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The family contains 22 recognized virus species, each of them strongly associated with a rodent species (except Tacaribe virus which is associated with a species of bat), suggesting an ancient co-evolutionary process. Although the concept of co-evolution between rodents and arenaviruses is now largely accepted, little has been uncovered in terms of dating the phenomenon and the mechanisms of evolution, including speciation and pathogenicity. These questions are targeted in the present chapter. Old World arenaviruses are associated with the Eurasian rodents in the family Muridae. New World arenaviruses are associated with American rodents in the subfamily Sigmodontinae. The correlation between the rodent host phylogeny and the viruses suggests a long association and a co-evolutionary process. Furthermore, three distinct New World arenaviruses share a common ancestor, demonstrating a unique recombination event that probably occurred in that ancestor. This shows that recombination among arenaviruses of different lineages might occur in nature. Recombination and co-evolutionary adaptation appear as the main mechanisms of arenavirus evolution, generating a high degree of diversity. The diversity among rodent host reservoir and virus species and the potential to exchange genomic material provide a basis for the emergence of new viruses and the risk of these becoming pathogenic for humans.

Two infectious diseases, and one presumably infectious disease, each vectored by or associated with the bite of the lone star tick ( ), were identified and characterized by clinicians and scientists in the United States during the 1980s and 1990s. These three conditions—human monocytic (or monocytotropic) ehrlichiosis (HME), ehrlichiosis, and southern tick-associated rash illness (STARI)—undoubtedly existed in the United States prior to this time. However, the near-simultaneous recognition of these diseases is remarkable and suggests the involvement of a unifying process that thrust multiple pathogens into the sphere of human recognition.

Severe acute respiratory syndrome (SARS) was the first pandemic transmissible disease of previously unknown aetiology in the twenty-first century. Early epidemiologic investigations suggested an animal origin for SARS-CoV. Virological and serological studies indicated that masked palm civets ( ), together with two other wildlife animals, sampled from a live animal market were infected with SARS-CoV or a closely related virus. Recently, horseshoe bats in the genus have been identified as natural reservoir of SARS-like coronaviruses. Here, we review studies by different groups demonstrating that SARS-CoV succeeded in spillover from a wildlife reservoir (probably bats) to human population via an intermediate host(s) and that rapid virus evolution played a key role in the adaptation of SARS-CoVs in at least two nonreservoir species within a short period.

Poxviruses are famous, or infamous, as agents of disease introduced into novel host species and between populations of the same species. This discussion concerns selected examples of poxviruses associated with vertebrate infections, i.e., the Chordopoxvirus subfamily of the family Poxviridae. Brief note is made of examples of members of the genera and -like agents that have been recognized to have significant trans-host species impact. The remaining bulk of the discussion involves examples of members of the genus , which are known to be (have been) involved with human disease, and their zoonotic origins.

Since Ebola fever emerged in Central Africa in 1976, a number of studies have been undertaken to investigate its natural history and to characterize its transmission from a hypothetical reservoir host(s) to humans. This research has comprised investigations on a variety of animals and their characterization as intermediate, incidental, amplifying, reservoir, or vector hosts. A viral transmission chain was recently unveiled after a long absence of epidemic Ebola fever. Animal trapping missions were carried out in the Central African rain forest in an area where several epidemics and epizootics had occurred between 2001 and 2005. Among the various animals captured and analyzed, three species of fruit bats (suborder Megachiroptera) were found asymptomatically and naturally infected with Ebola virus: (hammer-headed fruit beats), (singing fruit bats), and (little collared fruit bats).

The uneven standards of surveillance, human- or animal-based, for zoonotic diseases or pathogens maintained and transmitted by wildlife H R s, or even domestic species, is a global problem, readily apparent even within the United States, where investment in public health, including surveillance systems, has a long and enviable history. As of 2006, there appears to be little scientific, social, or political consensus that animalbased surveillance for zoonoses merits investment in international infrastructure, other than the fledgling efforts with avian influenza, or targeted nontraditional avenues of surveillance and research.

There is a recognized need for increased wildlife disease surveillance and research related to understanding the epidemiology and control of emerging wildlife and zoonotic diseases. Although both passive and active surveillance strategies can and have been effectively used with wildlife, some unique problems are often encountered. These can include limitations related to case acquisition and under-reporting, difficulty in designing sampling strategies that adequately represent the population of interest, the lack of properly validated diagnostic tests, problems related to data interpretation due to missing or inaccurate denominator data, and the lack of an existing wildlife surveillance infrastructure. Many of these same problems are often encountered in field research, which can be further complicated by the complexity and scale of the natural systems in which this work takes place. Although such studies may be difficult, there are numerous examples of success and our understanding of wildlife and wildlife-related zoonotic and emerging disease continues to grow.

Emerging infectious diseases are a key threat to public health and the majority are caused by zoonotic pathogens. Here we discuss new collaborative approaches to understanding the process of zoonotic disease emergence that link veterinary medicine, public health, and ecological approaches: conservation medicine and one health. We demonstrate how studies on the underlying drivers of disease emergence (bushmeat hunting, wildlife trade, and deforestation) can provide ways to model, predict, and ultimately prevent zoonotic disease emergence and spread.

New and emerging infectious diseases affect humans, domestic animals, livestock and wildlife and can have a significant impact on health, trade and biodiversity. Of the emerging infectious diseases of humans, 75% are zoonotic, with wildlife being an increasingly important source of inter-species transmission. Recent animal health emergencies have highlighted the vulnerability of the livestock sector to the impact of infectious diseases and the associated risks to human health. Outbreaks resulting from wildlife trade have resulted in enormous economic losses globally. On a global level, the human health sector lags behind the animal health sector in the assessment of potential threats, although substantive differences exist among countries in the state of national preparedness planning for emerging diseases.