Clinical manifestations of human monkeypox influenced by route of infection

Clinical experience, infection control practices and diagnostic algorithms for poxvirus infections - an Emerging Infections Network survey

Background

In order to determine how best to tailor outreach messages about poxvirus diagnosis and infection control for health practitioners, we surveyed infectious disease physicians in the Infectious Diseases Society of America's Emerging Infections Network.

Findings

Surveys consisting of two unknown case scenarios designed to raise suspicion for monkeypox and orf were distributed to the 1,080 members of the EIN. The surveys contained questions pertaining to which diagnostic tests, points of contact, and transmission precautions they would likely utilize during patient evaluation. Basic response rates and frequencies of responses were calculated. Comparisons of the survey responses were made using the chi-square test. Of the 212 members who responded (20% response rate), significantly more respondents indicated that they would request diagnostic testing in the context of the monkeypox case scenario as compared to the orf case scenario. A significantly higher number of respondents indicated they would institute droplet or airborne precautions for the monkeypox case as opposed to the orf case scenario.

Conclusions

This survey provided an opportunity for public health practitioners to gain insight into physician approaches to evaluation, diagnosis and reporting of suspected poxvirus-associated infections. This survey identified key areas in which public health practitioners can better serve physicians by focusing on education. As a result we were able to identify potential knowledge gaps and deficits in the availability of useful resources to facilitate accurate case identification and management.

Comparison of West African and Congo Basin monkeypox viruses in BALB/c and C57BL/6 mice

Although monkeypox virus (MPXV) studies in wild rodents and non-human primates have generated important knowledge regarding MPXV pathogenesis and inferences about disease transmission, it might be easier to dissect the importance of virulence factors and correlates of protection to MPXV in an inbred mouse model. Herein, we compared the two clades of MPXV via two routes of infection in the BALB/c and C57BL/6 inbred mice strains. Our studies show that similar to previous animal studies, the Congo Basin strain of MPXV was more virulent than West African MPXV in both mouse strains as evidenced by clinical signs. Although animals did not develop lesions as seen in human MPX infections, localized signs were apparent with the foot pad route of inoculation, primarily in the form of edema at the site of inoculation; while the Congo Basin intranasal route of infection led to generalized symptoms, primarily weight loss. We have determined that future studies with MPXV and laboratory mice would be very beneficial in understanding the pathogenesis of MPXV, in particular if used in in vivo imaging studies. Although this mouse model may not suffice as a model of human MPX disease, with an appropriate inbred mouse model, we can unravel many unknown aspects of MPX pathogenesis, including virulence factors, disease progression in rodent hosts, and viral shedding from infected animals. In addition, such a model can be utilized to test antivirals and the next generation of orthopoxvirus vaccines for their ability to alter the course of disease.

One more piece in the VACV ecological puzzle: could peridomestic rodents be the link between wildlife and bovine vaccinia outbreaks in Brazil?

Background

Despite the fact that smallpox eradication was declared by the World Health Organization (WHO) in 1980, other poxviruses have emerged and re-emerged, with significant public health and economic impacts. Vaccinia virus (VACV), a poxvirus used during the WHO smallpox vaccination campaign, has been involved in zoonotic infections in Brazilian rural areas (Bovine Vaccinia outbreaks – BV), affecting dairy cattle and milkers. Little is known about VACV's natural hosts and its epidemiological and ecological characteristics. Although VACV was isolated and/or serologically detected in Brazilian wild animals, the link between wildlife and farms has not yet been elucidated.

Methodology/Principal Findings

In this study, we describe for the first time, to our knowledge, the isolation of a VACV (Mariana virus - MARV) from a mouse during a BV outbreak. Genetic data, in association with biological assays, showed that this isolate was the same etiological agent causing exanthematic lesions observed in the cattle and human inhabitants of a particular BV-affected area. Phylogenetic analysis grouped MARV with other VACV isolated during BV outbreaks.

Conclusion/Significance

These data provide new biological and epidemiological information on VACV and lead to an interesting question: could peridomestic rodents be the link between wildlife and BV outbreaks?

