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In 1986 the World Health Organization targeted dracunculiasis (Guinea-worm disease), which seriously impairs socioeconomic development in 16 African countries, India, Pakistan, and Yemen, to be eradicated globally. The target date for eradication by the end of 1995 was established in 1991. Pakistan eradicated dracunculiasis from the country in October, 1993, after a national campaign which began in 1987 with a nationwide village-by-village search for cases. The infection, which is transmitted by drinking water from ponds containing infected water fleas, was eradicated by using health education, cloth filters, and the cyclopsicide, temephos; and in the later stages, by case containment. Methods pioneered in Pakistan's National Guinea Worm Eradication Program are now being applied in remaining endemic countries.

To document patterns of intestinal parasitism in the United States, we analyzed results of 216,275 stool specimens examined by the state diagnostic laboratories in 1987; parasites were found in 20.0%. Percentages were highest for protozoans: Giardia lamblia (7.2%), Entamoeba coli and Endolimax nana (4.2% each), Blastocystis hominis (2.6%), and Entamoeba histolytica (0.9%). The most commonly identified helminths were nematodes: hookworm (1.5%), Trichuris trichiura (1.2%), and Ascaris lumbricoides (0.8%). Identifications of G. lamblia increased broadly from the 4.0% average found in 1979, with 40 states reporting increases and seven reporting decreases. Seasonally, Giardia identifications increased in the summer and fall, especially in the Midwest. Nine states reported hookworms in more than 2% of specimens; none were states with indigenous transmission. We analyzed similar, but abbreviated, data for 1991; parasites were found in 19.7% of the 178,786 specimens and Giardia was found in 5.6%. States reporting percentages of Giardia identification in the highest quartile for both 1987 and 1991 were located in the Midwest or in the Northwest. Cryptosporidium was identified in both the 1987 and 1991 surveys; it had not been identified in a previous survey. For each year, Cryptosporidium was reported from 25 states across the country (for both years in 17 states). We conclude that intestinal parasitism should not be overlooked as a cause of gastrointestinal illness in the United States and that the prevalence of Giardia may be increasing.

Cases of acute encephalitis reported to the CDC are divided into five groups: arboviral (8% of the 1965 to 1974 total), enteroviral (2%), post-infection (25%), encephalitis due to other known agents (3%), and encephalitis of indeterminate etiology (62%). With increased use of live virus vaccines against measles, mumps, and rubella, postinfection encephalitis has decreased, and SLE had become one of the most common preventable encephalitides in the United States. In 1975 SLE virus caused at least 1,791 cases of encephalitis, 42% of the reported total. In addition, the age distribution of persons with encephalitis of indeterminate etiology suggests that SLE virus may be an important contributor to that caegory during the summer months. The warm-weather transmission cycle of the SLE virus is well established. The reservoir is birds. The principal vector is the peridomestic C. pipiens mosquito in the Midwest and South and the rural C. tarsalis in the West. Man is an incidental and dead-end host. The winter reservoir is unknown. Human illness occurs in the summer. Asymptomatic human infections are about 200 times more common than symptomatic infections. Clinical attack rates and severity of illness increase with age. Case-fatality ratios of 35 to 38% have been reported for persons 60 years of age and older. For unknown reasons, SLE virus causes periodic major epidemics. The epidemics are more noticeable and better studied in major cities, but they probably affect rural areas as well. SLE is more common in areas of the country with warm climates. Epidemics in the North, when they occur, begin later but are of the same duration as epidemics in the South. Presumably, large epidemics of SLE can be prevented by mosquito control programs. Cumbersome and possibly insensitive diagnostic techniques impair our evaluation and understanding of SLE and other encephalitides. Insufficient information about the factors causing or preceding SLE epidemics impedes successful preventive measures. The use of emergency mosquito control programs after an epidemic has started has not been shown to reduce the number of human cases.

When increases in influenzalike illnesses were first detected during the 1984 to 1985 and 1985 to 1986 influenza seasons, throat swab specimens were mailed by physicians across the United States to one hospital laboratory, and each specimen was inoculated into a single tube of cell culture. Of 165 specimens, 52 (32%) were positive for influenza A or B virus within 3 days of receipt when tested by fluorescence microscopy, permitting positive results to be received by the physicians within 1 week on the average. Approximate direct cost was $16 per specimen.

In June 1977 an outbreak of acute gastroenteritis affected 103 students and teachers at an elementary school in Ohio. The illness typically lasted 24 hours or less and was characterized by vomiting (86%) and cramping (70%), but more than half of the persons involved also reported having nausea, diarrhea, and headache. Similar illness frequently followed in household members (29%) of families with primary cases. Investigation revealed that 70% of the children and teachers who swam in a pool at an all day outing June 1 (4 classrooms) and 55% of those who swam during a similar outing June 2 (2 classrooms) had the onset of acute illness from 12--48 hours later. None of the children who attended the outings but did not swim had a similar illness. The evidence suggested that the primary outbreak was caused by contaminated water in the pool and that person-to-person spread of illness followed. Results of a microbiologic study of pool water were negative for bacterial and viral pathogens. Throat washings, stool specimens, and paired blood samples studied for evidence of pathogens were negative initially, but subsequent serologic studies suggested that infection by Norwalk virus was the cause of the outbreak. The pool chlorinator which was inadvertently unconnected at the time of the school visits was reconnected and an underground leak in the water supply pipes was corrected. No more cases were reported after the pool was drained, cleaned, and reopened.

