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[Emerging viral diseases].

Emerging and re-emerging infectious diseases have again entered the public arena in recent years. This is due to factors such as evolving lifestyles, ecological and socio-political upheavals, and recent diagnostic advances. Numerous pathogens, including viruses like West Nile, Chikungunya and Japanese encephalitis on the one hand, and hemorrhagic fever viruses like Ebola and Maburg, are particular concerns. Recently, the Corona virus responsible for SARS, which caused an epidemic sufficiently worrisome to challenge crisis management concepts, was successfully isolated. It is in this context that so-called "bird flu'", may be on the verge of causing a human pandemic. Pox and Monkeypox are "virtually emerging" viruses that have potential for use in bioterrorism. The management and treatment of these emerging infectious diseases calls for new approaches, organizations and infrastructures.

Animals↗

[Possible mechanism of orthopoxvirus preservation in nature].

Until recently, virus carrier state in the absence of overt clinical infection has been known for only one species of orthopoxviruses, namely, ectromelia virus. The paper describes the results of the modelling of asypmtomatic infection caused by monkeypox, cowpox, and ratpox viruses. Persistence of these viruses up to 6 weeks in animals (hamsters, cotton and white rats) with experimental asymptomatic infection as well as in apparently normal naturally infected white rats was established by isolation of virus from the organs of these animals. These results suggest that asymptomatic virus carrier state may occur both with ectromelia and a number of other orthopoxviruses. The mechanism may be of ecological importance, providing for circulation of these viruses and their preservation as biological species in nature.

Animals↗

[Biohazards due to Orthopoxvirus: should we re-vaccinate against smallpox?].

Although the WHO declared global smallpox eradication in 1980, the Orthopoxvirus remains a source of concern for several reasons. Firstly, stocks of the smallpox virus have been preserved for experimental use (at least officially in the USA and Russia) so that an escaped isolate could lead to reemergence and spread of the disease worldwide. Secondly discontinuation of smallpox vaccination programs has led to dwindling acquired immunity in the world population thus raising the risk of epidemic extension of several Orthopoxvirus zoonoses (e.g., monkeypox). Thirdly stocks of camelpox virus which is very similar to Smallpox virus and was intended for biological warfare were discovered during the Gulf War in 1991 and pose a potentially serious threat. Finally official stocks of Smallpox virus could be stolen and used by bioterrorists. Thus reemergence of Orthopoxvirus including smallpox, monkeypox, cowpox, and camelpox is a real danger and contingency planning is needed to define prophylactic and therapeutic strategies to prevent and/or stop an epidemics. Adverse effects from earlier smallpox vaccine (vaccinia) in healthy people or immunocompromised people (congenital or acquired as in HIV infected patients) are absolute contraindications to smallpox vaccination at this time. Further research is needed to develop new vaccines (e.g., attenuated isolates of vaccinia) and effective treatment. This is the only valid reasons for postponing planned destruction of remaining Smallpox virus stocks.

Biological Warfare↗

Detection and differentiation of old world orthopoxviruses: restriction fragment length polymorphism of the crmB gene region.

A restriction fragment length polymorphism (RFLP) assay was developed to identify and differentiate Old World, African-Eurasian orthopoxviruses (OPV): variola, vaccinia, cowpox, monkeypox, camelpox, ectromelia, and taterapox viruses. The test uses amplicons produced from virus genome DNA by PCR with a consensus primer pair designed from sequences determined for the cytokine response modifier B (crmB) gene of 43 different OPV strains of known taxonomic origin. The primer pair amplified a single specific product from each of the 115 OPV samples tested. Size-specific amplicons identified and differentiated ectromelia and vaccinia virus strains, which contain a truncated crmB gene, and enabled their differentiation from other OPV species. Restriction digests of amplified products allowed the identification and differentiation of variola, monkeypox, camelpox, vaccinia, and cowpox virus species and strains.

Humans↗

Detection and discrimination of orthopoxviruses using microarrays of immobilized oligonucleotides.

