Influence of Population Immunosuppression and Past Vaccination on Smallpox Reemergence

Mpox (monkeypox) knowledge, concern, willingness to change behaviour, and seek vaccination: results of a national cross-sectional survey

BACKGROUND

In mid-2022, a global mpox (formerly 'monkeypox') outbreak affecting predominantly gay and bisexual men emerged in non-endemic countries. Australia had never previously recorded mpox cases and there was no prior research on knowledge or attitudes to mpox among gay and bisexual men across Australia.

METHODS

We conducted a national, online cross-sectional survey between August 2022 and September 2022. Participants were recruited through community organisation promotions, online advertising, and direct email invitations. Eligible participants were gay, bisexual or queer; identified as male (cisgender or transgender) or non-binary; aged 16years or older; and lived in Australia. The main outcome measures were: knowledge and concern about mpox; recognition of mpox symptoms and transmission routes; vaccination history; acceptability of behavioural changes to reduce mpox risk, and willingness to be vaccinated.

RESULTS

Of 2287 participants, most participants were male (2189/2287; 95.7%) and gay (1894/2287; 82.8%). Nearly all had heard about mpox (2255/2287; 98.6%), and the majority were concerned about acquiring it (1461/2287; 64.4%). Most of the 2268 participants not previously diagnosed with mpox correctly identified skin lesions (2087; 92%), rash (1977; 87.2%), and fever (1647; 72.6%) as potential symptoms, and prolonged and brief skin-to-skin contact as potential ways to acquire mpox (2124, 93.7%; and 1860, 82%, respectively). The most acceptable behavioural changes were reducing or avoiding attendance at sex parties (1494; 65.9%) and sex-on-premises venues (1503; 66.4%), and having fewer sexual partners (1466; 64.6%). Most unvaccinated and undiagnosed participants were willing to be vaccinated (1457/1733; 84.1%).

CONCLUSIONS

People at risk of mpox should be supported to adopt acceptable risk reduction strategies during outbreaks and to seek vaccination.

Indirect Dispersion of SARS-CoV-2 Live-Attenuated Vaccine and Its Contribution to Herd Immunity

It has been 34 months since the beginning of the SARS-CoV-2 coronavirus pandemic, which causes the COVID-19 disease. In several countries, immunization has reached a proportion near what is required to reach herd immunity. Nevertheless, infections and re-infections have been observed even in vaccinated persons. That is because protection conferred by vaccines is not entirely effective against new virus variants. It is unknown how often booster vaccines will be necessary to maintain a good level of protective immunity. Furthermore, many individuals refuse vaccination, and in developing countries, a large proportion of the population has not yet been vaccinated. Some live-attenuated vaccines against SARS-CoV-2 are being developed. Here, we analyze the indirect dispersion of a live-attenuated virus from vaccinated individuals to their contacts and the contribution that this phenomenon could have to reaching Herd Immunity.

Monkeypox outbreak, vaccination, and treatment implications for the dermatologic patient: Review and interim guidance from the Medical Dermatology Society

Rapid human-to-human transmission of monkeypox has created a public health emergency requiring prompt, multidisciplinary attention. Dermatologists are at the forefront of diagnosis due to the disease-defining skin lesions. Moreover, patients with pre-existing skin disease and those who are on immunosuppressive medications for skin disease may be at increased risk of severe infection. In this review, a panel of authors with expertise in complex medical dermatology and managing patients on immunosuppression reviews the literature and provides initial guidance for diagnosis and management in dermatology practices. Though there are knowledge gaps due to a lack of controlled studies, we support use of replication-deficit vaccines in all dermatologic patients who meet qualifying risk or exposure criteria. We offer strategies to optimize vaccine efficacy in patients with immunosuppression. We discuss alternative post-exposure treatments and their safety profiles. Finally, we outline supportive care recommendations for cutaneous manifestations of monkeypox. Large scale epidemiologic investigations and clinical trials will ultimately revise and extend our guidance.

