Genetic variability of HIV type 1 in Honduras.

PIP: While Honduras is home to only 15% of Central America's population, it has 60% of the region's AIDS cases. There have been 4973 reported cases of full-blown AIDS in the country and the Health Ministry reports that more than 8000 Hondurans have been infected with HIV since the first Honduran case was diagnosed in 1985. 995 people with AIDS have since died. The authors conducted an investigation to determine which HIV-1 subtype is present in Honduras and the degree of genetic variation among HIV-1 strains by analyzing viral nucleotide sequences from the envelope region of HIV-1 isolates obtained from the two most affected regions of the country. They determined the predominant HIV-1 subtype among 27 HIV-1-infected patients attending sexually transmitted disease clinics in San Pedro Sula and Tegucigalpa by sequencing and analyzing the C2V3 regions of the envelope glycoprotein gp 120. Genomic DNA was isolated from patients' peripheral blood mononuclear cells. Phylogenetic analysis determined that all 27 Honduran sequences clustered with known subtype B sequences.^ieng

Field evaluation of rapid HIV serologic tests for screening and confirming HIV-1 infection in Honduras.

OBJECTIVE: To determine the ability of simple, rapid tests to identify HIV-1 antibody-positive specimens in field settings using the World Health Organization's (WHO) alternative testing strategies. DESIGN: Three-phase evaluation of simple, rapid assays using banked specimens and prospectively collected serum specimens at regional hospitals and rural clinics. METHODS: Seven test (Retrocell, Genie, HIVCHEK, SUDS HIV-1, Testpack, Serodia HIV-1, and HIV-1/2 RTD) were evaluated and results compared with standard enzyme immunoassay (EIA) and Western blot results (phase 1). Further evaluation consisted of prospective testing of routine specimens at regional (phase 2; n = 900) and rural, peripheral laboratories (phase 3; n = 1266) throughout Honduras with selected assays. RESULTS: Sensitivity and specificity were calculated for each assay and combination of assays for each phase to evaluate the effectiveness of the WHO alternative testing strategies. All tests in all phases were > 99% sensitive after correcting for technical errors, with two exceptions (SUDS, phase 1; HIVCHEK, phase 3). In phase 3, where the testing algorithm was diagnostic, several combinations of assays were 100% sensitive and specific using WHO strategy II or III. For the Honduras Ministry of Health, the combination of Retrocell and Genie was found to be equally sensitive, more specific (no indeterminate results), and less expensive than EIA/Western blot. CONCLUSION: Combinations of rapid, simple HIV antibody assays provide sensitivity and specificity performance comparable to EIA/Western blot. Application of these combinations in the WHO alternative testing strategies provides an inexpensive and effective method of determining HIV status. Assay combinations using these strategies can be easily performed in small, rural laboratories and have been implemented in routine HIV screening in Honduras.

PIP: In 1992, the World Health Organization (WHO) introduced 3 HIV testing algorithms designed to provide rapid, accurate results equivalent to those obtained by enzyme immunoassay (EIA) and Western blot but at reduced costs. The capability of the WHO strategy to identify HIV-1 antibodies in field settings was evaluated at regional hospitals and rural clinics in Honduras. In the study's first phase, the results of 7 tests (Retrocell, Genie, HIVCHEK, SUDS HIV-1, Testpack, Serodia HIV-1, and HIV-1/2 RTD) were compared with results for 600 sera previously tested by EIA and Western blot. Phase 2 entailed prospective testing of 900 routine specimens at regional laboratories, while phase 3 screened 1266 specimens at rural, peripheral laboratories. In the first phase of the analysis, 5 assays had a sensitivity of 100%; the remaining 2 were 99.7% and 99.3% sensitive and specificities ranged from 92.8 to 100%. In field settings, sensitivities ranged from 96.4 to 99.3%. Moreover, in the third phase, several combinations of tests were 100% sensitive or specific when the WHO strategy of basing the choice of assay on the purpose of the screening (seroprevalence studies, screening of blood, or patient diagnosis) was employed. The combination of Retrocell and Genie was found to be equally sensitive, more specific, and less expensive than EIA or Western blot.

Epidemic dermatitis due to contact with a moth in Cozumel, Mexico.