Variola virus (VARV), causing smallpox, is a potential biological weapon. Methods to detect VARV rapidly and to differentiate it from other viruses causing similar clinical syndromes are needed urgently. We have developed a new microarray-based method that detects simultaneously and discriminates four orthopoxvirus (OPV) species pathogenic for humans (variola, monkeypox, cowpox, and vaccinia viruses) and distinguishes them from chickenpox virus (varicella-zoster virus or VZV). The OPV gene C23L/B29R, encoding the CC-chemokine binding protein, was sequenced for 41 strains of seven species of orthopox viruses obtained from different geographical regions. Those C23L/B29R sequences and the ORF 62 sequences from 13 strains of VZV (selected from GenBank) were used to design oligonucleotide probes that were immobilized on an aldehyde-coated glass surface (a total of 57 probes). The microchip contained several unique 13-21 bases long oligonucleotide probes specific to each virus species to ensure redundancy and robustness of the assay. A region approximately 1100 bases long was amplified from samples of viral DNA and fluorescently labeled with Cy5-modified dNTPs, and single-stranded DNA was prepared by strand separation. Hybridization was carried out under plastic coverslips, resulting in a fluorescent pattern that was quantified using a confocal laser scanner. 49 known and blinded samples of OPV DNA, representing different OPV species, and two VZV strains were tested. The oligonucleotide microarray hybridization technique identified reliably and correctly all samples. This new procedure takes only 3 h, and it can be used for parallel testing of multiple samples.

DNA Primers↗

[Monkey pox virus infection in humans in the Central African Republic].

A human monkeypox outbreak is reported which occurred in January 1984 in the extreme south-west areas of the Central African Republic. Six persons were found to be affected in a Pygmy camp with an estimated population of 50 residents. In the two affected families, out of 11 members, only unvaccinated children and a 22 year old unvaccinated woman contracted the disease. The disease was of moderate severity in two patients and very mild in the other four. The clinical diagnosis was confirmed by virus isolation from skin lesions of 4 patients and by sero-immunologic tests in all of them. The clinically apparent monkeypox case reported in the Central African Republic in 1983, the presently described outbreak, as well as information on the disease obtained from Pygmies and missionary paramedical staff who are in frequent contact with them, suggest that monkeypox is enzootic in the tropical rain forest in the south-west areas of the Central African Republic.

Central African Republic↗

Follow-up on diagnostic proficiency of laboratories equipped to perform orthopoxvirus detection and quantification by PCR: the second international external quality assurance study.

Two years after the first external quality assurance study on bioterrorism-relevant viruses, we have conducted a follow-up study on orthopoxvirus detection by PCR. Thirty-three laboratories (27 European, 4 Austral-Asian, and 2 American) participated. Samples contained 0 to 40,000,000 DNA copies of lyophilized monkeypox, cowpox, and vaccinia virus per ml. Laboratories achieved a >80% detection chance above 56,234 copies per ml. Global sensitivity was not significantly improved over that of the first study. Twenty-seven and 9 participants, respectively, were able to genotype and quantify virus. Four of 27 genotyping results were incorrect. Quantification accuracy was significantly better for vaccinia virus than for the other viruses. False-positive results occurred in 22 (11.8%) of all 186 tests on negative samples, but 18 of these were contributed by only five laboratories. Fifty-five percent of laboratories could appropriately detect PCR inhibition. The use of either real-time PCR or commercial diagnostic kits had significant positive influence on laboratory performance.

Clinical Laboratory Techniques↗

Amplification of 'variola virus-specific' sequences in German cowpox virus isolates.

