Diagnostic criteria for influenza B-associated Reye's syndrome: clinical vs. pathologic criteria.

Between December 15, 1973, and Jun 30, 1974, a total of 379 cases of Reye's syndrome was reported to the Center for Disease Control. One hundred forty-seven (40%) were confirmed by either autopsy or biopsy, while 232 were diagnosed by clinical and laboratory parameters. Comparisons of the epidemiologic and demographic characteristics, the hospital course, the outcome, and the laboratory abnormalities of the clinically diagnosed and the pathologically confirmed cases revealed no significant differences. In the epidemiologic setting of influenza B outbreaks, children who have the acute onset of noninflammatory encephalopathy associated with elevated serum transaminase levels, hypoprothrombinemia, and elevated blood ammonia levels should be considered to have Reye's syndrome. Further evaluation of diagnostic criteria is needed, however, for sporadically occurring, nonepidemic cases of noninflammatory encephalopathy associated with hepatic dysfunction.

Viral hepatitis in the United States, 1970-1973: an analysis of morbidity trends and the impact of HBS Ag testing on surveillance and epidemiology.

Morbidity and surveillance data on viral hepatitis cases in the United States since 1970 has revealed plateauing of case rate, continued failure to observe seasonal variation, more general geographic distribution of cases, and persistence, although at progressively lower levels, of highest rates in males 15-29 years of age. Based on results of HBS Ag testing, as much as 24 per cent of hepatitis B may be misdiagnosed by physicians and from 18 to 46 per cent of reported cases can be classified hepatitis B, thus suggesting that hepatitis B may account for up to one-half the recognized viral hepatitis in this country. HBS Ag-negative hepatitis still seems commonly acquired through close personal contact; hepatitis B patients 15-29 years of age also commonly have personal contact association. Parenteral drug abuse and transfusion of blood and blood products continue to play a role in dissemination of hepatitis B, but hepatitis B seems to account for only about one half of all reported transfusion-associated hepatitis. Case fatality rates for reported cases appear to increase with age but are not higher for HBS Ab positive patients than for negative patients.

Epidemiologic field investigations by the Centers for Disease control and Epidemic Intelligence Service, 1946-87.

The epidemiologic field investigation is an important tool used by the Centers for Disease Control (CDC) to provide assistance to State, local, and international public health agencies. The Epidemic Intelligence Service (EIS) of the CDC is an ongoing program that gives physicians and other health professionals opportunities to learn and practice epidemiology. In the period 1946-87, EIS Officers and other professional staff based at CDC headquarters participated in 2,900 epidemiologic field investigations requested by State, local, and international public health agencies. Nearly two-thirds of the investigations involved infectious disease problems, while 13 percent involved noninfectious conditions; for 21.1 percent, the etiology of the problem was unknown when the investigation was initiated. Among the specific subcategories, bacterial causes were the most common, accounting for 864 (29.8 percent) of all investigations. During this 41-year period, an increasing proportion of the field epidemiologic investigations involved public health problems of noninfectious etiology. Trends in the types of investigations done probably represent the influence of such factors as CDC's priorities, organizational structure, and budget; the size of the EIS Program; national health initiatives; and the States' needs and programs.

Recent outbreaks of lymphocytic choriomeningitis in the United States of America.

Lymphocytic choriomeningitis (LCM) has been rarely reported in the American literature since 1960. It is interesting that each of the 3 epidemics reported since then has been associated with exposure to hamsters. In 1973, 48 cases of LCM spanning the years 1971-1973 occurred at the University of Rochester Medical School associated with hamsters implanted with tumour tissues. These tissues were found to be LCM-positive, as in an earlier outbreak in 1965 at the National Institutes of Health. A nationwide outbreak of LCM occurred in late 1973 and early 1974 totalling at least 181 cases in 12 states; all were associated with pet hamsters from a single breeder in Birmingham, Alabama. He was an employee of a biological products firm whose tumour tissues were found positive for LCM and were also incriminated in the 1973 Rochester outbreak. The last outbreak occurred in a graduate school laboratory in New York State involving 7 individuals working with hamster tumours from the same Birmingham biological firm. The nationwide epidemic ended in middle April 1974 following removal of incriminated hamsters from pet shops throughout the country and voluntary cessation of distribution of hamsters from the incriminated breeder. The biological firm notified all laboratories of the possible contamination of tumours and has voluntarily stopped distribution of known positive tumours.

Paralytic poliomyelitis can be eliminated.

