Impact of anti-vaccine movements on pertussis control: the untold story.

To assess the impact of anti-vaccine movements that targeted pertussis whole-cell vaccines, we compared pertussis incidence in countries where high coverage with diphtheria-tetanus-pertussis vaccines (DTP) was maintained (Hungary, the former East Germany, Poland, and the USA) with countries where immunisation was disrupted by anti-vaccine movements (Sweden, Japan, UK, The Russian Federation, Ireland, Italy, the former West Germany, and Australia). Pertussis incidence was 10 to 100 times lower in countries where high vaccine coverage was maintained than in countries where immunisation programs were compromised by anti-vaccine movements. Comparisons of neighbouring countries with high and low vaccine coverage further underscore the efficacy of these vaccines. Given the safety and cost-effectiveness of whole-cell pertussis vaccines, our study shows that, far from being obsolete, these vaccines continue to have an important role in global immunisation.

Hospitalizations involving gastroenteritis in the United States, 1985: the special burden of the disease among the elderly.

While diarrheal disease is a well-recognized problem in children, its impact in the elderly has not been adequately assessed. Among the 4.06 million hospitalizations in 1985 in the McDonnell-Douglas Health Information System database, 98,185 hospitalizations, including 1,130 deaths, had gastroenteritis recorded as a discharge diagnosis. The authors analyzed the 87,181 hospitalizations and 514 deaths for which gastroenteritis was one of the top three diagnoses. Gastroenteritis was among the top three diagnoses in 9% of all hospitalizations of children 1-4 years of age, compared with 1.5% of hospitalizations throughout adulthood (greater than or equal to 20 years). Only 0.05% of hospitalizations involving gastroenteritis were fatal for children younger than 5 years, compared with 3% in individuals 80 years or older. While children aged less than 5 years and adults aged 60 years or more each comprised one-fourth of hospitalizations involving gastroenteritis, the older group represented 85% of diarrheal deaths. Age was the most important risk factor for death subsequent to a hospitalization involving gastroenteritis (odds ratio = 52.6, 95% confidence interval 37.0-76.9 for age greater than or equal to 70 years vs. less than 5 years). Gastroenteritis is a large, underemphasized public health problem among the elderly, among whom its case-fatality ratio is higher than in children.

Diarrheal deaths in the United States, 1979 through 1987. A special problem for the elderly.

OBJECTIVE: --Diarrhea is an important cause of death among young children in both developing and developed countries, but little is known about diarrheal death among adults. In this study, we examined trends in diarrheal deaths among all age groups in the United States. DESIGN/SETTING/PARTICIPANTS: --We reviewed national mortality data complied by the National Center for Health Statistics, Hyattsville, Md, which consists of information from all death certificates filed in the United States for the period 1979 through 1987. A death for which diarrhea was listed as an immediate or underlying cause was considered a "diarrheal death" and included in the analysis. RESULTS: --We found that 28,538 persons died of diarrhea cited as either an immediate or the underlying cause of death during the 9-year period. A majority of diarrheal deaths occurred among the elderly (older than 74 years of age, 51%), followed by adults 55 to 74 years of age (27%), and young children (younger than 5 years of age, 11%). For the elderly, adjusted risk factors for dying of diarrhea included being white, female, and residing in a long-term care facility. Only the elderly and young children had clear, distinct winter peaks of diarrheal deaths, suggesting that the diarrhea may, in part, be infectious in origin. CONCLUSION: --For the elderly, more directed studies of those at risk, such as nursing home residents, are needed to determine if oral rehydration therapy, vaccines, or other preventive measures might benefit this population.

Estimates of morbidity and mortality rates for diarrheal diseases in American children.

Although the importance of diarrhea as a prime cause of morbidity and death in developing countries is well recognized, the disease burden in the United States has never been thoroughly examined. We have prepared national estimates of the annual number of cases of diarrhea in children less than 5 years of age and of the outcome, measured in terms of visits to a physician, hospitalizations, and deaths. The annual number of diarrheal episodes was estimated by reviewing longitudinal studies of childhood diarrhea conducted in the United States and extrapolating these data to the nation. Estimates of physician visits, hospitalizations, and deaths were prepared from a variety of national data sources. We estimate that 16.5 million children less than 5 years of age have between 21 and 37 million episodes of diarrhea annually. Of these, 2.1 to 3.7 million episodes lead to a physician visit, a total of 220,000 patients are hospitalized, and 325 to 425 children die. The major cost of diarrhea lies in the high numbers and cost of hospitalizations, because approximately 10.6% of hospitalizations in this age group are for diarrhea. Diarrheal deaths occur in relatively small numbers, are more common in the South and among black persons, are potentially avoidable, and could represent as much as 10% of the preventable postneonatal infant death in the United States. These estimates underscore the extensive burden of diarrheal illness in children in the United States and suggest that interventions to prevent disease or decrease its severity could be cost-effective.

