Smallpox as a bioterrorist weapon: myth or menace?

Repositioning potentials of smallpox vaccines and antiviral agents in monkeypox outbreak: A rapid review on comparative benefits and risks

Background and aims

There is a sought for vaccines and antiviral agents as countermeasures for the recent monkeypox outbreak. Here, we aimed to review and discuss the repurposing potentials of smallpox vaccines and drugs in monkeypox outbreaks based on their comparative benefits and risks. Therefore, we conducted this rapid review and discussed the repurposing potentials of smallpox vaccines and drugs in monkeypox infection.

Methods

Here, we searched Google Scholar and PubMed for relevant information and data. We found many articles that have suggested the use of smallpox vaccines and antiviral drugs in monkeypox outbreaks according to the study findings. We read the relevant articles to extract information.

Results

According to the available documents, we found two replication‐competent and one replication‐deficient vaccinia vaccines were effective against Orthopoxvirus. However, the healthcare authorities have authorized second‐generation live vaccina virus vaccines against Orthopoxvirus in many countries. Smallpox vaccine is almost 85% effective in preventing monkeypox infection as monkeypox virus, variola virus, and vaccinia virus are similar. The United States and Canada have approved a replication‐deficient third‐generation smallpox vaccine for the prevention of monkeypox infection. However, the widely used second‐generation smallpox vaccines contain a live virus and replicate it into the human cell. Therefore, there is a chance to cause virus‐induced complications among the vaccinated subjects. In those circumstances, the available Orthopoxvirus inhibitors might be a good choice for treating monkeypox infections as they showed similar efficacy in monkeypox infection in different animal model clinical trials. Also, the combined use of antiviral drugs and vaccinia immune globulin can enhance significant effectiveness in immunocompromised subjects.

Conclusion

Repurposing of these smallpox vaccines and antiviral agents might be weapons to fight monkeypox infection. Also, we recommend further investigations of smallpox vaccines and Orthopoxvirus inhibitors in a human model study to explore their exact role in human monkeypox infections.

Human mobility and the worldwide impact of intentional localized highly pathogenic virus release

The threat of bioterrorism and the possibility of accidental release have spawned a growth of interest in modeling the course of the release of a highly pathogenic agent. Studies focused on strategies to contain local outbreaks after their detection show that timely interventions with vaccination and contact tracing are able to halt transmission. However, such studies do not consider the effects of human mobility patterns. Using a large-scale structured metapopulation model to simulate the global spread of smallpox after an intentional release event, we show that index cases and potential outbreaks can occur in different continents even before the detection of the pathogen release. These results have two major implications: i) intentional release of a highly pathogenic agent within a country will have global effects; ii) the release event may trigger outbreaks in countries lacking the health infrastructure necessary for effective containment. The presented study provides data with potential uses in defining contingency plans at the National and International level.

Orthopoxvirus inhibitors that are active in animal models: an update from 2008 to 2012

Antiviral agents are being sought as countermeasures for the potential deliberate release of smallpox (variola) and monkeypox viruses, for the treatment of naturally acquired monkeypox virus infections, and as therapy for complications due to smallpox (live-attenuated vaccinia virus) vaccination or accidental infection after exposure to vaccinated persons. Reviews of the scientific literature spanning 1950-2008 have documented the progress made in developing small-animal models of poxvirus infection and identifying novel antiviral agents. Compounds of considerable interest include cidofovir, CMX001 and ST-246® (tecovirimat; SIGA Technologies, NY, USA). New inhibitors have been identified since 2008, most of which do not exhibit the kind of potency and selectivity required for drug development. Two promising agents include 4'-thioidoxuridine (a nucleoside analog) and mDEF201 (an adenovirus-vectored interferon). Compounds that have been effectively used in combination studies include vaccinia immune globulin, cidofovir, ST-246 and CMX001. In the future there may be an increase in experimental work using active compounds in combination.