Modeling on the Effects of Deliberate Release of Aerosolized Inhalational Bacillus anthracis (Anthrax) on an Australian Population

This study aimed to determine optimal mitigation strategies in the event of an aerosolized attack with Bacillus anthracis, a category A bioterrorism agent with a case fatality rate of nearly 100% if inhaled and untreated. To simulate the effect of an anthrax attack, we used a plume dispersion model for Sydney, Australia, accounting for weather conditions. We determined the radius of exposure in different sizes of attack scenarios by spore quantity released per second. Estimations of different spore concentrations were then used to calculate the exposed population to inform a Susceptible-Exposed-Infected-Recovered (SEIR) deterministic mathematical model. Results are shown as estimates of the total number of exposed and infected people, along with the burden of disease, to quantify the amount of vaccination and antibiotics doses needed for stockpiles. For the worst-case scenario, over 500,000 people could be exposed and over 300,000 infected. The number of deaths depends closely on timing to start postexposure prophylaxis. Vaccination used as a postexposure prophylaxis in conjunction with antibiotics is the most effective mitigation strategy to reduce deaths after an aerosolized attack and is more effective when the response starts early (2 days after release) and has high adherence, while it makes only a small difference when started late (after 10 days).

Optimizing two-dose vaccine resource allocation to combat a pandemic in the context of limited supply: The case of COVID-19

The adequate vaccination is a promising solution to mitigate the enormous socio-economic costs of the ongoing COVID-19 pandemic and allow us to return to normal pre-pandemic activity patterns. However, the vaccine supply shortage will be inevitable during the early stage of the vaccine rollout. Public health authorities face a crucial challenge in allocating scarce vaccines to maximize the benefits of vaccination. In this paper, we study a multi-period two-dose vaccine allocation problem when the vaccine supply is highly limited. To address this problem, we constructed a novel age-structured compartmental model to capture COVID-19 transmission and formulated as a nonlinear programming (NLP) model to minimize the total number of deaths in the population. In the NLP model, we explicitly take into account the two-dose vaccination procedure and several important epidemiologic features of COVID-19, such as pre-symptomatic and asymptomatic transmission, as well as group heterogeneity in susceptibility, symptom rates, severity, etc. We validated the applicability of the proposed model using a real case of the 2021 COVID-19 vaccination campaign in the Midlands of England. We conducted comparative studies to demonstrate the superiority of our method. Our numerical results show that prioritizing the allocation of vaccine resources to older age groups is a robust strategy to prevent more subsequent deaths. In addition, we show that releasing more vaccine doses for first-dose recipients could lead to a greater vaccination benefit than holding back second doses. We also find that it is necessary to maintain appropriate non-pharmaceutical interventions (NPIs) during the vaccination rollout, especially in low-resource settings. Furthermore, our analysis indicates that starting vaccination as soon as possible is able to markedly alleviate the epidemic impact when the vaccine resources are limited but are currently available. Our model provides an effective tool to assist policymakers in developing adaptive COVID-19 likewise vaccination strategies for better preparedness against future pandemic threats.

Lactobacilli Infection Case Reports in the Last Three Years and Safety Implications

Lactobacilli constitute the dominant microbiota in many fermented foods and comprise widely used probiotics. However, these bacteria cause rare infections mostly in diabetic and immunocompromised subjects in presence of risk factors such as prosthetic hearth valves and dental procedures or caries. The scope of this survey was re-assessing the pathogenic potential of lactobacilli based on the infection case reports published in the last three years. In 2019, 2020, and 2021, total of 17, 15, and 16 cases, respectively, including endocarditis, bacteremia, and other infections, were reported. These annual numbers are higher than those observed previously. Lacticaseibacillus rhamnosus (13 cases), comprising strain GG (ATCC 53103) with established applications in healthcare, L. paracasei (7 cases), Lactobacillus acidophilus (5 cases), L. jensenii (5 cases), Lactiplantibacillus plantarum (3 cases), L. paraplantarum, L. delbrueckii subsp. delbrueckii, L. gasseri, L. paragasseri, Limosilactobacillus fermentum, and L. reuteri (1 case each) were involved. Virulence characterization of two strains that caused infections, a derivative of L. rhamnosus GG and L. paracasei LP10266, indicated that increased biofilm-forming capacity favors pathogenicity and it is determined by variable genetic traits. This survey highlights that the strains of lactobacilli that cause infections are little characterized genetically. Instead, to avoid that these bacteria become a hazard, genetic stability should be periodically re-evaluated by whole genome sequencing (WGS) to ensure that only non-pathogenic variants are administered to vulnerable individuals.