Since the introduction and widespread use of inactivated and oral poliovirus vaccines, there has been a continued and increasing commitment to worldwide poliomyelitis control. The eradication of poliomyelitis in certain countries, smallpox eradication worldwide, the World Health Organization's (WHO) Expanded Programme on Immunization, and advances in poliovirus vaccine production augur well for worldwide elimination within the next few decades. The success of any such program rests firmly upon scientific feasibility, intensive epidemiologic surveillance, and economic justification. The development of a variety of disease-specific control/prevention programs worldwide have improved communicable disease reporting in many countries and established health-care infrastructure as well. Equally important has been the emergence of the concept of epidemiologic surveillance. The success of poliomyelitis elimination in large parts of the world, the WHO commitment, and the tragic, visible effects of poliomyelitis are sufficiently strong arguments to persuade the countries of the world to make the necessary effort to eliminate poliomyelitis within the next generation.

Influenza surveillance in the United States 1972-1974.

Individual cases of influenza are not reported nationally to the Center for Disease Control (CDC). Other methods of surveillance, therefore, must be used to estimate the extent and impact of influenza in the country. In the past, CDC has performed telephone surveys during the respiratory season and tabulated mortality due to pneumonia and influenza from 121 cities. The telephone data vary considerably from state to state and are only a general assessment of influenza activity. Tabulation of influenza-pneumonia deaths reflects more accurately the extent and impact of influenza but suffers from a 3-4 week-lag behind the actual clinical events. To improve influenza surveillance over the past 2 years, CDC obtained weekly numbers of emergency room visits to large community hospitals, school and industrial absenteeism, numbers of specimens submitted and numbers positive for influenza isolation from laboratories throughout the United States. Surveillance was most effective in large urban areas of the US where community hospital emergency rooms function as private physicians. Where people are more likely to consult a private physician than utilize a hospital emergency room, the correlation between private physician visits and influenza was good. Furthermore, school and industrial absenteeism are not very sensitive indicators of influenza-A activity; however, school absenteeism was a good index of influenza-B activity.

Vaccine-associated poliomyelitis in the United States, 1961-1972.

Although poliovirus vaccines have led to a dramatic reduction in the incidence of poliomyelitis in the United States, there is evidence that vaccine-related cases have occurred in both vaccine recipients (recipient cases) and their contacts (contact cases) and that the incidence and epidemiologic characteristics of these cases in the 12-year period 1961-1972 have changed. Before 1965, there were 63 recipient cases compared with only 16 between 1965 and 1972. These latter cases were in younger persons and were more frequently associated with trivalent oral poliovirus vaccine (TOPV) than the former cases. Both groups were predominantly male and had intervals between immunization and onset of illness that clustered between 7 and 21 days. Only three contact cases were recognized before 1965, compared with 39 cases in 1965-1972. The increase was in both children and adults. Unlike recipient cases, contact cases were almost as frequent in females as in males. Evidence that the contact cases were vaccine-related included the apparent clustering between 20 and 29 days of the intervals from vaccine administration to onset of illness and the significantly increased frequency of longer intervals for contact cases in non-household members compared with contact cases in household members. The decrease in recipient cases and the increase in contact cases in 1965-1972 compared with the previous 3-year period are explained by the general curtailing of routine vaccination of adults after 1964, a switch from monovalent oral polio vaccine to TOPV, improved recognition of contact cases and a shift in emphasis from mass vaccination campaigns and communitywide programs to routine vaccination of infants.

The Russian flu. Its history and implications for this year's influenza season.

From November 1977 through mid-January 1978 the population younger than 25 years in the Union of Soviet Socialist Republics experienced a widespread epidemic of mild influenza (Russian flu) caused by an H1N1 virus similar to the virus that circulated worldwide during the early 1950s. Outbreaks of Russian flu occurred in school populations and military recruits in the United States starting in mid-January. Many other countries reported outbreaks of H1N1 virus in the winter of 1978. Predictions of influenza activity are always hazardous, but most experts believe that the Russian flu may occur again in the fall and winter of 1978. Other type A and B strains may also circulate; therefore, a trivalent vaccine containing A/USSR, A/Texas, and B/Hong Kong virus strains will be available. It is recommended that the chronically ill and those 65 years and older be the target populations for annual vaccination.

Hemodialysis-associated hepatitis: report of an epidemic with further evidence on mechanisms of transmission.

In the period January-September 1974, 50 cases of hepatitis B infection occurred among a nephrology center's hemodialysis patients and staff. The in-center patient population had an attack rate of 96%. Epidemiologic analysis of risk factors for patients revealed an association between the receipt of intravenous medication and the subsequent development of hepatitis, suggesting that parenteral inoculation was a mode of spread among patients (p equals .008). Nineteen per cent of the staff contracted hepatitis, and all of these personnel had had close contact with patients (p equals .005). The prevalence of hepatitis B infection in staff was related to the failure to use gloves (p less than .01), and accidental needle puncture was associated with the development of clinical hepatitis. These data suggested that disease was transmitted to staff by contact with contaminated blood or close personal contact with patients. Additional data showed that the presence of endogenous antibody protected both patients and staff from antigenemia (p equals .002). These data support the hypothesis that contact with blood is the primary mechanism of spread of hepatitis B in dialysis units, and suggest that, as preventive measures, gloves should be used and antibody-positive staff should dialyze antigen-positive patients.