Emerging viral infections of the central nervous system: part 2

The first part of this review ended with a discussion of new niches for known viruses as illustrated by viral central nervous system (CNS) disease associated with organ transplant and the syndrome of human herpesvirus 6-associated posttransplant acute limbic encephalitis. In this part, we begin with a continuation of this theme, reviewing the association of JC virus-associated progressive multifocal leukoencephalopathy (PML) with novel immunomodulatory agents. This part then continues with emerging viral infections associated with importation of infected animals (monkeypox virus), then spread of vectors and enhanced vector competence (chikungunya virus [CHIK]), and novel viruses causing CNS infections including Nipah and Hendra viruses and bat lyssaviruses (BLV).

Comparison of monkeypox viruses pathogenesis in mice by in vivo imaging

Monkeypox viruses (MPXV) cause human monkeypox, a zoonotic smallpox-like disease endemic to Africa, and are of worldwide public health and biodefense concern. Using viruses from the Congo (MPXV-2003-Congo-358) and West African (MPXV-2003-USA-044) clades, we constructed recombinant viruses that express the luciferase gene (MPXV-Congo/Luc+and MPXV-USA-Luc+) and compared their viral infection in mice by biophotonic imaging. BALB/c mice became infected by both MPXV clades, but they recovered and cleared the infection within 10 days post-infection (PI). However, infection in severe combined immune deficient (SCID) BALB/c mice resulted in 100% lethality. Intraperitoneal (IP) injection of both MPXV-Congo and MPXV-Congo/Luc+resulted in a systemic clinical disease and the same mean time-to-death at 9 (±0) days post-infection. Likewise, IP injection of SCID-BALB/c mice with MPXV-USA or the MPXV-USA-Luc+, resulted in similar disease but longer (P<0.05) mean time-to-death (11±0 days) for both viruses compared to the Congo strains. Imaging studies in SCID mice showed luminescence in the abdomen within 24 hours PI with subsequent spread elsewhere. Animals infected with the MPXV-USA/Luc+had less intense luminescence in tissues than those inoculated with MPXV-Congo/Luc+, and systemic spread of the MPXV-USA/Luc+virus occurred approximately two days later than the MPXV-Congo/Luc+. The ovary was an important target for viral replication as evidenced by the high viral titers and immunohistochemistry. These studies demonstrate the suitability of a mouse model and biophotonic imaging to compare the disease progression and tissue tropism of MPX viruses.

Cowpox virus transmission from pet rats to humans, Germany

We describe a cluster of cowpox virus (CPXV) infections in humans that occurred near Munich, Germany, around the beginning of 2009. Previously, only sporadic reports of CPXV infections in humans after direct contact with various animals had been published. This outbreak involved pet rats from the same litter.

A prairie dog animal model of systemic orthopoxvirus disease using West African and Congo Basin strains of monkeypox virus

Multiple monkeypox virus (MPXV) animal models have been discussed in previous studies, but no small animal models, nor most non-human primate models, demonstrated the protracted asymptomatic incubation phase seen in systemic human orthopoxvirus illness. Herein, we characterize a black-tailed prairie dog (PD) (Cynomys ludovicianus) model of infection, via intranasal and intradermal exposures, with the two MPXV clades. Daily observations of the animals were made (food consumption, general symptoms, disease presentation), while weights and virus evaluations (ocular, nasal, oropharyngeal, faeces, blood) were obtained/made every third day. Generalized rash became apparent 9-12 days post-infection for all animals. Individual animals demonstrated a range of symptoms consistent with human monkeypox disease. Measurable viraemias and excretas were similar for both clade-representative strains and persisted until at least day 21. Greater morbidity was observed in Congo Basin strain-challenged animals and mortality was observed only in the Congo Basin strain-challenged animals. The PD model is valuable for the study of strain-dependent differences in MPXV. Additionally, the model closely mimics human systemic orthopoxvirus disease and may serve as a valuable non-human surrogate for investigations of antivirals and next generation orthopoxvirus vaccines.

