

METHODS

We defined a case as diarrhea in a person with laboratory-confirmed infection with the outbreak strain of Salmonella enterica serotype Saintpaul. Epidemiologic, traceback, and environmental studies were conducted.

RESULTS

Among the 1500 case subjects, 21% were hospitalized, and 2 died. In three case-control studies of cases not linked to restaurant clusters, illness was significantly associated with eating raw tomatoes (matched odds ratio, 5.6; 95% confidence interval [CI], 1.6 to 30.3); eating at a Mexican-style restaurant (matched odds ratio, 4.6; 95% CI, 2.1 to ∞) and eating pico de gallo salsa (matched odds ratio, 4.0; 95% CI, 1.5 to 17.8), corn tortillas (matched odds ratio, 2.3; 95% CI, 1.2 to 5.0), or salsa (matched odds ratio, 2.1; 95% CI, 1.1 to 3.9); and having a raw jalapeño pepper in the household (matched odds ratio, 2.9; 95% CI, 1.2 to 7.6). In nine analyses of clusters associated with restaurants or events, jalapeño peppers were implicated in all three clusters with implicated ingredients, and jalapeño or serrano peppers were an ingredient in an implicated item in the other three clusters. Raw tomatoes were an ingredient in an implicated item in three clusters. The outbreak strain was identified in jalapeño peppers collected in Texas and in agricultural water and serrano peppers on a Mexican farm. Tomato tracebacks did not converge on a source.

CONCLUSIONS

Although an epidemiologic association with raw tomatoes was identified early in this investigation, subsequent epidemiologic and microbiologic evidence implicated jalapeño and serrano peppers. This outbreak highlights the importance of preventing raw-produce contamination.

One dose of varicella vaccine does not prevent school outbreaks: is it time for a second dose?

OBJECTIVES

The implementation of a routine childhood varicella vaccination program in the United States in 1995 has resulted in a dramatic decline in varicella morbidity and mortality. Although disease incidence has decreased, outbreaks of varicella continue to be reported, increasingly in highly vaccinated populations. In 2000, a varicella vaccination requirement was introduced for kindergarten entry in Arkansas. In October 2003, large numbers of varicella cases were reported in a school with high vaccination coverage. We investigated this outbreak to examine transmission patterns of varicella in this highly vaccinated population, to estimate the effectiveness of 1 dose of varicella vaccine, to identify risk factors for vaccine failure, and to implement outbreak control measures.

METHODS

A retrospective cohort study involving students attending an elementary school was conducted. A questionnaire was distributed to parents of all of the students in the school to collect varicella disease and vaccination history; parents of varicella case patients were interviewed by telephone. A case of varicella was defined as an acute, generalized, maculopapulovesicular rash without other apparent cause in a student or staff member in the school from September 1 to November 20, 2003. Varicella among vaccinated persons was defined as varicella-like rash that developed >42 days after vaccination. In vaccinated persons, the rash may be atypical, maculopapular with few or no vesicles. Cases were laboratory confirmed by polymerase chain reaction, and genotyping was performed to identify the strain associated with the outbreak.

RESULTS

Of the 545 students who attended the school, 88% returned the questionnaire. Overall varicella vaccination coverage was 96%. Forty-nine varicella cases were identified; 43 were vaccinated. Three of 6 specimens tested were positive by polymerase chain reaction. The median age at vaccination of vaccinated students in the school was 18 months, and the median time since vaccination was 59 months. Forty-four cases occurred in the East Wing, where 275 students in grades kindergarten through 2 were located, and vaccination coverage was 99%. In this wing, varicella attack rates among unvaccinated and vaccinated students were 100% and 18%, respectively. Vaccine effectiveness against varicella of any severity was 82% and 97% for moderate/severe varicella. Vaccinated cases were significantly milder compared with unvaccinated cases. Among the case patients in the East Wing, the median age at vaccination was 18.5 and 14 months among non-case patients. Four cases in the West Wing did not result in further transmission in that wing. The Arkansas strains were the same as the common varicella-zoster virus strain circulating in the United States (European varicella-zoster virus strain).

CONCLUSIONS

Although disease was mostly mild, the outbreak lasted for approximately 2 months, suggesting that varicella in vaccinated persons was contagious and that 99% varicella vaccination coverage was not sufficient to prevent the outbreak. This investigation highlights several challenges related to the prevention and control of varicella outbreaks with the 1-dose varicella vaccination program and the need for further prevention of varicella through improved vaccine-induced immunity with a routine 2-dose vaccination program. The challenges include: 1-dose varicella vaccination not providing sufficient herd immunity levels to prevent outbreaks in school settings where exposure can be intense, the effective transmission of varicella among vaccinated children, and the difficulty in the diagnosis of mild cases in vaccinated persons and early recognition of outbreaks for implementing control measures. The efficacy of 2 doses of varicella vaccine compared with 1 dose was assessed in a trial conducted among healthy children who were followed for 10 years. The efficacy for 2 doses was significantly higher than for 1 dose of varicella vaccine. This higher efficacy translated into a 3.3-fold lower risk of developing varicella >42 days after vaccination in 2- vs 1-dose recipients. Of the children receiving 2 doses, 99% achieved a glycoprotein-based enzyme-linked immunosorbent assay level of > or =5 units (considered a correlate of protection) 6 weeks after vaccination compared with 86% of children who received 1 dose. The 6-week glycoprotein-based enzyme-linked immunosorbent assay level of > or =5 units has been shown to be a good surrogate for protection from natural disease. Ten years after the implementation of the varicella vaccination program, disease incidence has declined dramatically, and vaccination coverage has increased greatly. However, varicella outbreaks continue to occur among vaccinated persons. Although varicella disease among vaccinated persons is mild, they are contagious and able to sustain transmission. As a step toward better control of varicella outbreaks and to reduce the impact on schools and public health officials, in June 2005, the Advisory Committee on Immunization Practices recommended the use of a second dose of varicella vaccine in outbreak settings. Early recognition of outbreaks is important to effectively implement a 2-dose vaccination response and to prevent more cases. Although the current recommendation of providing a second dose of varicella vaccine during an outbreak offers a tool for controlling outbreaks, a routine 2-dose recommendation would be more effective at preventing cases. Based on published data on immunogenicity and efficacy of 2 doses of varicella vaccine, routine 2-dose vaccination will provide improved protection against disease and further reduce morbidity and mortality from varicella.