Pacific Eclipse - A tabletop exercise on smallpox pandemic response

BACKGROUND

In December 2019, we ran Pacific Eclipse, a pandemic tabletop exercise using smallpox originating in Fiji as a case study. Pacific Eclipse brought together international stakeholders from health, defence, law enforcement, emergency management and a range of other organisations.

AIM

To review potential gaps in preparedness and identify modifiable factors which could prevent a pandemic or mitigate the impact of a pandemic.

METHODS

Pacific Eclipse was held on December 9-10 in Washington DC, Phoenix and Honolulu simultaneously. The scenario began in Fiji and becomes a pandemic. Mathematical modelling of smallpox transmission was used to simulate the epidemic under different conditions and to test the effect of interventions. Live polling, using Poll Everywhere software that participants downloaded onto their smart phones, was used to gather participant decisions as the scenario unfolded. Stakeholders from state and federal government and non-government organisations from The United States, The United Kingdom, Australia, New Zealand, Canada, as well as industry and non-government organisations attended.

RESULTS

The scenario progressed in three phases and participants were able to make decisions during each phase using live polling. The polling showed very diverse and sometimes conflicting decision making. Factors influential to pandemic severity were identified and categorised as modifiable or unmodifiable. A series of recommendations were made on the modifiable determinants of pandemic severity and how these can be incorporated into pandemic planning. These included preventing an attack through intelligence, law enforcement and legislation, improved speed of diagnosis, speed and completeness of case finding and case isolation, speed and security of vaccination response (including stockpiling), speed and completeness of contact tracing, protecting critical infrastructure and business continuity, non-pharmaceutical interventions (social distancing, PPE, border control) and protecting first responders.

DISCUSSION

Pacific Eclipse illustrated the impact of a pandemic of smallpox under different response scenarios, which were validated to some extent by the COVID-19 pandemic. The framework developed from the scenario draws out modifiable determinants of pandemic severity which can inform pandemic planning for the ongoing COVID-19 pandemic and for future pandemics.

Countering the potential re-emergence of a deadly infectious disease-Information warfare, identifying strategic threats, launching countermeasures

Objectives

Eradicated infectious diseases like smallpox can re-emerge through accident or the designs of bioterrorists, and cause heavy casualties. Presently, the populace is largely susceptible as only a small percentage is vaccinated, and their immunity is likely to have waned. And when the disease re-emerges, the susceptible individuals may be manipulated by disinformation on Social Media to refuse vaccines. Thus, a combination of countermeasures consisting of antiviral drugs and vaccines and a range of policies for their application need to be investigated. Opinions regarding whether to receive vaccines evolve over time through social exchanges via networks that overlap with but are not identical to the disease propagation networks. These couple the spread of the biological and information contagion and necessitate a joint investigation of the two.

Methods

We develop a computationally tractable metapopulation epidemiological model that captures the joint spatio-temporal evolution of an infectious disease (e.g., smallpox, COVID-19) and opinion dynamics.

Results

Considering smallpox, the computations based on the model show that opinion dynamics have a substantial impact on the fatality count. Towards understanding how perpetrators are likely to seed the infection, we identify a) the initial distribution of infected individuals that maximize the overall fatality count; and b) which habitation structures are more vulnerable to outbreaks. We assess the relative efficacy of different countermeasures and conclude that a combination of vaccines and drugs minimize the fatalities, and by itself, drugs reduce fatalities more than the vaccine. Accordingly, we assess the impact of increase in the supply of drugs and identify the most effective among a collection of policies for administering of drugs for various parameter combinations. Many of the observed patterns are stable to variations of a diverse set of parameters.

Conclusions

Our findings provide a quantitative foundation for various important elements of public health discourse that have largely been conducted qualitatively.