Operational safety issues in MRI.

The clinical usefulness of a diagnostic modality is weighed by considering its potential diagnostic benefit against its potential risk for a patient in question. Magnetic resonance imagining appears to offer both high efficacy and safety under most circumstances. Our understanding of the conditions under which MRI is safe and effective has undergone continual refinement with technological advances and clinical experience. The early emphasis on safety issues of MR focussed on consideration of bioeffects of RF and magnetic fields. More recently, hundreds of operating clinical MR sites, performing hundreds of thousands of clinical examinations to date, have provided a greater awareness of operational safety issues. Much of this experience is summarized in device labeling provided by manufacturers of MR devices, summaries prepared by regulatory agencies, and case reports in the medical literature. The purpose of this article is to review a broad range of safety considerations involved in the operation of MR imagers. The discussion is in two parts: (1) a short update of reported incidents and (2) an analysis of safety issues.

The MR appearance of CSF flow in patients with ventriculomegaly.

The purpose of this study was to investigate the MR imaging appearance of mobile CSF in the ventricular system in patients with ventriculomegaly caused by brain atrophy and extraventricular obstructive hydrocephalus. Pulsatile CSF often has decreased intensity relative to less mobile areas of CSF, particularly on T2-weighted scans. At times, the flow-related signal dropout causes striking heterogeneity in the appearance of CSF. This has been termed the CSF flow-void sign (CFVS) and is most likely caused by spin-phase shifts and time-of-flight effects created as a result of CSF turbulence and increased velocity of CSF pulsatile flow. The effect is most pronounced in areas where a larger volume of CSF moves through a small channel or foramen, such as the aqueduct of Sylvius or foramen of Magendie. The scans of 40 patients with ventriculomegaly caused by brain atrophy or extraventricular obstructive hydrocephalus were reviewed for the presence of the CFVS. All patients had the CFVS in the aqueduct of Sylvius on T2-weighted spin-echo sequences. The sign was present in the fourth ventricle in 96%, in the third ventricle in 70%, in the foramen of Magendie in 65-77%, and in the foramina of Monro in 33%. The sign was more pronounced in patients with larger ventricles but could not be used to differentiate patients with brain atrophy from those with extraventricular obstructive hydrocephalus.

Physiology of the CSF flow-void sign: modification by cardiac gating.

Low-intensity signal seen within areas of narrowing within the ventricular system has been termed the CSF flow-void sign. This decreased signal is related to CSF flow and turbulence. Seven normal volunteers were examined, and the changes that occurred in the appearance of the CFVS were noted when data acquisition was modified by cardiac gating. Flow-void patterns within the internal cerebral veins and basilar artery were also examined. The results of this study confirm that CSF flow is related to cardiac systole and diastole. An increase in hypointensity is seen in the areas of the aqueduct of Sylvius and the foramen of Magendie during the time at which the systemic arterial pulse wave is transmitted into the brain. The physiology of this observation is related either to a direct hydraulic effect of the venous system on the CSF or to filling and expansion of the thin-walled cerebral venous system. Hypointensity or an increase in the width of the basilar artery and internal cerebral veins during systolic data acquisition was also noted. The mechanism of this phenomenon is related to propagation of the systemic arterial pulse wave.

MR artifacts: a review.

The process of creating MR images frequently gives rise to artifacts in the final display. Many artifacts may be corrected or ameliorated through an understanding of their cause. This requires familiarity with scanner design; theory of operation; and image acquisition, generation, and display. Some artifacts are obvious, totally degrading the image; others are regional, leaving much of the scan undisturbed. In some cases, the degradation is permanent; in others, the data can be reprocessed or manipulated to yield artifact-free images. Some artifacts are overt and easily identified. Others, such as those caused by phase-shift or gradient-strength effects, are subtle and require careful observation for detection.