In early December 1989, an outbreak that was initially thought to be scabies was investigated among employees of tourist hotels in Cozumel, Mexico. Of 417 employees interviewed, only 19 (4.6%) met a case definition for scabies dermatitis, while 91 (21.8%) reported a nonspecific dermatitis of less than one-week's duration. Persons with nonspecific dermatitis related the onset of their dermatitis to skin contact with a moth that had been present in large numbers in November. At the time of the initial investigation in December, there were no active cases of dermatitis and the moth was no longer present. During early January 1990, numerous cases of dermatitis again began to be reported. Using a case definition for nonspecific dermatitis, a survey of Cozumel's resident population showed an attack rate of 12.1%. A case-control study revealed the only significant risk factor to be skin contact with the suspect moth (P less than 0.01), which had returned in large numbers. Six health workers volunteered to have the moth rubbed on their skin; within 5 min, five of six developed an intense pruritus followed by an erythematous rash. The moth was classified as Hylesia alinda Druce. This species has nettling hairs on its abdomen that excrete a histamine-like substance. Although this moth is normally present in small numbers in Cozumel, the passage of hurricane Gilbert killed most of its natural predators (wasps and bees), allowing its population to overgrow. No control measures were undertaken because the moth's natural predators returned that spring and dramatically reduced the moth population. No further outbreaks of dermatitis occurred.

Protective effect of antibiotics on mortality risk from acute respiratory infections in Mexican children.

A case-control study of mortality from acute respiratory infections (ARI) among children under five years of age was conducted in Naucalpan, an urban-suburban area of Mexico City, and in rural localities of Tlaxcala, Mexico. The study found that ARI deaths tended to occur in the poorest neighborhoods; 78% of the deceased study subjects were infants under six months old; and 68% of the deaths occurred at home. Comparison of the data for cases (fatalities) and control children who had severe ARI but recovered showed that failure to receive antibiotics was associated with death (odds ratio 28.5, 95% confidence interval 2.1-393.4). This antibiotic effect was controlled for numerous potentially confounding factors. It is evident that antibiotics had a much greater effect in the early days of the illness than later on. In general, the findings strongly support PAHO/WHO primary health care strategies--including such strategies as standardized management of severe ARI cases--that seek to reduce childhood ARI mortality.

An outbreak of Cryptosporidium diarrhea in a pediatric hospital.

PIP: Physicians investigated a nosocomial diarrhea outbreak among 11 2 year old undernourished children in the nutrition service of the pediatric teaching hospital, Hospital Infantile, in Mexico City, Mexico in April 1988. Health practitioners took at least 2 stool samples from each ill child to be analyzed for Cryptosporidium oocysts. The attack rate stood st 82%. The hospital admitted a malnourished child with chronic diarrhea and pneumonia on March 22. Laboratory tests revealed that he had many Cryptosporidium oocysts and was positive for HIV. Hospital staff did not isolate him. He died on May 9 of Escherichia coli and Candida septicemia. The outbreak ended 1 week later. Laboratory tests detected Cryptosporidium oocysts in 9 cases all of whom were 3-13 months old. Further the symptoms (mean duration 14 days, fever [mean peak 38.6 degrees Celsius, and vomiting] matched those of other reported Cryptosporidium diarrhea outbreaks. The epidemic curve suggested a common source of the outbreak. Since the infants received intravenous feedings or sterilized formula, food and water could not have been the source. The physicians believed the AIDS case was that source. Direct person to person transmission was probably not responsible since each infant had his/her own separate crib. Even though the physicians could not conclusively identify the vehicle of transmission, it was most likely the hands of hospitals staff either directly by touching the infants or by contaminating the nasogastric tubes. After the outbreak, the physicians observed that only 30% of medical personnel indeed washed their hands before caring for an infant. 4 previous studies on nosocomial Cryptosporidium diarrhea outbreaks also reported the source case as immunodeficient, but these studies only included adults.^ieng

Epidemic transmission of enterically transmitted non-A, non-B hepatitis in Mexico, 1986-1987.

Outbreaks of acute hepatitis occurred in Huitzililla and Telixtac, two rural villages 70 miles south of Mexico City, Mexico, in late 1986. The first outbreak began in Huitzililla in June of that year, 1 month after the start of the rainy season. A census revealed 94 icteric case subjects, for an attack rate of 5%; two women died. Attack rates were higher for persons older than 15 years (10%) than for younger persons. A case-control study showed that illness was highly associated with water-related factors. The second outbreak began in August 1986 in Telixtac. There were 129 case subjects, for an attack rate of 6%; one woman died. Epidemiologic findings were similar to those in Huitzililla, except that most disease transmission was not linked to unsafe water sources. None of 62 case subjects in Huitzililla and only 2 of 53 case subjects in Telixtac tested had serological evidence for recent infection with hepatitis A or B. Two of eight stool samples from Huitzililla and one of the eight stool samples from Telixtac were positive by immune electron microscopy for 32- to 34-nm viruslike particles similar to those seen in cases of enterically transmitted non-A, non-B hepatitis from Asia. To our knowledge, these investigations document for the first time the epidemic transmission of enterically transmitted non-A, non-B hepatitis virus in the Americas.