Modelling of optimal vaccination strategies in response to a bioterrorism associated smallpox outbreak

The reemergence of smallpox as a bioterrorism attack is now an increasing and legitimate concern. Advances in synthetic biology have now made it possible for the virus to be synthesized in a laboratory, with methods publicly available. Smallpox introduction into a susceptible population, with increased immunosuppression and an aging population, raises questions of how vaccination should be used in an epidemic situation when supply may be limited. We constructed three modified susceptible-latent-infectious-recovered (SEIR) models to simulate targeted, ring and mass vaccination in response to a smallpox outbreak in Sydney, Australia. We used age-specific distributions of susceptibility, infectivity, contact rates, and tested outputs under different assumptions. The number of doses needed of second- and third-generation vaccines are estimated, along with the total number of deaths at the end of the epidemic. We found a faster response is the key and ring vaccination of traced contacts is the most effective strategy and requires a smaller number of doses. However if public health authorities are unable to trace a high proportion of contacts, mass vaccination with at least 125,000 doses delivered per day is required. This study informs a better preparedness and response planning for vaccination in a case of a smallpox outbreak in a setting such as Sydney.

COVID-19 pandemic sheds light on the importance of food safety practices: risks, global recommendations, and perspectives

The outbreak of the coronavirus disease (COVID-19) is global health and humanitarian emergency. To respond effectively to this pandemic, it is mandatory to reaffirm science in its different fields of study, including the food safety area. Presently, we review food safety in times of COVID-19, exploring whether the virus can be transmitted by food or water; recommendations from regulatory agencies; perceptions of food hygiene practices during the pandemic; and post-pandemic perspectives. The review was based on papers published in Web of Science, Scopus, Pubmed, and covered recommendations of public health protection and regulatory agencies around the world. The transmission of the severe acute respiratory syndrome (SARS-CoV-2) by food was not confirmed until the present time. In any case, the protocols already established for food safety were reinforced, emphasizing the proper hygiene of hands after shopping, handling food packages, or before manipulating or eating food, adequate social distance, the use of individual protection equipment, the health of employees, and the proper preparation of food. It is hoped, in the post-pandemic scenario, to reach a better understanding of the particularities that led to greater care with food hygiene. Moreover, it is expected that the food system will creatively adapt the way meals are served.

Modelling the impact of a smallpox attack in India and influence of disease control measures

OBJECTIVES

To estimate the impact of a smallpox attack in Mumbai, India, examine the impact of case isolation and ring vaccination for epidemic containment and test the health system capacity under different scenarios with available interventions.

SETTING

The research is based on Mumbai, India population.

INTERVENTIONS

We tested 50%, 70%, 90% of case isolation and contacts traced and vaccinated (ring vaccination) in the susceptible, exposed, infected, recovered model and varied the start of intervention between 20, 30 and 40 days after the initial attack.

PRIMARY AND SECONDARY OUTCOME MEASURES

We estimated and incorporated in the model the effect of past vaccination protection, age-specific immunosuppression and contact rates and Mumbai population age structure in modelling disease morbidity and transmission.

RESULTS

The estimated duration of an outbreak ranged from 127 days to 8 years under different scenarios, and the number of vaccine doses needed for ring vaccination ranged from 16 813 to 8 722 400 in the best-case and worst-case scenarios, respectively. In the worst-case scenario, the available hospital beds in Mumbai would be exceeded. The impact of a smallpox epidemic may be severe in Mumbai, especially compared with high-income settings, but can be reduced with early diagnosis and rapid response, high rates of case finding and isolation and ring vaccination.

CONCLUSIONS

This study tells us that if smallpox re-emergence occurs, it may have significant health and economic impact, the extent of which will depend on the availability and delivery of interventions such as a vaccine or antiviral agent, and the capacity of case isolation and treatment. Further research on health systems requirements and capacity across the diverse states and territories of India could improve the preparedness and management strategies in the event of re-emergent smallpox or other serious emerging infections.

An overview of tecovirimat for smallpox treatment and expanded anti-orthopoxvirus applications

Introduction

Tecovirimat (TPOXX®; ST-246) was approved for the treatment of symptomatic smallpox by the USFDA in July of 2018 and has been stockpiled by the US government for use in a smallpox outbreak. While there has not been a reported case of smallpox since 1978 it is still considered a serious bioterrorism threat.