The MR appearance of CSF pulsations in the spinal canal.

We investigated the MR appearance and incidence of low-signal areas within the CSF of the spinal canal. Nonuniform areas of decreased signal intensity in intracranial CSF have been named the CSF flow-void sign (CFVS) and appear to be due to spin dephasing secondary to pulsatile CSF motion. Similar areas are seen in the spinal canal. The MR scans of 50 randomly selected patients, constituting a total of 63 spinal studies, were reviewed. There were 27 cervical, 16 thoracic, and 20 lumbar spine examinations. All patients were studied using T2-weighted and T1-weighted spin-echo pulse sequences. T2-weighted images were done with sufficiently long TE and TR to cause the CSF to appear hyperintense compared with brain and spinal cord tissue. Two patients with enlarged spinal canals and two patients with syringohydromyelia were also included to illustrate the appearance of prominent CSF pulsations. The CFVS was identified on T2-weighted scans in the cervical spinal canal in nine patients (33%), in the thoracic spinal canal in one patient (6%), and possibly in the lumbar spinal canal in two patients (10%). The CFVS was prominent in two patients with enlarged CSF spaces and was also seen in the intramedullary cavity of the patients with syringohydromyelia. The CFVS could obscure small dural lesions and, in some instances, simulate enlarged vessels. Recognition of the spinal CFVS is important to avoid the incorrect diagnosis of intraspinal lesions.

MR demonstration of altered cerebrospinal fluid flow by obstructive lesions.

We investigated the MR imaging appearance of flowing cerebrospinal fluid (CSF) in the brain in the presence of obstructive lesions of the ventricular pathways. The pulsatile movement of CSF through the ventricular system is seen as an area of low signal intensity that has been termed the CSF flow-void sign (CFVS). This is best appreciated in areas of narrowing within the ventricular system; that is, the aqueduct of Sylvius, foramen of Magendie, and interventricular foramina. MR studies of 27 patients with lesions affecting the ventricular pathways were reviewed for the presence of the CFVS. Single-echo T1-weighted and T2-weighted multisection techniques were used in all cases. The CFVS was always seen more prominently on the T2-weighted images. The presence of the CFVS indicated patency of the ventricular pathway in which it was identified. The absence of the CFVS in the presence of hydrocephalus indicated that a possible obstructive lesion was present, but it did not directly indicate the level of the obstruction. The CFVS was absent in the aqueduct of Sylvius in 13 patients with obstruction or stenosis of the aqueduct, but it was also absent in one patient with a colloid cyst of the interventricular foramina. In three patients with preoperative and postoperative MR, the CFVS was seen in the area of interest only after resection of the obstructing lesion. We concluded that the presence of the CFVS is a useful indicator of the patency of the ventricular pathway in which it is seen. The absence of the CFVS at a location in which it is normally seen may indicate the presence of an obstruction, but it must be correlated with other signs to be interpreted correctly.

Comparison of low and high sodium and potassium content in oral rehydration solutions.

PIP: Oral rehydration solutions (ORS) with low and high sodium or potassium contents were compared in 84 infants aged 3-15 months with dehydration caused by acute watery diarrhea. In randomized, double-blind trials, the ORS contained (in mmol/liter): glucose, 110; HCO3, 30; K, 10; Na, 60 (low) or 90 (high), or, in a second trial, the high Na formula plus 20 vs. 35 mEq/liter of K and extra oral water, given in the ratio of 2 bottles (240 ml) of ORS followed by 1 bottle of plain water (the 2:1 regimen). The balance technique was used to measure net absorption. Of the 84 infants, only 1 required intravenous therapy. During the first 6 hours of therapy, mean sodium absorption was significantly lower in the low Na group, and hyponatremia was more common. A few high Na group infants receiving no extra oral water had transient mild asymptomatic hypernatremia. Mean K absorption from 0-6 hours was significantly higher in the high K group, and they had no hypokalemia after oral rehydration; in contrast, 33% of the low K infants had hypokalemia. High Na ORS in the 2:1 regimen caused no electrolyte abnormalites, yielded better sodium absorption, and was usable in all age groups and for all diarrheas. High K ORS corrected K deficits better than the low K ORS. An increase in potassium concentration above that in the currently recommended ORS formula should be considered.^ieng