The epidemiology of HIV transmission among paid plasma donors, Mexico City, Mexico.

Screening of blood product donations for antibody to HIV began in Mexico in May 1986. From June to October 1986, the HIV cumulative seroprevalence increased from 6.3 to 9.2% in a commercial plasma collection center. Of the 281 people who donated the antibody-positive units, 62 (22.1%) had documented seroconversion during these 5 months. An epidemiologic study of 54 seropositive and 58 seronegative donors was carried out. The HIV serologic status did not change in any of these donors after repeat testing. Only 13.0% of the seropositives and 15.5% of the seronegatives had any of the known risk factors for AIDS. There was a direct relationship between frequency of plasma donation and the risk of being seropositive. A survey of employees disclosed the frequent re-use of disposable blood collection equipment. We conclude that HIV transmission had probably occurred in this plasma collection center.

PIP: This report provides the results of a study of plasma donor clients from records abstracted between June-October 1986. The purpose was to identify risk factors for HIV infection among donors at the National Center for Blood Transfusions. Screening for HIV among donors began in May 1986. 54 Seropositive donors were identified and located from 281 and 58 seronegative donors were randomly selected. 16 employees of the plasma collection center were locatable and also included in the study. The results were that seroprevalence increased between June-October from 6.3% to 9.2%. The total donations were 3201 of which 294 were seropositive. Of 281 seropositive clients, 62 (22%) had seroconversion (a prior seronegative donation). Seroconversions increased from 1.6% in July to 50% in October. On retesting of the 112 study participants, no change in status was found. The groups were similar and both groups had relatively low risk factors for (13% for HIV seropositive and 15.5% for HIV seronegative donors). The rate of seropositivity increased with the frequency of plasma donations from 19.6% for those donating 1-3 times/month to 88.9% for those donating 10 times/month. Of the 16 employees, 1 died who was HIV seropositive; 5 were directly involved in plasma collection and reported reuse of saline solution and intravenous tubing. The results lead the authors to suggest that HIV was transmitted in the collection process. Support for this suggestion comes from the number of seroconversions; the risk factors among the seropositive donors had no known risk factors. Although not statistically significant, male seropositive donors had greater contract with prostitutes in Mexico City, but prostitutes had shown in the past 2 years a seropositivity rate of 1%. More demonstrative evidence comes from the increased rate of seropositivity with frequency of donation, and the employee reports of reutilization of blood collection materials. Other studies have postulated plasma donor site risk. Regardless of the expense of intravenous equipment, it is suggested that the risk of HIV transmission precludes reuse of materials. At present, all blood is collected from volunteer donors with disposable equipment. Other countries need to assess the safety of blood donor centers, particularly with paid donors.

[Tuberculosis surveys in Guerrero and new estimates of the magnitude of tuberculosis infection in Mexico]. / Encuestas tuberculínicas en Guerrero y nuevas estimaciones de la magnitud de la infección tuberculosa en México.

Tuberculosis infection surveys are carried out by tuberculin skin test (Mantoux) which is a simple, cheap, valid and reliable procedure for the estimation of prevalence and incidence rates. In 1987 a survey was undertaken in children of 6-7 years old who attended the elementary school and who were not vaccinated (BCG) in the region of Iguala, México. Out of 6,095 children of such age group, just 531 were not vaccinated, thus the prevalence figure was 2.5% (CL05 = 0.1%, 5.3%). On the basis of the findings by Izaguirre et al, 26 years ago, who reported that about 10% of the children of this age group were infected, it can be estimated that the annual risk of infection is about three newly infected each year per 1,000 population. It is necessary to provide better estimates of the whole tuberculosis incidence rate.

Aetiological agent of enterically transmitted non-A, non-B hepatitis.

Virus-like particles (VLPs) with a mean diameter of 32 nm were recovered from the stools of three acute phase cases of enterically transmitted non-A, non-B hepatitis (ET-NANBH) occurring in the Soviet Union, North Africa and North America. VLPs from two of these cases were studied in detail and were shown to react specifically with antibody in acute phase sera obtained from other cases of ET-NANBH in Asia, the Soviet Union, North Africa and North America. Partially purified VLPs were found to sediment at 183S in sucrose gradients and to cross-react with antibody in acute phase sera from geographically isolated cases of ET-NANBH. The latter virus preparations were also used to document the seroconversion of experimentally ET-NANBH-infected cynomolgus macaques to 32 nm VLPs. Our findings indicate that one virus or class of viruses is responsible for the majority of ET-NANBH.

