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Rabies Exposure - Continued

mens. News media events that show people playing with bats may not imply any danger; however, the national news media attention given this incident was beneficial in educating the public to potential risks. Locally, it resulted in the identification of an additional group of children in Corpus Christi that had played with dead bats and required rabies prophylaxis.

The risk to most of these children would appear to be minimal-nonbite exposure to animals already dead, probably for several hours. Exposure, if it occurred, would seem most likely through bat saliva in direct contact with children's oral mucous membranes when they mouthed the bats and/or by salivary contamination of fresh scratches and which, in this case, could have been made by the bats' teeth and claws during play. Prevention of episodes such as this are probably impossible, but proper education of the public to the health risks should reduce their occurrence.

Errata: Vol. 33, No. 25

p. 353. In the article, "Oral Contraceptive Use and the Risk of Breast Cancer in Young Women," the 95% confidence limits in Table 1 are incorrect (although the odds ratios are correct). The correct confidence limits are (reading down): (REF); (0.8, 1.3); (0.8, 1.5); (0.5, 1.3); (0.4, 2.0). Also, the second-to-last sentence of the Editorial Note on page 354 should read: Results were presented in 1983 (1) from the first 6 months of data collected.

Vol. 33, No. 24

p. 339. In the article, "Human Arboviral Encephalitis-United States, 1983," the last sentence of the third paragraph under St. Louis encephalitis should read: "The increased number of cases among adults may reflect a decline in endemic transmission with age during the past 30 years, resulting in an increase in susceptibility."

Director, Centers for Disease Control
James O. Mason, M.D., Dr.P.H.

Director, Epidemiology Program Office
Carl W. Tyler, Jr., M.D.

Editor

Michael B. Gregg, M.D. Assistant Editor

Karen L. Foster, M.A.

✩U.S. Government Printing Office: 1984-746-149/10002 Region IV

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MMWR

MORBIDITY AND MORTALITY WEEKLY REPORT

Epidemiologic Notes and Reports

377 Antibodies to a Retrovirus Etiologically
Associated with Acquired Immunodeficiency
Syndrome (AIDS) in Populations with
Increased Incidences of the Syndrome
379 Injuries at a Water Slide-Washington
387 Salmonellosis Associated with Cheese

Consumption-Canada

388 Enterovirus Surveillance-United States,

1984

388 Imported Malaria among Travelers-United States

390 Availability of CDC-NIH Biosafety Manual

Antibodies to a Retrovirus Etiologically Associated
with Acquired Immunodeficiency Syndrome (AIDS)
in Populations with Increased Incidences of the Syndrome

Evidence implicates a retrovirus as the etiologic agent of acquired immunodeficiency syndrome (AIDS). Two prototype isolates have been described. One was isolated from the lymph node cells of a homosexual man with unexplained generalized lymphadenopathy, a syndrome associated with AIDS, and was termed lymphadenopathy-associated virus (LAV) (1). A morphologically similar T-lymphotropic retrovirus (HTLV-III) was isolated from lymphocytes of 26 (36%) of 72 patients with AIDS and from 18 (86%) of 21 patients with conditions thought to be related to AIDS (2). The isolation of retroviruses antigenically identical to LAV from a blood donor-recipient pair, each of whom developed AIDS, provides further evidence that this virus is the etiologic agent of AIDS and may be transmitted through blood transfusion (3). Although direct comparative results have not been published, HTLV-III and LAV are likely to be the same virus because: they have the same appearance by electron microscopy; they are both lymphotropic and cytopathic for OKT-4 cells; isolates from American AIDS patients, when compared, were immunologically indistinguishable from LAV (3); serologic tests of a large number of specimens from patients with AIDS or related conditions show similar results when either of the prototype viruses is used as antigen (4); and preliminary results suggest that LAV and HTLV-III are at least highly related based on competitive radioimmunoassay of their core proteins (5).

Three basic serologic procedures are currently described for detection of antibody to HTLV-III/LAV: an enzyme-linked immunosorbent assay (ELISA) to whole disrupted virus (6-8); a radioimmunoprecipitation assay (RIPA) to the presumed major core protein (called p25) of LAV (9); and assay of antibody to major viral antigens by the Western blot technique (10, 11). Sera from several high-risk populations are being tested by these techniques by the National Cancer Institute, the Institut Pasteur, and CDC, with the support of numerous collaborators. The objectives of these investigations are to determine the frequency of exposure to HTLV-III/LAV and to correlate seropositivity with current infection, clinical signs and symptoms, and prognosis.