Areas covered

A brief history of smallpox from its proposed origins as a human disease through its eradication in the late 20th century is presented. The current smallpox threat and the current public health response plans are described. The discovery, and development of tecovirimat through NDA submission and subsequent approval for treatment of smallpox are discussed. Google Scholar and PubMed were searched over all available dates for relevant publications.

Expert opinion

Approval of tecovirimat to treat smallpox represents an important milestone in biosecurity preparedness. Incorporating tecovirimat into the CDC smallpox response plan, development of pediatric liquid and intravenous formulations, and approval for post-exposure prophylaxis would provide additional health security benefit.

Tecovirimat shows broad efficacy against orthopoxviruses in vitro and in vivo and could be developed for use against emerging orthopoxvirus diseases such as monkeypox, vaccination-associated adverse events, and side effects of vaccinia oncolytic virus therapy.

Reevaluating the Risk of Smallpox Reemergence

INTRODUCTION

Smallpox, caused by variola virus, was eradicated in 1980, but remains a category A bioterrorism agent. A decade ago, smallpox ranked second after anthrax in a multifactorial risk priority scoring analysis of category A bioterrorism agents. However, advances in genetic engineering and synthetic biology, including published methods for synthesizing an Orthopoxvirus, require the assumptions of this scoring for smallpox and other category A agents to be reviewed.

MATERIALS AND METHODS

The risk priority framework was reviewed and revised to account for the capability for creation of synthetic or engineered smallpox and other category A agents.

RESULTS

The absolute score for all agents increased because of gene editing and synthetic biology capability, which was not present when the framework was developed more than a decade ago, although new treatments revised scores downward for smallpox, Ebola, and botulism. In the original framework, smallpox scored 0 for global availability, given the high security around known seed stocks of variola in two laboratories in the United States and Russia. Now, smallpox can be created using synthetic biology, raising the score for this criterion to 2. Other agents too, such as Ebola, score higher for availability, based on synthetic biology capability. When advances in synthetic biology and genetic engineering are considered, smallpox and anthrax are now equally ranked the highest category A bioterrorism agents for planning and preparedness.

CONCLUSIONS

Revision of a risk priority framework for category A bioterrorism agents shows that smallpox should be elevated in priority for preparedness planning, and that gene editing and synthetic biology raises the overall risk for all agents. The ranking of categories A, B, and C agents should also be revisited, as there is an endless possibility of engineered threats that may be more severe than any agent on the category A list.

Evidence for Residual Immunity to Smallpox After Vaccination and Implications for Re-emergence

INTRODUCTION

Smallpox has been eradicated but advances in synthetic biology have increased the risk of its re-emergence. Residual immunity in individuals who were previously vaccinated may mitigate the impact of an outbreak, but there is a high degree of uncertainty about the duration and degree of residual immunity. Both cell-mediated and humoral immunity are thought to be important but the exact mechanisms of protection are unclear. Guidelines usually suggest vaccine-induced immunity wanes to zero after 3-10 years post vaccination, whereas other estimates show long term immunity over decades.

MATERIALS AND METHODS

A systematic review of the literature was conducted to quantify the duration and extent of residual immunity to smallpox after vaccination.

RESULTS

Twenty-nine papers related to quantifying residual immunity to smallpox after vaccination were identified: neutralizing antibody levels were used as immune correlates of protection in 11/16 retrospective cross-sectional studies, 2/3 epidemiological studies, 6/7 prospective vaccine trials and 0/3 modeling studies. Duration of protection of >20 years was consistently shown in the 16 retrospective cross-sectional studies, while the lowest estimated duration of protection was 11.7 years among the modeling studies. Childhood vaccination conferred longer duration of protection than vaccination in adulthood, and multiple vaccinations did not appear to improve immunity.