Barriers to public health management of a pertussis outbreak in Arkansas

BACKGROUND

During the 2001-2002 respiratory season, Arkansas experienced one of its worst pertussis outbreaks. This crisis occurred shortly after the September 11, 2001, terrorist attacks.

OBJECTIVE

To determine whether vulnerabilities in the public health infrastructure existed in the context of emerging infectious diseases or possible bioterrorist attacks.

DESIGN

Key personnel involved in the Arkansas pertussis outbreak were interviewed, and health department epidemiologic data were reviewed.

SETTING

Observations were made for the statewide private-public management of the epidemic.

PARTICIPANTS

Physicians, infectious disease specialists, epidemiologists, field nurses, health department staff, laboratory staff, and administrators.

MAIN OUTCOME MEASURES

Diagnosis capability; vaccine, prophylaxis, and treatment programs; and effectiveness of global outbreak management.

RESULTS

Diagnosis of pertussis was a major barrier to management of the outbreak. The nonspecific clinical diagnosis, unreliability of testing methods, excessive number of samples, unavailability of reagents, and inadequate transport system, laboratory personnel, and equipment all impeded effective diagnosis. Vaccine shortage was not believed to contribute to the extent of the outbreak. Prophylaxis was problematic because of feared adverse effects of drugs and uncertainty about the efficacy of new drugs, but compliance was found to be good. From a public health perspective, isolation procedures, school absence policies, and health department referrals to private physicians all contributed to confusion. Problems with communications, staffing, and public cooperation were identified. Despite these barriers, the epidemic was well tolerated, with no known mortality and limited morbidity.

CONCLUSIONS

Despite many identified barriers to effective public health management, Arkansas tolerated its worst epidemic of pertussis in many years. However, were the state to experience an outbreak of a more pathogenic agent, introduced either naturally or of bioterrorist origin, these vulnerabilities could become critical. Natural outbreaks serve as excellent experiences on which to recognize and correct barriers to public health management.

Interaction of hypoxia and hypercapnia on respiratory drive in patients with COPD

The objective of this study was to compare the response of respiratory drive to progressive hypoxia under eucapnic and hypercapnic conditions in patients with severe COPD. Twenty-five patients with severe COPD and 13 nonsmoking young men were studied. The pressure in the occluded airway measured 0.1 second after the onset of inspiration was used as an index of respiratory drive. The occlusion pressure was measured at levels of SaO2 between 97 and 85 percent while eucapnic. The PETCO2 was then increased 10 mm Hg and the study repeated. The response of respiratory drive to hypoxia as measured by the slope of the regression line relating occlusion pressure to SaO2 was weak and variable in eucapnic hypoxia, and some subjects had no demonstrable response. When mild respiratory acidosis was created by increasing the PETCO2, the response to hypoxia was much greater and occurred in all subjects studied. Respiratory acidosis resulting from acute elevation of the PaCO2 greatly potentiates the increase in respiratory drive in response to hypoxia in normal subjects and in patients with severe COPD. Increase in occlusion pressure may occur with slight degrees of hypoxia when acute hypercapnia is present. These observations suggest that patients with acute respiratory failure complicating COPD, treated with controlled oxygen administration with only partial correction of hypoxia and continued respiratory acidosis, will have high respiratory drive.

Effect of nicotine chewing gum on plasma nicotine levels of cigarette smokers

This study was designed to determine whether the use of nicotine chewing gum modifies the inhalation and absorption of nicotine by cigarette smokers. Our subjects, 12 subjects who smoked cigarettes regularly, were studied for 4 days. On the first day, they smoked as usual, and on the second, third, and fourth days they also chewed a placebo gum, 2-mg nicotine gum, or 4-mg nicotine gum. They were instructed to smoke as usual throughout the study. Mean plasma nicotine concentration was 29.5 ng/ml with the placebo gum, 30.9 ng/ml with the 2-mg gum, and 40.7 ng/ml with the 4-mg gum. Peak carbon monoxide level was lower with nicotine gum than with placebo gum. Data indicate self-regulation of blood nicotine levels. The subjects appear to have compensated almost completely for the increased intake of nicotine from the 2-mg nicotine gum by decreasing the inhalation of tobacco smoke. Nicotine compensation provided by the 4-mg nicotine gum is only partial.

Amount of nicotine and carbon monoxide inhaled by smokers of low-tar, low-nicotine cigarettes

In 76 smokers, correlations between plasma nicotine and alveolar carbon monoxide levels of the individual smoker and the nicotine and CO yields of his cigarette were very poor. In 24 smokers of low-nicotine, low-tar cigarettes, mean alveolar CO levels did not differ from those of smokers of regular cigarettes. Mean plasma nicotine levels were lower in smokers of low-nicotine cigarettes, but a wide overlap of individual values occurred. The implication that an individual shifting to ultra-low-tar cigarettes reduces risks of cardiopulmonary disease is unwarranted.