[Human monkeypox]

Unlike other recent viral emergences, which were in majority caused by RNA viruses, the monkeypox results from infection by a DNA virus, an orthopoxvirus closely related to both vaccine and smallpox viruses and whose two genomic variants are known. Unexpectedly isolated from captive Asiatic monkeys and first considered as an laboratory curiosity, this virus was recognised in 1970 as an human pathogen in tropical Africa. Here it was responsible for sporadic cases following intrusions (for hunting) into tropical rain forests or rare outbreak with human-to-human transmission as observed in 1996 in Democratic Republic of Congo. As monkeypox in humans is not distinguishable from smallpox (a disease globally eradicated in 1977) it was only subjected to vigilant epidemiological surveillance and not considered as a potential threat outside Africa. This point of view radically changed in 2003 when monkeypox was introduced in the USA by African wild rodents and spread to 11 different states of this country. Responsible for 82 infections in American children and adults, this outbreak led to realize the sanitary hazards resulting from international trade of exotic animals and scientific investigations increasing extensively our knowledge of this zoonosis.

Natural human infections with Vaccinia virus during bovine vaccinia outbreaks

BACKGROUND

Bovine vaccinia is an exanthematic disease caused by Vaccinia virus (VACV). This zoonosis has been associated with several cases of bovine infection, particularly in milk herds. Farmers, milkers and their close contacts developed lesions on the hands, forearms, legs and face accompanied by fever, headache, malaise, myalgia and axillary, inguinal and cervical lymphadenopathy. VACV infections have a significant public health impact due to their occupational character, high frequency of transmission and the improper medical treatment often applied.

OBJECTIVES

To study natural human infection by VACV and to analyze clinical and epidemiological aspects, emphasizing the patients' immunological status.

STUDY DESIGN

Ninety-eight individuals from rural properties with bovine vaccinia (BV) outbreaks who were at risk due to contact were submitted to epidemiological and clinical studies. From these individuals, 54 sera were analyzed by serological and molecular procedures. This study was conducted in Rio de Janeiro State from September 2002 to October 2006.

RESULTS

The clinical frequency of infection was 52.0%, with 57.4% ELISA and 43.0% PRNT-positive reactions. DNAemia was detected in 18.5% of the analyzed sera, and 50% of smallpox-vaccinated individuals developed symptoms.

CONCLUSIONS

This study confirms the high clinical frequency of human VACV infection, even among vaccinated individuals. The infection was related to detection of IgG- or IgM-specific antibodies that correlates in most of the cases with positive PRNT. The DNAemia suggests viremia during VACV natural infections. Our data indicate that patients vaccinated against smallpox may no longer be protected.

Transmission of atypical varicella-zoster virus infections involving palm and sole manifestations in an area with monkeypox endemicity

During a suspected monkeypox outbreak in the Republic of Congo, we documented transmission of varicella-zoster virus (VZV) infection with palm and sole manifestations among 5 family members. Genotyping results confirmed the VZV strain European E2, a genotype not previously reported in Africa. VZV with palm and sole involvement should be considered when differentiating a monkeypox diagnosis.

Vaccinia virus: shedding and horizontal transmission in a murine model

Vaccinia virus (VACV) has been associated with several bovine vaccinia outbreaks in Brazil, affecting cattle and humans. There are no available data about VACV environmental circulation or the role of wildlife in the emergence of an outbreak. Since VACV was isolated from rodents in Brazil, we investigated shedding and transmission of VACV strains in mice. The VACV excretion profile was assessed by PCR and chicken chorioallantoic membrane infection, revealing viral DNA and infectious virus in the faeces and urine of intranasally infected mice. Horizontal transmission was assessed by exposure of sentinel mice to wood shavings contaminated with excrement, to mimic a natural infection. Sentinel mice showed orthopoxvirus antibodies, and VACV DNA and infectious virus were detected in their faeces and intestines, even after six rounds of natural transmission. Together, these data suggest that murine excrement could play a relevant role in VACV spread and transmission, perhaps helping to explain how these viruses circulate between their natural hosts.

Eczema vaccinatum resulting from the transmission of vaccinia virus from a smallpox vaccinee: an investigation of potential fomites in the home environment

On March 3, 2007, a 2-year-old boy was hospitalized with eczema vaccinatum. His two siblings, one with eczema, were subsequently removed from the home. Swabs of household items obtained on March 13th were analyzed for orthopoxvirus DNA signatures with real-time PCR. Virus culture was attempted on positive specimens. Eight of 25 household samples were positive by PCR for orthopoxvirus; of these, three yielded viable vaccinia virus in culture. Both siblings were found to have serologic evidence of orthopoxvirus exposure. These findings have implications for smallpox preparedness, especially in situations where some household members are not candidates for vaccination.

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.