CONCLUSIONS

Most studies suggest a longer duration of residual immunity (at least 20 years) than assumed in smallpox guidelines. Estimates from modeling studies were less but still greater than the 3-10 years suggested by the WHO Committee on International Quarantine or US CDC guidelines. These recommendations were probably based on observations and studies conducted while smallpox was endemic. The cut-off values for pre-existing antibody levels of >1:20 and >1:32 reported during the period of endemic smallpox circulation may not be relevant to the contemporary population, but have been used as a threshold for identifying people with residual immunity in post-eradication era studies. Of the total antibodies produced in response to smallpox vaccination, neutralizing antibodies have shown to contribute significantly to immunological memory. Although the mechanism of immunological memory and boosting is unclear, revaccination is likely to result in a more robust response. There is a need to improve the evidence base for estimates on residual immunity to better inform planning and preparedness for re-emergent smallpox.

Serological Immunity to Smallpox in New South Wales, Australia

The re-emergence of smallpox is an increasing and legitimate concern due to advances in synthetic biology. Vaccination programs against smallpox using the vaccinia virus vaccine ceased with the eradication of smallpox and, unlike many other countries, Australia did not use mass vaccinations. However, vaccinated migrants contribute to population immunity. Testing for vaccinia antibodies is not routinely performed in Australia, and few opportunities exist to estimate the level of residual population immunity against smallpox. Serological data on population immunity in Australia could inform management plans against a smallpox outbreak. Vaccinia antibodies were measured in 2003 in regular plasmapheresis donors at the Australian Red Cross Blood Service from New South Wales (NSW). The data were analysed to estimate the proportion of Australians in NSW with detectable serological immunity to vaccinia. The primary object of this study was to measure neutralising antibody titres against vaccinia virus. Titre levels in donor samples were determined by plaque reduction assay. To estimate current levels of immunity to smallpox infection, the decline in geometric mean titres (GMT) over time was projected using two values for the antibody levels estimated on the basis of different times since vaccination. The results of this study suggest that there is minimal residual immunity to the vaccinia virus in the Australian population. Although humoral immunity is protective against orthopoxvirus infections, cell-mediated immunity and immunological memory likely also play roles, which are not quantified by antibody levels. These data provide an immunological snapshot of the NSW population, which could inform emergency preparedness planning and outbreak control, especially concerning the stockpiling of vaccinia vaccine.

Public awareness, acceptability and risk perception about infectious diseases dual-use research of concern: a cross-sectional survey

OBJECTIVES

In this study, we aimed to measure the awareness, acceptability and perceptions of current issues in biosecurity posed by infectious diseases dual-use research of concern (DURC) in the community. DURC is conducted today in many locations around the world for the benefit of humanity but may also cause harm through either a laboratory accident or deliberate misuse. Most DURC is approved by animal ethics committees, which do not typically consider harm to humans. Given the unique characteristics of contagion and the potential for epidemics and pandemics, the community is an important stakeholder in DURC.

DESIGN

Self-administered web-based cross-sectional survey.

PARTICIPANTS

Participants over the age of 18 in Australia and 21 in the USA were included in the survey. A total of 604 participants completed the study. The results of 52 participants were excluded due to potential biases about DURC stemming from their employment as medical researchers, infectious diseases researchers or law enforcement professionals, leaving 552 participants. Of those, 274 respondents resided in Australia and 278 in the USA.

OUTCOMES

Baseline awareness, acceptability and perceptions of current issues surrounding DURC. Changes in perception from baseline were measured after provision of information about DURC.

RESULTS

Presurvey, 77% of respondents were unaware of DURC and 64% found it unacceptable or were unsure. Two-thirds of respondents did not change their views. The baseline perception of high risk for laboratory accidents (29%) and deliberate bioterrorism (34%) was low but increased with increasing provision of information (42% and 44% respectively, p<0.001), with men more accepting of DURC (OR=1.79, 95% CI 1.25 to 2.57, p=0.002). Postsurvey, higher education predicted lower risk perception of laboratory accidents (OR=0.56, 95% CI 0.34 to 0.93, p=0.02) and bioterrorism (OR=0.48, 95% CI 0.29 to 0.80, p=0.004).

CONCLUSION

The community is an important stakeholder in infectious diseases DURC but has a low awareness of this kind of research. Only a minority support DURC, and this proportion decreased with increasing provision of knowledge. There were differences of opinion between age groups, gender and education levels. The community should be informed and engaged in decisions about DURC.

