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Classification of Hemorrhagic Fevers
Published in James H. S. Gear, CRC Handbook of Viral and Rickettsial Hemorrhagic Fevers, 2019
The family Bunyaviridae comprises over 200 viruses (serotypes, subtypes, and varieties) that infect vertebrates and/or invertebrates.3 Four genera of viruses have been defined, namely Bunyavirus, Nairovirus, Phlebovirus, and Ukuvirus. The virions are mostly uniformly spherical, 80 to 110 nm in diameter, and possess a unit membrane envelope from which protrude polypeptide spikes 5 to 10 nm long. They have three helical nucleocapsids, often in the form of supercoiled circles, each consisting of a single species of single-stranded RNA, a major nucleocapsid polypeptide N, and in some cases a large polypeptide which may be a transcriptase component. The genome is composed of three species of RNA, L large, M medium, and S small, organized in end-hydrogen bonded structures. The viruses appear to mature primarily at smooth membrane surfaces and accumulate in Golgi vesicles and saccules. It has been shown that transovarial, venereal, and transstadial transmission in arthropods occurs in some members of the family.
Powassan Virus
Published in Sunit K. Singh, Daniel Růžek, Neuroviral Infections, 2013
Laura D. Kramer, Alan P. Dupuis, Norma P. Tavakoli
In the laboratory, Ix. scapularis has been shown to be a competent vector of POWV. Costero and Grayson reported infection rates of 10%, 40%, and 57% for larvae, nymphs, and females, respectively, after feeding on viremic hosts (Costero and Grayson 1996). Transstadial (larva to nymph, nymph to adult) and transovarial transmission were also reported in this study. Another study demonstrated the transmission of Lineage II/DTV, by infected nymphal Ix. scapularis in as little as 15 minutes after feeding on naive P. leucopus (Ebel and Kramer 2004), suggesting that unlike other tick-borne diseases, such as Lyme, ehrlichiosis, and babesiosis, there is no grace period for removal of an attached tick to prevent POWV infection. The authors of this study also reported transstadial transmission.
Global meta-analysis on Babesia infections in human population: prevalence, distribution and species diversity
Published in Pathogens and Global Health, 2022
Solomon Ngutor Karshima, Magdalene Nguvan Karshima, Musa Isiyaku Ahmed
The overall low global prevalence of 2.23% revealed by the present study may be attributable to factors including low trans-stadial transmission of zoonotic Babesia species which last for 2–3 years, very low parasitemia which can be easily missed by researchers and under-diagnosis in non-or-newly endemic areas [21,91,92]. Although the present study reported low global prevalence of these emerging pathogens, the fatality caused among immunocompromised population calls for concern, especially with the increasing numbers of people living with immunocompromised conditions.