Aptamers recognizing glycosylated hemagglutinin expressed on the surface of vaccinia virus-infected cells

Traditional methods for detection and identification of pathogenic viruses or bacteria tend to be slow and cumbersome. We have developed aptamer probes with the capacity to rapidly detect the presence of viral infection with specificity and sensitivity. Vaccinia virus (VV) was chosen as the model because it is closely related to variola virus that causes smallpox. A method known as cell-SELEX (systematic evolution of ligands by exponential enrichment) was used to generate very selective and highly specific aptamers designed to recognize proteins expressed on the surface of VV-infected cells. Characterization of the aptamers showed that the virus-encoded hemagglutinin, a protein expressed on the surface of infected cells, is the preferential binding target. These studies show the feasibility of generating aptamers against a given specific infectious agent and will enable further development of aptamers as diagnostic and/or therapeutic tools against a broad range of infectious agents.

Responding to suspected smallpox cases in the Los Angeles County from 2002 to 2006: identifying areas for education

INTRODUCTION

Although smallpox has been eradicated, health care providers in emergency departments (EDs) need to remain vigilant to its recognition. Smallpox can be confused with chickenpox. We describe suspected smallpox cases reported in Los Angeles County from 2002 to 2006 and highlight areas for education.

METHODS

We retrospectively reviewed suspected smallpox reports from 2002 to 2006. Laboratory testing was performed. Photographs of rashes were taken.

RESULTS

Five suspected smallpox cases were reported. Two presented first to an ED. Smallpox was suspected based on rash features. Previous history of chickenpox or varicella vaccination may have caused increased suspicion for smallpox. All 5 were determined to have a final diagnosis of chickenpox. Health care providers notified public health appropriately and responses were immediate.

CONCLUSIONS

Public health investigated 5 suspected smallpox cases in the past 5 years. Two presented initially to EDs. Education differentiating smallpox from chickenpox and collaboration between public health, EDs, and health care providers remains important. The ability to respond rapidly to a potential bioterrorism emergency was tested.

Infectious agents of bioterrorism: a review for emergency physicians

The terrorist attacks on the United States in 2001 and the anthrax release soon after brought the issue of bioterrorism to the forefront in the medical community. Bioterrorism is the use of a biologic weapon to create terror and panic. Biologic weapons, or bioweapons, can be bacteria, fungi, viruses, or biologic toxins. Because the emergency department represents the front line of defense for the recognition of agents of bioterrorism, it is essential that emergency physicians have the ability to quickly diagnose victims of bioterrorism. This review examines the most deadly and virulent category A agents of bioterrorism, that is, anthrax, smallpox, plague, botulism, hemorrhagic fever viruses, and tularemia. The focus is on epidemiology, transmission, clinical manifestations, diagnosis, and treatment.

Progress in the Discovery of Compounds Inhibiting Orthopoxviruses in Animal Models

Surrogate animal models must be used for testing antiviral agents against variola (smallpox) virus infections. Once developed, these compounds can be stockpiled for use in the event of a bioterrorist incident involving either variola or monkeypox virus, or used to treat an occasional serious orthopoxvirus infection, such as disseminated vaccinia complication following expo-sure to the live virus vaccine. Recently, considerable progress has been made in the discovery of novel anti-viral agents found active against orthopoxviruses in vivo. This includes the development of new animal models or refinement of existing ones for compound efficacy testing. Current mouse models employ ectromelia, cowpox and vaccinia (WR and IHD strains) viruses with respiratory (lung) or tail lesion infections commonly studied. Rabbitpox and vaccinia (WR strain) viruses are available for rabbit infections. Monkeypox and variola viruses are used for infecting monkeys. This review describes these and other animal models, and covers compounds found active in vivo from 2003 to date. Cidofovir, known to be active against orthopox virus infections prior to 2003, has been studied extensively over recent years. New compounds showing promise are orally active inhibitors of orthopoxvirus infections that include ether lipid prodrugs of cidofovir and ( S)-HPMPA, ST-246, N-meth-anocarbathymidine ( N-MCT) and SRI 21950 (a 4'-thio derivative of iododeoxyuridine). Another compound with high activity but requiring parenteral administration is HPMPO-DAPy. Further development of these compounds is warranted.

Fever of unknown origin due to zoonoses

Fevers of unknown origin have been classified as classic, nosocomial, immune-deficient, and HIV-related. More than half of the 1407 human pathogens are zoonotic, making zoonotic infections an important subcategory in each of the classifications. This article describes both common and unusual zoonoses causing fevers of unknown origin. Simian immune virus is considered as a possible emerging infection. For special populations (the homeless, zoophiliacs, those whose occupation or leisure brings them in close contact with oceans or lakes, and veterinarians), zoonotic infection potentials are discussed.