In 1995 a polymerase chain reaction (PCR) protocol describing the specific detection of variola virus, the causative agent of smallpox, was published by Knight and others. Virulent variola major strains could be differentiated from less virulent variola minor strains because of the distinct amplicon sizes. Here, we applied this PCR protocol to DNA from various orthopoxvirus isolates. There was no amplification with the orthopoxvirus species vaccinia, monkeypox, mousepox, or camelpox viruses. However, amplification was observed in six out of 15 cowpox virus strains investigated. The size of the amplicons corresponded exactly with the size described for variola minor strains and the nucleotide sequence identity accounted for 97%. Findings are discussed with respect to the evolution of orthopoxvirus species assuming that variola virus most probably stems from a rodent-transmitted cowpox virus-like progenitor.

Animals↗

Poxvirus infection of the baboon (Papio cynocephalus).

Ten serial passages of monkeypox (MPV), vaccinia, variola, and chimpanzeepox (chimp-9) viruses were performed in baboons (Papio cynocephalus) via skin scarification. Comparisons of clinical and virological results indicate that MPV and vaccinia are very closely related and that variola and chimp-9 viruses are identical. These findings suggest that infections of simians with chimp-9 virus resulted from contact with variola virus, the source of which is still unknown. On the other hand, MPV in monkeys may have resulted from contact with recently vaccinated humans, serial passage through simian hosts resulting in the biological alterations that produced MPV.

Animals↗

Gene for A-type inclusion body protein is useful for a polymerase chain reaction assay to differentiate orthopoxviruses.

Orthopoxvirus species were identified and differentiated by polymerase chain reaction amplification of genome DNA using a single primer-pair based on sequences coding for the major protein component of the cowpox virus acidophilic-type inclusion body (ATI). DNA available for 6 of 8 Old World (cowpox, variola, monkeypox, camelpox, ectromelia and vaccinia viruses) and 3 New World (skunkpox, volepox, and raccoonpox) resulted in amplicons that ranged in size from 510 to 1673 base pairs depending on the species, except for raccoonpox virus DNA which did not amplify. XbaI digest gel electrophoresis profiles of the amplicons improved resolution of the differences.

Animals↗

Monkeypox: an epidemiologic and clinical comparison of African and US disease.

Monkeypox is a double-stranded DNA virus and a member of the genus Orthopoxvirus. Human monkeypox was first identified in the Democratic Republic of the Congo (formerly Zaire) in 1970. The first outbreak in the western hemisphere occurred in the spring of 2003. Important epidemiologic and clinical differences exist between human monkeypox in the United States and in Africa, including sex distribution, case fatality, morphology of skin lesions, and associated lymphadenopathy. These divergent clinical presentations could be caused by mode of transmission (skin inoculation vs ingestion), the skin color of affected patients, the training backgrounds of those who saw and documented disease outbreaks, the virulence of monkeypox strains involved, nutritional status, access to advanced medical care, and the prevalence of prior smallpox vaccinations.

Africa↗

Monkeypox-specific antibodies in human and simian sera from the Ivory Coast and Nigeria.

A test for monkeypox-specific antibodies is described. Monkeypox immune sera can be made type-specific by immunoabsorption with heterotypic poxvirus extracts. Monkeypox-specific antibodies were demonstrated in sera from 9 cynomolgus monkeys (Macaca fascicularis) that had previously been experimentally infected with monkeypox. Monkeypox-specific antibodies were found in 3 wild-caught African monkeys (Cercopithecus spp.) and in 3 human sera collected from Africans in the Ivory Coast and Nigeria 3(1/2)-4 years after they had suffered a pox-like infection. Monkeypox had been recognized in one of the patients by virus isolation, and had been suspected in the others for epidemiological reasons. Vaccinia-specific antibodies were found in 4 human sera collected 6 weeks after smallpox vaccination.The serological results provide the first laboratory evidence of a monkeypox reservoir in wild monkeys.

Animals↗

[Immunomodulatory proteins of orthopoxviruses].

The review considers recent data on the structural-functional organization of the genome of orthopoxviruses pathogenic for humans, including the variola, monkeypox, cowpox, and vaccinia viruses. Emphasis was placed on the structure of molecular virulence factors that suppress the inflammatory reactions, immune response, and interferon effects induced by virus infection.