Preliminary data suggest that serologic evidence of exposure to HTLV-III/LAV may be common in certain populations at increased risk for AIDS. Antibody to HTLV-III was detected by ELISA in sera from six (35%) of 17 American homosexual men without symptoms of AIDS (6). Sera from eight (18%) of 44 homosexual men without lymphadenopathy attending a venereal disease clinic in Paris had antibody detected by ELISA to LAV (7). Antibody prevalence to LAV (RIPA) has increased from 1% (1/100) in 1978 to 25% (12/48) in 1980 and 65% (140/215) in 1984 among samples of sera from homosexual men attending a sexually

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES / PUBLIC HEALTH SERVICE

AIDS - Continued transmitted diseases clinic in San Francisco (12). Antibody prevalence among the above men tested in 1984 who had no symptoms or clinical signs of AIDS or related conditions was 55% (69/126) (12). In New York City, where the AIDS cases among intravenous (IV) drug users are concentrated, 87% (75/86) of recent heavy IV drug users without AIDS had antibody to LAV by ELISA, while over 58% (50/86) of the same group had antibody to LAV detected by RIPA (13). In contrast, fewer than 10% of 35 methadone patients from New York City had antibody to LAV detected by RIPA. All of these latter patients had been in treatment at least 3 years with greatly reduced IV drug usage (14). Seventy-two percent (18/25) of asymptomatic persons with hemophilia A in a home-care treatment program demonstrated antibody to LAV antigens utilizing the Western blot technique (11). All had used factor VIII concentrates from 1980 to 1982.

Reported by DC Des Jarlais, PhD, New York State Div of Substance Abuse Svcs, M Marmor, PhD, H Cohen, MPH, New York University Medical Center, S Yancovitz, MD, J Garber, Beth Israel Medical Center, S Friedman, PhD, Narcotic and Drug Research, MJ Kreek, MD, A Miescher, MD, E Khuri, MD, Rockefeller University, New York City, SM Friedman, MD, New York City Dept of Health, R Rothenberg, MD, State Epidemiologist, New York State Dept of Health; D Echenberg, MD, P O'Malley, E Braff, MD, San Francisco City/County Health Dept, J Chin, MD, State Epidemiologist, California Dept of Health Svcs; P Burtenol, MD, Hemophilia of Georgia, Atlanta, RK Sikes, DVM, State Epidemiologist, Georgia Dept of Human Resources; Div of Viral Diseases, Div of Host Factors, AIDS Activity, Center for Infectious Diseases, CDC.

Editorial Note: The high prevalence of antibody to HTLV-III/LAV among these groups and the increasing prevalence among homosexual men in San Francisco add further support to HTLV-III/LAV being the etiologic agent of AIDS. They further demonstrate that exposure to the virus is much more common than AIDS itself among populations with increased incidences of the disease. If AIDS follows the pattern of many other infectious diseases, host response to infection would be expected to range from subclinical to severe. Milder disease states for AIDS have been suspected, since the reported frequency of lymphadenopathy and immunologic abnormalities, conditions associated with AIDS, has also been high in these groups. These data, based on limited samples of high-risk groups, suggest the spectrum of response to infection with HTLV-III/LAV may be wide.

These serologic tests are sufficiently sensitive and specific to be of value in estimating the frequency of infection with HTLV-III/LAV in certain populations and for providing important information about the natural history of the disease in such groups. Less clear are the implications of a positive test result for an individual. For some, the result may be a false positive caused by infection with an antigenically related virus or nonspecific test factors. The determination of the frequency and cause of falsely positive tests is essential for proper interpretation of test results, but remains to be established, particularly in populations, such as blood donors who belong to no known AIDS risk groups, where the prevalence of true infection with HTLVIII/LAV is expected to be very low.

A positive test for most individuals in populations at greater risk of acquiring AIDS will probably mean that the individual has been infected at some time with HTLV-III/LAV. Whether the person is currently infected or immune is not known, based on the serologic test alone-HTLV-III/LAV has been isolated in both the presence and absence of antibody-but the frequency of virus in antibody-positive persons is yet to be determined. For seropositive individuals with mild or no signs of disease, including those in whom the virus can be demonstrated, the prognosis remains uncertain. The incubation period for the life-threatening manifestations of AIDS may range from 1 year to more than 4 years (15).

Carefully planned and executed studies will be required to resolve these issues, and to clarify remaining questions about the natural history of AIDS and risk factors for transmission of the virus.

AIDS-Continued

Until the usefulness of positive and negative serologic tests is fully established, all individuals in populations with increased incidences of AIDS, as well as those outside such groups with positive tests, should comply with the March 1983 Public Health Service recommendations for the prevention of AIDS to minimize the transmission of the syndrome (16). Abstention from IV drug usage and reduction of needle-sharing and other use of contaminated needles by IV drug users should also be effective in preventing transmission of the virus and of AIDS. There remains no evidence of transmission of AIDS through casual contact. Prevention measures should stress that transmission has been only through intimate sexual contact, sharing of contaminated needles, or, less frequently, through transfusion of blood or blood products.