Data were examined on 965 persons treated in six States (Delaware, Florida, Georgia, Illinois, North Dakota, and South Carolina) and New York City in 1972 for possible rabies exposure. Males 10-19 years were found to be the group at greatest risk, and exposures occurred most frequently during the warm months. Dogs, other domestic animals, and wildlife were about equally responsible for human exposures in the six States, but 99% of the exposures in New York City involved dogs. Antirabies postexposure prophylaxis varied markedly among reporting areas and frequently did not follow current recommendations. The mean delay in initiation of treatment after exposure was 4 1/2 days. The mean number of doses of vaccine for treatment was 12; only 10% of the persons treated received antirabies serum.

Epidemics of dengue-like illness occurred in the Seychelles from December 1976 to April 1977 and from December 1978 to January 1979. Dengue 2 virus was isolated from individuals who had been in the Seychelles in 1977. From February to April 1979, sera were collected from outpatients in Mahé, Seychelles, who had not previously been hospitalized with a dengue-like illness. Results of neutralization tests with these sera indicated that prevalence rates for the four dengue viruses were between 81% and 91.8% and that dengue 2 was the most probable etiological agent in the epidemics. In addition, antibodies to chikungunya (8.7%) and Sindbis (7.4%) viruses were found, providing, for the first time, evidence of the presence of these two alphaviruses in the Seychelles.

From 1971 through 1973 629 reported cases of rabies in dogs, concentrated in the Appalachian area, upper Mississippi drainage, Texas, and Louisiana, were reported in the US. States bordering the Atlantic and Pacific oceans had fewer cases. There was a recurring seasonal pattern of cases with a peak in March and April and a low point in August and September. Most of the cases involved transmission from wildlife vectors rather than dog-to-dog transmission. Most of the dogs were owned (87%), unvaccinated (87-90%), and adult (72%); most demonstrated unaggressive behavior (74%) and had exposed humans (75%). A history of vaccination was reported for 60 of the dogs. There were 21 cases of apparent vaccine failure involving all the types of vaccines in use during the study period. The attack rate for unvaccinated dogs was estimated to be 14 to 19 times higher than for vaccinated dogs. Since canine rabies in the United States is predominantly a problem in owned, invaccinated pets, vaccination and licensing of dogs should be mandatory. Surveillance should be continued to ensure that any resumption of dog-to-dog transmission will be rapidly detected and to monitor efficacy of vaccines in current use.

Active surveillance for La Crosse infection from 1977 to 1979 revealed 12 laboratory documented cases in children from the Cherokee reservation and nearby areas of western North Carolina. The annual rate of hospitalization with La Crosse virus was isolated from two of 34 pools of male and one of 34 pools of female Aedes triseriatus mosquitoes reared from larvae collected around the residences of reservation children who had been hospitalized with encephalitis. The occurrence of the recent cases, the history of cases in 1964 and 1965, and the demonstration of antibodies to La Crosse virus in sera from second grade children collected in 1968 (2%), in 1978 (4.5%), and in high school students in 1979 (11.3%), indicate that La Crosse has persisted in the Cherokee area for at least 15 years. La Crosse infection is infrequently reported from the southeast, but this may reflect inactive surveillance. More frequent testing would reveal whether La Crosse is a significant health problem in other areas of the southeast.

From 8 August through 5 December 1977, 110 laboratory-documented cases (78 confirmed, 32 presumptive) of St. Louis encephalitis (SLE) occurred in 20 counties throughout central-south Florida. Most cases were initially identified through an active surveillance system involving repeated contact of hospital infection control officers. This outbreak had three characteristics that are unusual for SLE epidemics in the eastern United States: it lacked an urban focus, a disproportionate number of cases affected young males, and the epidemic period extended into December. There was no significant difference between attack rates for blacks and whites. Males were significantly more often affected than females. Because of the time required for laboratory confirmation of cases, most outbreak control measures were initiated after the outbreak was declining. Reporting of clinically suspected SLE cases to initiate epidemic mosquito control should improve the timeliness of control measures in future outbreaks.

In February 1982, a four-year-old Nevada girl with acute lymphoblastic leukemia in remission was hospitalized with fulminant pneumonia and died eight days later at a hospital in California. An influenza virus was the only pathogen detected, and was present in both antemortem and postmortem specimens. The virus was closely related antigenically to A/New Jersey/8/76 (H1N1) and had a genome very similar to a contemporary enzootic swine influenza virus. The patient had had no known contact with swine, and the source of infection could not be determined. Only five possible secondary cases could be detected by retrospective investigation of 62 contacts, and there was no evidence of spread to the general community. Swine influenza viruses circulate among pigs in the United States annually, and it is likely that sporadic transmissions to humans will continue to be detected. Nevertheless, person-to-person spread under these circumstances appears to be limited.

The geographic distribution of enzootic rabies in raccoons is currently limited to Florida and Georgia. The enzootic area has steadily expanded northward into Georgia during the 1960's. An epizootic in a population of raccoons closely associated with the human residents of a small, off-shore island was investigated. Forty-seven raccoons from the island were confirmed rabies positive by the State Laboratory from January 22 to May 20, 1969. About 10 percent of the raccoons trapped during the peak of the epizootic were positive and all of these had high titers of virus in their salivary glands but were asymptomatic in behavior. Human exposure typically resulted from close approach to a "sick" raccoon. Similar outbreaks may occur elsewhere when humans live in close contact with a semi-domesticated raccoon population. Rabies vaccination of raccoons should be considered as an alternative to population reduction in such situations.