Health system capacity in Sydney, Australia in the event of a biological attack with smallpox

Planning for a re-emergent epidemic of smallpox requires surge capacity of space, resources and personnel within health systems. There are many uncertainties in such a scenario, including likelihood and size of an attack, speed of response and health system capacity. We used a model for smallpox transmission to determine requirements for hospital beds, contact tracing and health workers (HCWs) in Sydney, Australia, during a modelled epidemic of smallpox. Sensitivity analysis was done on attack size, speed of response and proportion of case isolation and contact tracing. We estimated 100638 clinical HCWs and 14595 public hospital beds in Sydney. Rapid response, case isolation and contact tracing are influential on epidemic size, with case isolation more influential than contact tracing. With 95% of cases isolated, outbreak control can be achieved within 100 days even with only 50% of contacts traced. However, if case isolation and contact tracing both fall to 50%, epidemic control is lost. With a smaller initial attack and a response commencing 20 days after the attack, health system impacts are modest. The requirement for hospital beds will vary from up to 4% to 100% of all available beds in best and worst case scenarios. If the response is delayed, or if the attack infects 10000 people, all available beds will be exceeded within 40 days, with corresponding surge requirements for clinical health care workers (HCWs). We estimated there are 330 public health workers in Sydney with up to 940,350 contacts to be traced. At least 3 million respirators will be needed for the first 100 days. To ensure adequate health system capacity, rapid response, high rates of case isolation, excellent contact tracing and vaccination, and protection of HCWs should be a priority. Surge capacity must be planned. Failures in any of these could cause health system failure, with inadequate beds, quarantine spaces, personnel, PPE and inability to manage other acute health conditions.

Bayesian Phylogeography and Pathogenic Characterization of Smallpox Based on HA, ATI, and CrmB Genes

Variola virus is at risk of re-emergence either through accidental release, bioterrorism, or synthetic biology. The use of phylogenetics and phylogeography to support epidemic field response is expected to grow as sequencing technology becomes miniaturized, cheap, and ubiquitous. In this study, we aimed to explore the use of common VARV diagnostic targets hemagglutinin (HA), cytokine response modifier B (CrmB), and A-type inclusion protein (ATI) for phylogenetic characterization as well as the representativeness of modelling strategies in phylogeography to support epidemic response should smallpox re-emerge. We used Bayesian discrete-trait phylogeography using the most complete data set currently available of whole genome (n = 51) and partially sequenced (n = 20) VARV isolates. We show that multilocus models combining HA, ATI, and CrmB genes may represent a useful heuristic to differentiate between VARV Major and subclades of VARV Minor which have been associated with variable case-fatality rates. Where whole genome sequencing is unavailable, phylogeography models of HA, ATI, and CrmB may provide preliminary but uncertain estimates of transmission, while supplementing whole genome models with additional isolates sequenced only for HA can improve sample representativeness, maintaining similar support for transmission relative to whole genome models. We have also provided empirical evidence delineating historic international VARV transmission using phylogeography. Due to the persistent threat of re-emergence, our results provide important research for smallpox epidemic preparedness in the posteradication era as recommended by the World Health Organisation.

Confronting the threat of bioterrorism: realities, challenges, and defensive strategies

Global terrorism is a rapidly growing threat to world security, and increases the risk of bioterrorism. In this Review, we discuss the potential threat of bioterrorism, agents that could be exploited, and recent developments in technologies and policy for detecting and controlling epidemics that have been initiated intentionally. The local and international response to infectious disease epidemics, such as the severe acute respiratory syndrome and west African Ebola virus epidemic, revealed serious shortcomings which bioterrorists might exploit when intentionally initiating an epidemic. Development of new vaccines and antimicrobial therapies remains a priority, including the need to expedite clinical trials using new methodologies. Better means to protect health-care workers operating in dangerous environments are also needed, particularly in areas with poor infrastructure. New and improved approaches should be developed for surveillance, early detection, response, effective isolation of patients, control of the movement of potentially infected people, and risk communication. Access to dangerous pathogens should be appropriately regulated, without reducing progress in the development of countermeasures. We conclude that preparedness for intentional outbreaks has the important added value of strengthening preparedness for natural epidemics, and vice versa.