Monkeypox-induced immunity and failure of childhood smallpox vaccination to provide complete protection

Following the U.S. monkeypox outbreak of 2003, blood specimens and clinical and epidemiologic data were collected from cases, defined by standard definition, and household contacts of cases to evaluate the role of preexisting (smallpox vaccine-derived) and acquired immunity in susceptibility to monkeypox disease and clinical outcomes. Orthopoxvirus-specific immunoglobulin G (IgG), IgM, CD4, CD8, and B-cell responses were measured at approximately 7 to 14 weeks and 1 year postexposure. Associations between immune responses, smallpox vaccination, and epidemiologic and clinical data were assessed. Participants were categorized into four groups: (i) vaccinated cases, (ii) unvaccinated cases, (iii) vaccinated contacts, and (iv) unvaccinated contacts. Cases, regardless of vaccination status, were positive for orthopoxvirus-specific IgM, IgG, CD4, CD8, and B-cell responses. Antiorthopoxvirus immune responses consistent with infection were observed in some contacts who did not develop monkeypox. Vaccinated contacts maintained low levels of antiorthopoxvirus IgG, CD4, and B-cell responses, with most lacking IgM or CD8 responses. Preexisting immunity, assessed by high antiorthopoxvirus IgG levels and childhood smallpox vaccination, was associated (in a nonsignificant manner) with mild disease. Vaccination failed to provide complete protection against human monkeypox. Previously vaccinated monkeypox cases manifested antiorthopoxvirus IgM and changes in antiorthopoxvirus IgG, CD4, CD8, or B-cell responses as markers of recent infection. Antiorthopoxvirus IgM and CD8 responses occurred most frequently in monkeypox cases (vaccinated and unvaccinated), with IgG, CD4, and memory B-cell responses indicative of vaccine-derived immunity. Immune markers provided evidence of asymptomatic infections in some vaccinated, as well as unvaccinated, individuals.

Spectrum of infection and risk factors for human monkeypox, United States, 2003

For the 2003 monkeypox virus (MPXV) outbreak in the United States, interhuman transmission was not documented and all case-patients were near or handled MPXV-infected prairie dogs. We initiated a case-control study to evaluate risk factors for animal-to-human MPXV transmission. Participants completed a questionnaire requesting exposure, clinical, and demographic information. Serum samples were obtained for analysis of immunoglobulin G (IgG) and IgM to orthopoxvirus. When data were adjusted for smallpox vaccination, case-patients were more likely than controls to have had daily exposure to a sick animal (odds ratio [OR] 4.0, 95% confidence interval [CI] 1.2-13.4), cleaned cages and bedding of a sick animal (OR 5.3, 95% CI 1.4-20.7), or touched a sick animal (OR 4.0, 95% CI 1.2-13.4). These findings demonstrate that human MPXV infection is associated with handling of MPXV-infected animals and suggest that exposure to excretions and secretions of infected animals can result in infection.

Human monkeypox: an emerging zoonotic disease

Zoonotic monkeypox virus is maintained in a large number of rodent and, to a lesser extent, nonhuman primate species in West and central Africa. Although monkeypox virus was discovered in 1958, the prototypic human cases were not witnessed until the early 1970s. Before this time, it is assumed that infections were masked by smallpox, which was then widely endemic. Nevertheless, since the 1970s, reported monkeypox virus infections of humans have escalated, as have outbreaks with reported human-to-human transmission. This increase is likely due to numerous factors, such as enhanced surveillance efforts, environmental degradation and human urbanization of areas where monkeypox virus is maintained in its animal reservoir(s) and, consequently, serve as a nidus for human infection. Furthermore, viral genetic predispositions enable monkeypox virus to infect many animal species, represented in expansive geographic ranges. Monkeypox virus was once restricted to specific regions of Africa, but its environ has expanded, in one case intercontinentally--suggesting that human monkeypox infections could continue to intensify. As a zoonotic agent, monkeypox virus is far less sensitive to typical eradication measures since it is maintained in wild-animal populations. Moreover, human vaccination is becoming a less viable option to control poxvirus infections in today's increasingly immunocompromised population, particularly with the emergence of HIV in Sub-Saharan Africa. An increased frequency of human monkeypox virus infections, especially in immunocompromised individuals, may permit monkeypox virus to evolve and maintain itself independently in human populations.