Clinical aspects of human Venezuelan equine encephalitis in Texas.

The Venezuelan equine encephalitis epidemic which occurred in Texas in 1971 produced a wide range of predominantly mild clinical symptoms. This epidemic, which peaked on 13-14 July, was most intensely felt in the far-south counties of Cameron and Hidalgo. In all, 88 laboratory-confirmed human cases were reported to the U.S. Center for Disease Control by the Texas State Department of Health. The ratio of male to female cases was about two to one. An attack of 20.8 cases per 100,000, observed in both the 20-29 and 30-39 age groups, was higher than attack rates experienced by other age groups and by the population at large. Together, Cameron and Hidalgo counties experienced a much higher overall attack rate (21.7 cases por 100,000) than did affected counties in the Corpus Christi area (4.9 cases per 100,000). Knowledge about when various patients were first exposed points to an incubation period ranging from 27.5 hours to four days. In those 79 cases for which clinical data were available, the most common clinical manifestations were found to be fever, severe headache, myalgia, and chills. Evidence of mild to moderate central nervous system involvement was found in 10 out of 25 children and young people under 17 years of age, and in six out of 54 adults. Two children still had residual paralysis six weeks after onset of illness, but by 10 months these sequelae had disappeared. Seven of the 54 adults, however, still complained of tiring easily a year after onset of illness. Leukopenia, as demonstrated by a count of less rhan 4,500 white blood cells per cubic millimeter, was observed in 75 per cent of the patients examined.

HBs-Ag-negative hepatitis in a hemodialysis unit: relation to Epstein-Barr virus.

Eleven of 40 patients in a hemodialysis unit had clinical or biochemical evidence of hepatitis during a five-week period. The clinical disease was mild, being limited solely to dialysis patients. Epidemiologic investigation indicated that the incubation period was between 17 and 35 days and that 10 of 11 patients had been exposed to a single venous-pressure monitor before onset. Dried blood and evidence of blood reflux up the venous-pressure gauge suggested that cross-contamination of the blood of successive patients probably resulted in transmission of disease. No association with the hepatitis B surface antigen or anti-hepatitis B antibody was demonstrated, but 10 of the 11 patients with elevated transaminase levels had evidence of recent exposure, to Epstein-Barr virus as manifested either by Ox-cell hemolysin titers or rises in titers to viral capsid antigen.

Pontiac fever. An epidemic of unknown etiology in a health department: I. Clinical and epidemiologic aspects.

In July 1968, an explosive epidemic of acute febrile illness occurred at a county health department facility in Pontiac, Michigan. Illness characterized principally by fever, headache, myalgia, and malaise affected at least 144 persons, including 95 of 100 persons employed in the health department building. The mean incubation period was approximately 36 hours. Illness was self-limited, generally lasting from two to five days. Secondary cases did not occur in family contacts and second attacks did not consistently follow re-exposure in the building. A defective air-conditioning system was implicated as the source and mechanism of spread of the causative factor. However, extensive laboratory and environmental investigations failed to identify the etiologic agent. Since these investigations a bacterium similar to or identical with the agent responsible for Legionnaires' Disease has been isolated from guinea pigs exposed to the Pontiac health department building in 1968 as well as from guinea pigs exposed to water from the evaporative condenser. Paired sera from 32 cases of Pontiac Fever showed seroconversion or diagnostic rises in antibody titers to this bacterium.

Transmission of hepatitis B associated with hemodialysis: role of malfunction (blood leaks) in dialysis machines.

In the first 10 months of 1974, 26 of 60 susceptible patients in a commercial hemodialysis unit developed asymptomatic infection with hepatitis B virus; 17 (65%) of the 26 cases occurred in 14 weeks from July to October. In a case-control study, 15 of 16 cases for whom records were available were found to be associated with malfunctions of dialysis machines (primarily leaks or ruptures in dialysis membranes) that had occurred before patients converted to hepatitis B surface antigen (HBs Ag) positivity. In comparison, 17 of 34 controls were associated with machine malfunctions (P less than 0.01). In addition, the mean number of malfunctions in machines per patient was significantly greater for cases of infection (2.25 +/- 1.34) than for controls (1.06 +/- 1.39) (P less than 0.01). Furthermore, a direct correlation was demonstrated between an increase in blood leaks in machines used with susceptible patients and subsequent increases in cases of hepatitis for the various beds in the unit (r=0.994, P less than 0.0001). The mean period from the last blood leak to HBs Ag seroconversion was 67 days. Six of the 36 blood leaks associated with cases of infection occurred less than 6 hr after leaks in the contaminated area, whereas only one of 36 leaks associated with controls demonstrated this relationship (P less than 0.05). These data suggest that the conversion to HBs Ag positivity was linked to the occurrence of machine malfunctions (blood leaks) and that events which occurred during these episodes caused the spread of infection.