References

1. Barre-Sinoussi F, Chermann JC, Rey F, et al. Isolation of a T-lymphotropic retrovirus from a patient at risk for acquired immune deficiency syndrome (AIDS). Science 1983;220:868-71.

2. Gallo RC, Salahuddin SZ, Popovic M, et al. Frequent detection and isolation of cytopathic retroviruses (HTLV-III) from patients with AIDS and at risk for AIDS. Science 1984;224:500-3.

3. Feorino DM, Kalyanaraman VS, Haverkos HW, et al. Lymphadenopathy associated virus infection of a blood donor-recipient pair with acquired immunodeficiency syndrome. Science 1984;225:69-72. 4. Kalyanaraman VS, Cabradilla CD, Jaffe HW, et al. Personal communication.

5. Sarngadharan MG, Montagnier L, Chermann JC, Rey F, Popovic M, Gallo RC. Personal communication.

6. Saxinger C, Gallo RC. Application of the indirect enzyme-linked immunosorbent assay microtest to the detection and surveillance of human T cell leukemia-lymphoma virus. Lab Invest 1983;49: 371-77.

7. Sarngadharan MG, Popovic M, Bruch L, et al. Antibodies reactive with human T-lymphotropic retroviruses (HTLV-III) in the serum of patients with AIDS. Science 1984;224:506-8.

8. Brun-Vezinet F, Rouzioux C, Barre-Sinoussi F, et al. Detection of IgG antibodies to lymphadenopathy-associated virus in patients with AIDS or lymphadenopathy syndrome. Lancet 1984;1:1253-6.

9. Kalyanaraman VS, Cabradilla CD, Getchell JP, et al. Antibodies to the core protein of the human retrovirus LAV in patients with acquired immunodeficiency syndrome and lymphadenopathy syndrome. Science (in press).

10. Tsang VCW, Peralta JM, Simons AR. The enzyme-linked immunoelectro-transfer blot techniques (EITB) for studying the specificities of antigens and antibodies separated by gel electrophoresis. Methods Enzymol 1983;92:377-91.

11. Ramsey RB, Palmer EL, McDougal JS, et al. Unpublished data. 12. Francis DP, Darrow WW, O'Malley P, et al. Unpublished data.

13. Spira TJ, Des Jarlais DC, Marmor MM, et al. Unpublished data.

14. Kreek MJ, Des Jarlais DC, Kalyanaraman VS, et al. Personal communication.

15. Curran JW, Lawrence DN, Jaffe HW, et al. Acquired immunodefiency syndrome (AIDS) associated with transfusions. N Engl J Med 1984;310:69-75.

16. CDC. Prevention of acquired immunodeficiency syndrome (AIDS): report of inter-agency recommendations. MMWR 1983;32:101-3.

Epidemiologic Notes and Reports

Injuries at a Water Slide- Washington

On July 12, 1983, a new outdoor water slide consisting of two fiberglass tubes 4 feet in diameter and 360 feet in length opened in Washington State. Sliders climbed 55 vertical feet to the entrance, where they jumped into a current of water and rode it through either tube, negotiating two 360-degree turns and two 45-degree drops before exiting into a splash pool.

Injuries - Continued

From July 13 to August 31, 65 persons injured at this amusement ride sought medical care in local physicians' offices and emergency rooms and were reported to the County Emergency Medical Service. The slide operators reported that 178 patrons sought first aid at their facility, of whom 10 (6%) were transported to a hospital. The rate of injury recorded by the slide operators was 8.1 per 10,000 rides sold, and the rate of medically treated injuries was 3.0/10,000.

The 65 medically treated sliders ranged in age from 8 years to 45 years. Age was unknown in one case. About equal numbers were aged 5-14 years, 15-24 years, and 25 years or older (Table 1); 42 (65%) were female. Injuries included fractures, concussions, bruises and abrasions, and sprains and strains (Table 1). Most concussions, skull and spinal fractures, lacerations, and "other injuries" occurred among females, while most sprains, strains, and "other fractures" affected males. For all injuries except concussions, the majority of persons were aged 15 years or older. All fractures occurred among persons 15 years of age or older. Of the nine spinal fractures, eight were lumbar compression fractures and one was a fracture of the coccyx. The "other fractures" were of the ribs in one case and of the humerus in the other. The sprains and strains were primarily back injuries. Of the 18 lacerations, 12 (67%) required

sutures.

TABLE 1. Distribution of 65 water slide injury cases, by type of injury and age and sex of victim Washington, 1983

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