J. P. Duguid

Bio: J. P. Duguid is an academic researcher from University of Edinburgh. The author has contributed to research in topics: Shigella flexneri & Blood serum. The author has an hindex of 2, co-authored 2 publications receiving 602 citations.

The size and the duration of air-carriage of respiratory droplets and droplet-nuclei

Abstract: 1. The sizes of the droplets and droplet-nuclei produced by sneezing, by coughing and by speaking, were studied by the microscopic measurement of 12,000 droplet stain-marks found on slides exposed directly to mouth-spray, and of 21,000 stain-containing droplet-nuclei recovered from the air on to oiled slides exposed in the slit sampler. 2. From these measurements it was calculated that the original diameters of the respiratory droplets ranged from 1 to 2000 μ, that 95 % were between 2 and 100 μ and that the most common were between 4 and 8 μ. Similar size distributions were exhibited by the droplets produced in sneezing, in coughing and in speaking, except that, in the case of sneezing, the smaller droplets were relatively more numerous. 3. The respiratory droplet-nuclei were found to range in diameter from ¼ to 42 μ; 97 % had diameters between ½ and 12μ; the commonest diameter was between 1 and 2 μ. 4. The proportion of droplets of each size which will contain bacteria, whether commensal or pathogenic, is determined by the size of the droplets and by the numbers of bacteria in the secretions atomized. Calculations made on the basis of the size distributions obtained in this investigation indicated that few of the smaller droplets, and thus few of the droplet-nuclei, are likely to contain pathogenic organisms. Droplet-spray is unlikely to give rise directly to true airborne infection unless very large numbers of pathogenic organisms are present in the secretions of the anterior mouth. 5. The persistence of droplet-nuclei in the air of a 1700 cu.ft. room and of a 70 cu.ft. chamber was investigated by sampling the air with the slit sampler at intervals following sneezing. 6. When the air was not artificially disturbed by a fan, the time taken for the disappearance from the air of 90% of the bacteria-carrying droplet-nuclei varied from 30 to 60 min.; the nuclei larger than 8 μ in diameter usually disappeared within 20 min., and the nuclei larger than 4 μ within 90 min.; the smaller nuclei, few of which contained bacteria, remained airborne for much longer periods, on one occasion for at least 30 hr. When a fan was run throughout the experiment, the nuclei disappeared from the air much more rapidly.

The fimbrial antigens of Shigella flexneri.

Abstract: 1. ‘Pure fimbrial antisera’ were prepared for Sh. flexneri strains of O-serotypes 1a, 2b, 3 and 4a and 5, by injecting rabbits with a living fimbriate-phase culture and absorbing the crude immune serum with a non-fimbriate-phase culture of the same strain to remove antibodies for the non-fimbrial (somatic) antigens. These sera gave at high titre a rapid, loosely floccular agglutination of all fimbriate-phase Flexneri cultures, caused adhesion of their fimbriae visible by electron-microscopy and inhibited their haemagglutinating activity. ‘Non-fimbrial antisera’, prepared by injection of non-fimbriate-phase cultures, were devoid of these activities; they gave somatic-type agglutination with fimbriate bacilli at lower titres than with homologous non-fimbriate bacilli, the fimbriae tending to mask the O-antigens and confer relative O-inagglutinability.2. Heating at 90°C. detached the fimbriae from the bacilli, so that these lost their haemagglutinating activity, fimbrial serum agglutinability and fimbrial agglutinin-binding power. When heated for 21/2 hr. at 100°C., the detached fimbriae retained agglutinin-binding power, but lost their immunogenicity.3. Cross-agglutination and absorption tests showed that the antigenic composition of the fimbriae was identical in all flexneri strains, irrespective of O-serotype. The flexneri pure fimbrial antisera agglutinated at low titre sixty out of sixty-six fimbriate Bact. coli strains. Absorption tests with a flexneri and three coli pure fimbrial antisera showed that the fimbriae of Sh. flexneri contained a major ‘flexneri-specific antigen’, found in only one coli strain, one or more minor ‘flexneri-coli antigens’ shared by a few coli strains. The coli fimbriae also contained a major, ‘coli type-specific antigen’ shared in groups of several related strains. The flexneri sera did not react with fimbriate strains of Bact. cloacae, Salmonella and Proteus.4. Fimbrial agglutinins for Sh. flexneri were found in eighty of eighty-one normal human sera at titres from 30 to 1920, and in some pre-immunization rabbit sera at titres of 30 to 60.

Smallpox and its eradication

Abstract: worked for the smallpox eradi-cation programme in western Africa in 1962-1963 as a member of the staff of the W H O Regional Office for Africa. In 1964 he was transferred t o W H O Headquarters in Geneva, and in 1966 he joined the Smallpox Eradication unit, of which he was Chief from 1977 until 1984. He is now Director of the Kumamoto National Hospital in Japan and a member of the advisory group on international health of the Ministry of Health and Welfare of Japan. while at the Communicable Disease Center in the USA, was responsible in 1965-1 966 for the planning of the western and central African smallpox eradication-measles control programme, conducted with the support of the United States Agency for International Development. USSR from 1983 until his death in 1987. T h e authors alone are responsible for t h e views expressed i n t h i s publication. The World Health Organization welcomes such applications. The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the World Health Organization concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. The mention of specific companies or of certain manufacturers' products does not imply that they are endorsed or recommended by the World Health Organization in preference to others of a similar nature that are not mentioned. Errors and omissions excepted, the names of proprietary products are distinguished by initial capital letters.

Guideline for isolation precautions: preventing transmission of infectious agents in healthcare settings 2007.

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Absolute humidity modulates influenza survival, transmission, and seasonality

Abstract: Influenza A incidence peaks during winter in temperate regions. The basis for this pronounced seasonality is not understood, nor is it well documented how influenza A transmission principally occurs. Previous studies indicate that relative humidity (RH) affects both influenza virus transmission (IVT) and influenza virus survival (IVS). Here, we reanalyze these data to explore the effects of absolute humidity on IVT and IVS. We find that absolute humidity (AH) constrains both transmission efficiency and IVS much more significantly than RH. In the studies presented, 50% of IVT variability and 90% of IVS variability are explained by AH, whereas, respectively, only 12% and 36% are explained by RH. In temperate regions, both outdoor and indoor AH possess a strong seasonal cycle that minimizes in winter. This seasonal cycle is consistent with a wintertime increase in IVS and IVT and may explain the seasonality of influenza. Thus, differences in AH provide a single, coherent, more physically sound explanation for the observed variability of IVS, IVT and influenza seasonality in temperate regions. This hypothesis can be further tested through future, additional laboratory, epidemiological and modeling studies.

The airborne lifetime of small speech droplets and their potential importance in SARS-CoV-2 transmission.

Abstract: Speech droplets generated by asymptomatic carriers of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are increasingly considered to be a likely mode of disease transmission. Highly sensitive laser light scattering observations have revealed that loud speech can emit thousands of oral fluid droplets per second. In a closed, stagnant air environment, they disappear from the window of view with time constants in the range of 8 to 14 min, which corresponds to droplet nuclei of ca. 4 μm diameter, or 12- to 21-μm droplets prior to dehydration. These observations confirm that there is a substantial probability that normal speaking causes airborne virus transmission in confined environments.