Monitoring system for adverse events following immunization.

The Monitoring System for Adverse Events Following Immunization (MSAEFI) has collected data from the public sector nationwide on adverse events occurring during the 4-week period following administration of vaccine. From 1979 to 1984, 6483 reports were received. Although rates of reporting have increased throughout the 6-year period, increases were larger for less serious events (209%) than for more serious events (53%). The MSAEFI data have been used to evaluate risk factors for adverse events following immunization, will continue to provide information on the safety of both current and future vaccines and may identify other factors that increase the risks of adverse events following immunization.

An outbreak of influenza A in a nursing home.

An outbreak of influenza A occurred in an elderly population in a Maryland nursing home between December 8, 1980 and January 13, 1981 and involved 76 of the 170 residents. Throat swabs from two of 10 acutely ill residents yielded influenza A virus similar to the A/Taiwan/1/79 strain. Fourfold or greater increases in the titer of complement-fixing (CF) or hemagglutination-inhibiting (HI) antibodies were detected in paired sera from four of five ill residents and from none of four well residents. One hundred (62.9 per cent) of 159 residents with known vaccination histories had been vaccinated with trivalent influenza virus vaccine in October and November 1980. Crude illness attack rates and mortality rates were similar in vaccinees and nonvaccinees. Various risk factors and hypotheses were examined in an attempt to explain the apparent lack of vaccine efficacy.

Impact of revaccinating children who initially received measles vaccine before 10 months of age.

Two hundred fifty-four infants who had received measles vaccine at less than 10 months of age were revaccinated at greater than or equal to 15 months of age, and their immune responses were compared with 129 control infants who received their first doses of measles vaccine at greater than or equal to 15 months of age. Sera were collected at the time of revaccination (study infants) or primary vaccination (control infants), 3 weeks, and 8 months later and tested for antibody by hemagglutination inhibition (HI), enzyme-linked immunosorbent assay (ELISA), and cytopathic effect neutralization (CPEN). Of the 121 study infants who were initially HI negative, 116 (95.9%) made HI antibody 3 weeks postrevaccination compared with 126 (99.2%) of 127 control infants (P = 0.19). Of the 63 study infants with no initial detectable antibody by any of the three tests, 14 (22.2%) had a measles-specific IgM response 3 weeks postrevaccination compared with 37 of 50 (74.0%) randomly chosen control infants. By 8 months after revaccination, the 121 initially HI-negative study infants were significantly less likely to have detectable HI antibodies than control infants (52.1% v 97.6%) (P less than .001). However, 96.7% of these 121 study infants had detectable neutralizing antibody 8 months postrevaccination, an antibody thought to correlate best with protection. This study confirms the altered immune response to revaccination in infants first vaccinated prior to 10 months of age; however, the data suggest that most of these infants were successfully primed and are probably protected after revaccination.

Health impact of measles vaccination in the United States.

As a result of intensive efforts to vaccinate children, measles and its attendant complications of encephalitis and death have declined more than 99% from the prevaccine era. Similarly, subacute sclerosing panencephalitis has declined markedly. Measles vaccine has been demonstrated to be extremely safe, as well as extremely effective. The health and resource benefits due to vaccination against measles during the first 20 years of vaccine licensure have been enormous. In this period it is estimated that vaccination against measles has prevented 52 million cases, 5,200 deaths, and 17,400 cases of mental retardation, achieving a net savings of $5.1 billion. These substantial health and resource benefits of measles vaccination will continue to accrue in the future.

History of convulsions and use of pertussis vaccine.

Data on 2062 reports from the Monitoring System for Adverse Events Following Immunization, Centers for Disease Control (CDC), were analyzed to compare the risk of a personal or family history of convulsions in children who had a neurologic adverse event after receipt of diphtheria-tetanus-pertussis (DTP) vaccine with those who had a nonneurologic adverse event. Children with a neurologic event after DTP vaccine had a 7.2 times higher risk for personal history of convulsions (95% confidence limits 4.5 to 11.5) and a 4.5 times higher risk for family history of convulsions (95% confidence limits 3.1 to 6.7) than did children with an adverse event that did not affect the nervous system. Children with either a febrile or nonfebrile convulsion after receipt of DTP were significantly more likely to have a personal history of convulsions than children with a nonneurologic adverse event (P less than 0.0001). Children with a febrile convulsion after receipt of DTP but not children with nonfebrile convulsions were significantly more likely to have a family history of convulsions than those with a nonneurologic adverse event. It is recommended that pertussis vaccination be deferred in children with a personal history of a convulsion until it can be determined that an evolving neurologic disorder is not present. If such disorders are found, these children should be given the combined pediatric diphtheria and tetanus toxoids (DT) vaccine to complete the series.

