Francis L. Black

Measles endemicity in insular populations: critical community size and its evolutionary implication.

Abstract Monthly measles case reports from 19 island communities covering periods up to 15 years have been analyzed. Breaks in the continuity of measles transmission were found for all communities of less than 500,000 population. The duration of epidemics was also affected by population density. It is postulated that populations sufficient to support continued propagation of this virus did not exist in primitive societies and that measles virus must have evolved since the development of early civilizations.

Human Herpesvirus 8 in Brazilian Amerindians: A Hyperendemic Population with a New Subtype

Human herpesvirus 8 (HHV-8) epidemiology in Brazilian Amerindians was studied. Use of an immunofluorescence (IFA) test for latent antibody demonstrated that the prevalence of HHV-8 in 781 Amerindians of diverse tribes (overall, 53% prevalence) was not related to language group or sex but rather increased gradually from 41% in children <10 years of age to 65% in adults >/=30 years of age. In IFA-positive subjects, HHV-8 DNA was detected in 3 (16%) of 19 mononuclear cell samples from peripheral blood and in 1 of 16 saliva samples. The sequences of conserved ORF22 and K6 genes were typical of HHV-8, but the variable K1 gene sequences were only 70%-75% identical to other known HHV-8 strains. Thus, a new HHV-8 subtype, E, is hyperendemic in Brazilian Amerindians, although Kaposis sarcoma has not been reported. Transmission is probably oral rather than sexual. The limited genetic pool in isolated groups may permit more frequent transmission of a virus with a low prevalence in heterogeneous populations.

HLA and Mate Selection: No Evidence in South Amerindians

There have been reports of nonrandom mating (negative-assortative mating) or preference for individuals of different major histocompatibility complex (MHC) genotypes in both mice and humans. We have examined the association of HLA-A and HLA-B genotypes, both for each locus by itself and for two-locus genotypes, in mates of 194 couples from 11 South Amerindian tribes. The proportion of couples sampled averaged >50% of the total matings with progeny for 10 of the tribes. In nearly all cases, HLA-sharing proportions were very close to those expected from random mating, suggesting strong negative-assortative mating for MHC is not present in these South Amerindians.

Maternally derived measles immunity in era of vaccine-protected mothers

Measles hemagglutinin-inhibiting and neutralizing antibody titers are lower in women young enough to have been immunized by vaccination than in older women. In the children of both young and older mothers the antibody is concentrated 1.7-fold across the placenta, and the childs initial titer remains proportional to that of its mother. The transferred antibody is diluted by the babys growth and degraded with a mean half-life of 48 days. By 8 1/2 months of age, 95% of the children of the mothers born since 1963 would have become susceptible to measles and responsive to immunization; the same level of susceptibility is not reached by children of mothers born before 1958 until 11 1/2 months of age. Among the offspring of younger mothers, a small group remains, about 2% of the total, with titers high enough to provide protection for 12 months, and these children would be poorly served if the age for vaccination were reduced for all. However, selective early vaccination of children of young mothers who have low antibody titers would eliminate an important focus of measles susceptibility.

Growth and stability of measles virus

Abstract The growth of measles virus in Hep-2 cultures has been investigated. Maturation of the first new virus occurred 15–18 hours after inoculation, but no virus was released into the fluid phase for 27–30 hours. Even after this time the major part of the active virus remained with the cells. At 37° the virus had a half-life of about 2 hours. Thus there was little accumulation of live virus in tissue culture fluid but during the period of active virus production there was an equilibrium between release and decay. The virus was relatively stable when suspended in media at 0° of pH 6 to 9, but titer was rapidly lost at 4.5 and lower.

Reported measles in persons immunologically primed by prior vaccination

REPORTED MEAsLEs CASES in the United States in 1981 were only one per thousand births, whereas previously essentially all children had measles. Nevertheless, epidemic measles still occurs, v3 Recent outbreaks have involved a greater proportion of cases in older children and teenagers, 4.5 many of whom were thought to be immune because they had received iive vaccine according to the recommended guidelines. 6 This communication describes serologic analyses of measles antibody in specimens from 22 cases in a recent outbreak. M E T H O D S

Genetic variation within the Tupi linguistic group: new data on three Amazonian tribes

A total of 505 individuals belonging to four populations of three Brazilian Indian tribes were variously studied in relation to 34 genetic systems, and the results were compared with South American Indian averages and five other Tupi populations. Rare variants (CdE of the Rh system, PGM211-1, Cp A-CAY1, serum cholinesterase2 C5+ and some Gm combinations) were observed with varying prevalences, and the three tribes showed different degrees of departure (28%-40% of differences of 10% or more in gene frequencies) from South American Indian averages. People from two communities who speak the same language and are labelled as belonging to the same tribe (Asurini) showed a large degree of genetic differentiation. Another of the tribes studied (Urubu-Kaapor) link through genetic distance analyses with two other tribes from the north of the continent, forming a distinct microevolutionary unit. These features emphasize the peculiarities of the genetic variation in populations with a hunter-gatherer, rudimentary agriculture type of economy.

Epidemiology of Paramyxoviridae

All Paramyxoviridae are extremely infectious, and there is little chance for anybody living in a cosmopolitan community to get through a full life without being infected by wild or attenuated forms of all the paramyxoviruses adapted to humans. Their common structure is labile and all viruses of this family are dependent on transmission by close association of hosts. They do not survive drying on a solid surface, nor are they sufficiently stable in water to be transmitted by this vehicle with regularity. They are inactivated by stomach acid and intestinal enzymes, and do not infect via the gut. Very efficient infection occurs through aerosolized virus, and direct physical contact between hosts is not required. Drying in an aerosol does not inactivate them and it is probably the surface tension forces involved in drying on a surface, not drying per se, that inactivates. Urine may be an important source of the aerosols (Gresser and Katz, 1960). These viruses infect through mucous membranes (Papp, 1956; Black and Sheridan, 1960), but measles virus, at least, infects most efficiently when introduced in droplets small enough to reach into the lungs (McCrumb et al., 1962).

Helicobacter pylori Prevalence among Indigenous Peoples of South America

The seroprevalence of Helicobacter pylori among secluded Indian populations of South America was determined to gain insight into the evolutionary history and possible transmission patterns of the organism. Serum samples obtained from 1024 donors in 22 different villages were tested by enzyme-linked immunosorbent assay for immunoglobulin G antibodies, and the results were confirmed by Western blot. The overall seroprevalence was 92%: >80% of children tested positive by 3 years of age, the highest prevalence in populations studied to date. Comparison of H. pylori prevalence with that of herpes simplex virus type 1, which is known to be transmitted orally, demonstrated a linear correlation in their prevalence rates, suggesting that these pathogens share risk factors. However, H. pylori seroprevalence was consistently higher, indicating that additional routes of transmission exist and/or that the organism is more transmissible. Seroprevalence did not correlate with the length of contact with the outside world. These results suggest that H. pylori was indigenous to the South American Indians and was not introduced by contact with outsiders.

Appearance of Soluble and Gross-Reactive Complement-Fixing Antigens on Treatment of Poliovirus with Formalin.

Summary Poliovirus in tissue culture fluid was treated with dilute formaldehyde and fractionated by ultracentrifugation. Most of the complement-fixing antigen in the active virus preparations could be sedimented at 105,000 x gravity for 2 hours. However, in the formalin-treated samples a soluble antigen appeared which remained in the supernatant fluid. The active virus preparations used were almost completely type specific in their complement-fixing reactions, but after treatment with formaldehyde, cross reactions were found between all types.