ویروس های بیماری زا
Abstract
1- Emergence of viral diseases
2- Molecular biology of pathogenic viruses
3- Polymerase chain reaction
4- DNA sequencing
5- Development of laboratory capacity
6- Conclusion
Acknowledgements
References
Abstract
Pathogenic viruses are viruses that can infect and replicate within human cells and cause diseases. The continuous emergence and re-emergence of pathogenic viruses has become a major threat to public health. Whenever pathogenic viruses emerge, their rapid detection is critical to enable implementation of specific control measures and the limitation of virus spread. Further molecular characterization to better understand these viruses is required for the development of diagnostic tests and countermeasures. Advances in molecular biology techniques have revolutionized the procedures for detection and characterization of pathogenic viruses. The development of PCR-based techniques together with DNA sequencing technology, have provided highly sensitive and specific methods to determine virus circulation. Pathogenic viruses potentially having global catastrophic consequences may emerge in regions where capacity for their detection and characterization is limited. Development of a local capacity to rapidly identify new viruses is therefore critical. This article reviews the molecular biology of pathogenic viruses and the basic principles of molecular techniques commonly used for their detection and characterization. The principles of good laboratory practices for handling pathogenic viruses are also discussed. This review aims at providing researchers and laboratory personnel with an overview of the molecular biology of pathogenic viruses and the principles of molecular techniques and good laboratory practices commonly implemented for their detection and characterization.
Emergence of viral diseases
The emergence of infectious diseases has been a threat to public health and global stability. Historically, emerging infectious diseases have caused the deadliest catastrophic pandemics such as the 1918 influenza pandemic (claiming about 50 million lives), the HIV/AIDS pandemic (claiming about 35 million lives so far), etc. (Morens and Fauci, 2013). Emerging infectious diseases are defined as infections whose incidence in humans has increased within the past two decades or threaten to increase in the years to come. The disease emergence can be caused by the spread of a new pathogen, or by the reappearance (or re-emergence) of a known pathogen after a decline in infection (van Doorn, 2014). Biological, social and environmental factors have been linked to the emergence of infectious diseases. These include changes of the pathogens through evolution, changes in the way human populations interact with each other, and with their environment. In addition, increased susceptibility to infection, increased ease of international travel, climate and weather changes, have also been associated with new diseases emergence (van Doorn, 2014). One of the major agents responsible for causing emerging infectious diseases is the virus. Pathogenic viruses that cause emerging diseases are called emerging viruses (Nii-Trebi, 2017).
Cross-species transmission plays an important role in the emergence of viral diseases (Parrish et al., 2008). The majority of the emerging viruses are zoonotic in that, they can be transmitted to humans from animals (Morens and Fauci, 2013). Wildlife, especially mammals and birds, are hosts to a large number of viruses. Most of the mammalian hosts belong to the orders of Chiroptera, Rodentia, Primates and Carnivora. Mammals and birds play an important role as virus reservoirs within which the viruses propagate without causing disease (Mackenzie and Jeggo, 2013). Occasionally these viruses can infect other species including humans. Zoonotic viral infections which cause human diseases may come from domestic animals, poultry, livestock and wildlife. When a virus jumps from animal to human, the phenomenon is called zoonotic spillover which potentially has serious human health and economic impacts (Wang and Crameri, 2014; Plowright et al., 2017). The high risks of viral host switching are highlighted by the emergence of SARS coronavirus (CoV), hantaviruses, Ebola and Marburg viruses, Nipah virus, Hendra virus, and human immunodeficiency virus (HIV) (Parrish et al., 2008).