Clinical mumps vaccine efficacy.

From February 5 through April 23, 1982, 110 cases of mumps were reported among 357 students in a middle school in Ashtabula County, Ohio, an overall attack rate of 31%. Vaccine efficacy was calculated using a variety of case definitions, case surveillance systems, and vaccination-status ascertainment methods to evaluate their effects on the estimated vaccine efficacy. From data collected at the school for case ascertainment and vaccination status, clinical vaccine efficacy was initially estimated at 37%. By means of a uniform case definition (parotitis lasting two days or more) and only cases and vaccination status ascertained from parental questionnaires, estimated vaccine efficacy increased to 70%. From secondary attack rates in household members with provider-verified vaccination status, the vaccine efficacy further increased to 85%. This outbreak investigation confirms that the methods used to ascertain cases and determine vaccination status greatly affect estimates of vaccine efficacy. Studies relying solely on school records for case finding and determination of immunization status may provide misleadingly low estimates of vaccine efficacy for mumps vaccine as well as for other vaccines. Appropriate methods demonstrate that mumps vaccine is highly effective and support recommendations for its continued use.

Fetal risk associated with rubella vaccine: an update.

One hundred nineteen women susceptible to rubella received RA27/3 vaccine, 94 received either Cendehill or HPV-77 vaccine, and one received a vaccine of unknown strain in the three months before or after their estimated date of conception. They gave birth to 216 living infants free of abnormalities compatible with the congenital rubella syndrome (CRS). The maximum theoretical risk for CRS for these infants was 1.7%. Four of these infants born to susceptible women had laboratory evidence of subclinical infection (three after receiving Cendehill or HPV-77 vaccines and one after receiving RA27/3 vaccine) but were normal at birth and at subsequent follow-up examinations. Rubella virus was isolated from the products of conception for only 3% (1 of 32) of cases involving susceptible women who received RA27/3 vaccine; the reported rate of virus isolation for Cendehill and HPV-77 vaccine is 20%. The available data indicate that if vaccination occurs within three months of conception, the risk is negligible. However, since the actual risk may not be zero, women known to be pregnant should not be vaccinated, and conception should be avoided for three months after vaccination.

Outbreaks of group A streptococcal abscesses following diphtheria-tetanus toxoid-pertussis vaccination.

Two outbreaks of group A streptococcal abscesses following receipt of diphtheria-tetanus toxoid-pertussis (DTP) vaccine from different manufacturers were reported to the Centers for Disease Control (CDC) in 1982. The clustering of the immunization times of cases, the isolation of the same serotype of Streptococcus from all cases in each outbreak, and the absence of reported abscesses associated with receipt of the same lots of vaccine in other regions of the country, suggest that each outbreak was probably caused by contamination of a single 15-dose vial of vaccine. The preservative thimerosal was present within acceptable limits in unopened vials from the same lot of DTP vaccine in each outbreak. Challenge studies indicate that a strain of Streptococcus from one of the patients can survive up to 15 days in DTP vaccine at 4 degrees C. Contamination of vials during manufacturing would have required survival of streptococci for a minimum of 8 months. Preservatives in multidose vaccine vials do not prevent short-term bacterial contamination. Options to prevent further clusters of streptococcal abscesses are discussed. The only feasible and cost-effective preventive measure now available is careful attention to sterile technique when administering vaccine from multidose vials.

Adverse events following immunization with DTP vaccine.

The Monitoring System for Adverse Events Following Immunization became fully operational in late 1978 in all 50 States, New York City and Washington, D.C. This system compiles information on adverse events temporally associated (within four weeks) to the administration of a vaccine. A total of 2,062 reports of adverse events following diphtheria and tetanus toxoids and pertussis vaccine (DTP) were received between 1979 and 1982. The number of reports received in 1979 was 387, increasing to 707 reports in 1982. The increase is predominantly in local reactions and fever. The number of persons with serious illnesses temporally associated with vaccine remained relatively constant over the four year period. The overall rate of reported adverse events following DTP (70.8 per million doses administered in the public sector) was about twice that of Td (33.5) or DT (38.4); however it was not substantially different from those following measles- or rubella-containing vaccines. Those who had convulsions (whether febrile or non-febrile) following receipt of DTP vaccine were substantially more likely to have had a personal history of convulsions than those who had a non-neurologic adverse event following DTP (p less than 0.0001). This information, along with data from the literature, has led to recent recommendations by advisory groups in the United States that any infant or child with a personal history of convulsions should be thoroughly evaluated before initiating or continuing immunization with pertussis vaccine.