Improved estimation of the initial number of susceptible individuals in the general stochastic epidemic model using penalized likelihood.

The initial size of a completely susceptible population in a group of individuals plays a key role in drawing inferences for epidemic models. However, this can be difficult to obtain in practice because, in any population, there might be individuals who may not transmit the disease during the epidemic. This short note describes how to improve the maximum likelihood estimators of the infection rate and the initial number of susceptible individuals and provides their approximate Hessian matrix for the general stochastic epidemic model by using the concept of the penalized likelihood function. The simulations of major epidemics show significant improvements in performance in averages and coverage ratios for the suggested estimator of the initial number in comparison to existing methods. We applied the proposed method to the Abakaliki smallpox data.

Preparing for biological threats: Addressing the needs of pregnant women.

Intentional release of infectious agents and biological weapons to cause illness and death has the potential to greatly impact pregnant women and their fetuses. We review what is known about the maternal and fetal effects of seven biological threats: Bacillus anthracis (anthrax); variola virus (smallpox); Clostridium botulinum toxin (botulism); Burkholderia mallei (glanders) and Burkholderia pseudomallei (melioidosis); Yersinia pestis (plague); Francisella tularensis (tularemia); and Rickettsia prowazekii (typhus). Evaluating the potential maternal, fetal, and infant consequences of an intentional release of an infectious agent requires an assessment of several key issues: (1) are pregnant women more susceptible to infection or illness compared to the general population?; (2) are pregnant women at increased risk for severe illness, morbidity, and mortality compared to the general population?; (3) does infection or illness during pregnancy place women, the fetus, or the infant at increased risk for adverse outcomes and how does this affect clinical management?; and (4) are the medical countermeasures recommended for the general population safe and effective during pregnancy? These issues help frame national guidance for the care of pregnant women during an intentional release of a biological threat. Birth Defects Research 109:391-398, 2017.© 2017 Wiley Periodicals, Inc.

Viral diseases of the skin, 1975: a 25-year perspective.

Most of the major advances in modern virology during the past 25 years have been due principally to the development of refined laboratory techniques and tools and have provided a fund of new knowledge and information about the nature of viral infection and pathogenesis. One group of viruses of interest to dermatologists, the herpesviruses, is undergoing intensive biochemical investigation to determine whether it is carcinogenic. As a result of the success of the World Health Organization's campaign to eradicate smallpox, it is predicted that by the end of 1976, smallpox will have been eradicated. Other viruses of dermatologic interest which are now being studied include the agents of warts, molluscum contagiosum, cat-scratch disease, and enteroviruses. Current research in the field of viral chemotherapy may provide the basis for successfully treating these diseases in the future.

Variola virus immune evasion proteins.

Variola virus, the causative agent of smallpox, encodes approximately 200 proteins. Over 80 of these proteins are located in the terminal regions of the genome, where proteins associated with host immune evasion are encoded. To date, only two variola proteins have been characterized. Both are located in the terminal regions and demonstrate immunoregulatory functions. One protein, the smallpox inhibitor of complement enzymes (SPICE), is homologous to a vaccinia virus virulence factor, the vaccinia virus complement-control protein (VCP), which has been found experimentally to be expressed early in the course of vaccinia infection. Both SPICE and VCP are similar in structure and function to the family of mammalian complement regulatory proteins, which function to prevent inadvertent injury to adjacent cells and tissues during complement activation. The second variola protein is the variola virus high-affinity secreted chemokine-binding protein type II (CKBP-II, CBP-II, vCCI), which binds CC-chemokine receptors. The vaccinia homologue of CKBP-II is secreted both early and late in infection. CKBP-II proteins are highly conserved among orthopoxviruses, sharing approximately 85% homology, but are absent in eukaryotes. This characteristic sets it apart from other known virulence factors in orthopoxviruses, which share sequence homology with known mammalian immune regulatory gene products. Future studies of additional variola proteins may help illuminate factors associated with its virulence, pathogenesis and strict human tropism. In addition, these studies may also assist in the development of targeted therapies for the treatment of both smallpox and human immune-related diseases.

Variola virus strains of 1960--1975: the range of intraspecies variability and relationship between properties and geographic origin.

A comparative study of 61 variola virus strains recovered from patients in various geographic regions of the world revealed significant intraspecies variability in some biological properties, established the range of this variability and demonstrated the existence of strains with atypical properties. There was a certain correlation between some laboratory markers of variola virus and the degree of its pathogenicity for man. The prevalence of more virulent and thermoresistant strains in the Hindustan subcontinent and the peculiarity and heterogeneity of the strains circulating in Africa were demonstrated. Alastrim virus was detected among the African isolates.

Pulmonary manifestations of other agents: brucella, Q fever, tularemia and smallpox.

Brucella, Q fever, tularemia, and smallpox are all rare infections in the United States but are potential agents of biologic terrorism. The pulmonary manifestations of these infections range from uncommon (brucella and smallpox) to expected (Q fever and tularemia). and all have clinical and radiologic presentations that can be confused with other, more endemic,diseases. Once the release of these agents has been determined, the diagnosis of presenting patients will be straightforward. The onus is on the clinician,however, to be able to recognize the first few, unexpected cases, because early identification will be paramount in helping curb the effect of the outbreak.

[Use of electron microscopy for the rapid diagnosis of poxvirus diseases (smallpox) in swine]. / Vyuzití elektronové mikroskopie k rychlé diagnostice poxvirového onemocnení (nestovic) prasat

For a rapid proving of the pig pox virus in the skin of naturally infected pigs, the simple electron microscopic method of negative staining was used. The result was checked by means of the finding of intracytoplasmatic inclusions in the histological sections and the proving of the presence of virions in the ultra-thin sections through the cells of the epidermis.

Bioterrorism: pathogens as weapons.

Biowarfare has been used for centuries. The use of biological weapons in terrorism remains a threat. Biological weapons include infectious agents (pathogens) and toxins. The most devastating bioterrorism scenario would be the airborne dispersal of pathogens over a concentrated population area. Characteristics that make a specific pathogen a high-risk for bioterrorism include a low infective dose, ability to be aerosolized, high contagiousness, and survival in a variety of environmental conditions. The most dangerous potential bioterrorism agents include the microorganisms that produce anthrax, plague, tularemia, and smallpox. Other diseases of interest to bioterrorism include brucellosis, glanders, melioidosis, Q fever, and viral encephalitis. Food safety and water safety threats are another area of concern.