Amino Acid Sequence↗

Monkeypoxvirus infections.

During and after the smallpox eradication campaign, human cases of monkeypox appeared in West and Central Africa, as isolated cases or as small epidemics. Since inter-human transmission has never or only very exceptionally been documented, monkeypox does not represent a serious threat to humans. The virus reservoir is among tree squirrels living in the tropical rain forests of Africa and humans are infected by hunting, killing and skinning these animals. However, the modernization of society lessens human contact with the virus reservoir. Since the eradication of smallpox, stocks of variola virus have been maintained; whether these stocks should now be destroyed is a political question, which is seriously compromised by mistrust between countries.

Animals↗

Smallpox and monkeypox in non-human primates.

In considering global eradication of smallpox the absence of an animal reservoir is important. Present knowledge of experimental infection of non-human primates with variola virus and of a related virus infection in monkeys, termed monkeypox, is examined.From the literature review and the results of a survey of captive monkeys in 26 major biological institutions it is concluded that outbreaks of supposed smallpox and monkeypox are not frequent and that man may be comparatively insusceptible to monkeypox. A natural reservoir of smallpox in non-human primates is thought to be unlikely although further studies are warranted since the survey reveals that certain species of monkeys can be infected with smallpox and that infected monkeys can transmit infection to others.

Animals↗

PCR strategy for identification and differentiation of small pox and other orthopoxviruses.

Rapid identification and differentiation of orthopoxviruses by PCR were achieved with primers based on genome sequences encoding the hemagglutinin (HA) protein, an infected-cell membrane antigen that distinguishes orthopoxviruses from other poxvirus genera. The initial identification step used a primer pair of consensus sequences for amplifying an HA DNA fragment from the three known North American orthopoxviruses (raccoonpox, skunkpox, and volepox viruses), and a second pair for amplifying virtually the entire HA open reading frame of the Eurasian-African orthopoxviruses (variola, vaccinia, cowpox, monkeypox, camelpox, ectromelia, and gerbilpox viruses). RsaI digest electropherograms of the amplified DNAs of the former subgroup provided species differentiation, and TaqI digests differentiated the Eurasian-African orthopoxviruses, including vaccinia virus from the vaccinia virus subspecies buffalopox virus. Endonuclease HhaI digest patterns distinguished smallpox variola major viruses from alastrim variola minor viruses. For the Eurasian-African orthopoxviruses, a confirmatory step that used a set of higher-sequence-homology primers was developed to provide sensitivity to discern individual virus HA DNAs from cross-contaminated orthopoxvirus DNA samples; TaqI and HhaI digestions of the individual amplified HA DNAs confirmed virus identity. Finally, a set of primers and modified PCR conditions were developed on the basis of base sequence differences within the HA genes of the 10 species, which enabled production of a single DNA fragment of a particular size that indicated the specific species.

Animals↗

[Tenth anniversary of smallpox eradication: Results of epidemiological and virological surveillance and studies in the post-eradication period].

In accordance with recommendations of the Global Commission on the certification of smallpox eradication for the 10-year period after the eradication of this infection, all suspected cases of smallpox have been thoroughly checked up, and in none of them the diagnosis of smallpox has been confirmed. The study of monkeypox in humans has revealed that this zoonosis is spread over a wider area than supposed earlier and covers 7 countries of Equatorial Africa, occurring most frequently in Zaire. In about 70% of cases of monkeypox in human the disease is contracted from animals serving as natural virus carriers and in about one-third of such cases, from humans having monkeypox. The infectivity of humans with monkeypox for persons having close contacts with them is somewhat lower (12.3%) than in smallpox when this characteristic varies from 37% to 88%. Monkeypox in humans may take an asymptomatic course. Some species of tropical squirrels serve as natural virus carriers. These investigations have also resulted in essential corrections being made in understanding the ecology of cowpox virus, another orthopoxvirus pathogenic for man. At least 5 species of rodents have proved to be of interest as natural carriers of cowpox virus.

Africa↗