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Psittacosis (Due to Chlamydia psittaci)

Reviewed for currency January 14, 2021 Psittacosis is a systemic infection that frequently causes pneumonia. Its relationship to bird exposure has been known for more than 100 years. In 1879, Ritter studied an outbreak in Switzerland and called it pneumotyphus. Morange applied the term psittacosis (from the Greek word for parrot) in 1892 after studying cases associated with sick parrots. In 1930, the organism was identified…

Chlamydia trachomatis (Trachoma and Urogenital Infections)

Revised August 2, 2021 Chlamydia trachomatis imposes a tremendous burden on human health because it is one of the most common causes of bacterial infection. Worldwide in 2011, an estimated 21 million people had active trachoma, which is an ocular C. trachomatis infection that is the leading cause of infectious blindness. The World Health Organization (WHO) estimated that in 2016, 1.9 million individuals were blind or…

Prions and Prion Disease of the Central Nervous System (Transmissible Neurodegenerative Diseases)

Reviewed for currency February, 2020 Prions are the transmissible agents of a class of neurodegenerative diseases of humans and other mammals. Prions differ from other infectious agents in that they contain no information-bearing nucleic acid. Rather, they are composed mainly, perhaps only, of abnormal conformations of a normally produced cell surface glycoprotein called the prion protein (PrP). These abnormal conformations of PrP are able to trigger…

Hepatitis E Virus

Revised March 29, 2022 Hepatitis E virus (HEV) is a ribonucleic acid (RNA) virus that causes a viral hepatitis that is indistinguishable from other forms of viral hepatitis. The World Health Organization (WHO) estimates a global incidence of 20 million cases of HEV infection annually, accounting for 3.3% of mortality from viral hepatitis. HEV infection most often results in an acute, self-limited disease that does not…

Astroviruses and Picobirnaviruses

Reviewed for currency February, 2020 Viral gastroenteritis is caused largely by noroviruses and sapoviruses (see Chapter 176 ) and by rotaviruses (see Chapter 150 ). Astroviruses are also established as important causes of gastroenteritis, albeit substantially less frequently than the aforementioned viruses. Picobirnaviruses are more recently described viruses that have a possible, although not yet established, role as agents of gastroenteritis. Astroviruses Virology Classification Astroviruses are…

Noroviruses and Sapoviruses (Caliciviruses)

Reviewed for currency November, 2019 Revised February 20, 2021 Acute infectious gastroenteritis is an exceedingly common and widespread illness throughout the world. Noroviruses are major causes of this illness, which is generally self-limited but can result in hospitalization, mortality in young children in the developing world, and severe illness in elderly and immunocompromised patients. Sapovirus, another calicivirus, and Astrovirus (see Chapter 177 ) also cause gastroenteritis…

Rhinovirus

Rhinoviruses are among the most frequent causes of viral infections in humans. They are the major cause of the common cold and are significant contributors to other upper respiratory syndromes as well as certain lower respiratory illnesses. The term common cold is believed to derive from ancient descriptions of illness in traditional Chinese and Roman sources, in which the illness was believed to be caused by…

Hepatitis A Virus

Hepatitis A is generally an acute, self-limited infection of the liver by an enterically transmitted picornavirus, hepatitis A virus (HAV). Infection may be asymptomatic or result in acute hepatitis. Rarely, fulminant hepatitis can ensue. Although the duration and severity of symptoms vary widely, HAV infections never cause chronic liver disease. The availability of effective vaccines against hepatitis A has markedly affected the epidemiology of hepatitis A…

Parechoviruses

Historical Background The initial two serotypes of the genus Parechovirus were isolated in 1956 from children with diarrhea. On the basis of the scheme used at that time for the classification of the enteroviruses, they were classified as echovirus (E) serotypes 22 (Harris strain) and 23 (Williamson strain). After their classification as enteroviruses, it became evident that they differed from other serotypes within the genus. Their…

Coxsackieviruses, Echoviruses, and Numbered Enteroviruses (EV-A71, EVD-68, EVD-70)

This chapter covers human disease caused by the group A coxsackieviruses (CVs), group B CVs, echoviruses (Es), and the numbered enteroviruses (EVs), which are distributed among four species, EV-A to EV-D, of the genus Enterovirus. Viral diseases caused by the closely related and newly designated genus Parechovirus , of the Picornaviridae, are discussed in Chapter 173 . These viruses have many physical, epidemiologic, and pathogenetic characteristics…

Poliovirus

Revised February 13, 2021 Polioviruses are the cause of poliomyelitis, a systemic viral infection that predominantly affects the central nervous system (CNS), causing paralysis. The name of the disease ( polios, “gray”; myelos, “marrow” or “spinal cord”), now commonly shortened to polio, is descriptive of the pathologic lesions that involve neurons in the gray matter, especially in the anterior horns of the spinal cord. Paralytic poliomyelitis…

Introduction to the Human Enteroviruses and Parechoviruses

Members of the genera Enterovirus and Parechovirus are picornaviruses. Picornaviridae is a large family of morphologically identical, single-stranded, positive-sense RNA viruses that share similar genomic and structural organizations. Originally the human enteroviruses were divided into five species on the basis of differences in host range and pathogenic potential: polioviruses, group A coxsackieviruses (CV-A), group B coxsackieviruses (CV-B), echoviruses (E), and newer enteroviruses (EVs) ( Table 170.1…

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A 48-Year-Old Woman from Thailand With Fever and Disseminated Cutaneous Abscesses

Clinical Presentation History A 46-year-old Thai woman is transferred to a German clinic for tropical diseases with a 2-month history of recurrent cutaneous and subcutaneous abscesses, progressive lymphadenopathy and weight loss. Despite various antibiotic therapies, clinical symptoms and inflammatory markers had deteriorated, resulting in hospital admission. Pus and blood cultures did not yield any growth, and histopathology of a lymph node biopsy showed non-specific lymphadenitis. The…

A 6-Year-Old Boy from Malawi With Proptosis of the Left Eye

Clinical Presentation History A 6-year-old Malawian boy from the lakeshore of Lake Malawi presents with a painless, proptosed left eye that his family first noticed 3 weeks ago. It has worsened rapidly though his vision is still normal. He denies any pain. Clinical Findings On examination he is afebrile, the right eye is normal, the left eye is proptosed but non-pulsating ( Fig. 60.1 ). The…

Conclusions

Introduction We live in an age of constant change, due, to a large degree, to the continuing threat of infection by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causative agent of COVID-19. This recently emerged pandemic coronavirus has spread throughout the world. Countries or parts of countries have responded by locking down segments of their areas, in some cases, literally preventing the population from leaving their…

Omsk Hemorrhagic Fever Virus

Introduction Omsk hemorrhagic fever is an acute disease caused by the Omsk hemorrhagic fever virus (OHFV) and is prevalent in some areas of western Siberia. OHFV is one of the tickborne flaviviruses that is known to cause hemorrhagic fever, in league with Kyasanur forest disease virus (KFDV) in southern India and the Alkhurma hemorrhagic fever virus (AHFV) variant subset of KFDV in Saudi Arabia, as well…

Kyasanur Forest Disease and Alkhurma Hemorrhagic Fever Viruses

Introduction Alkhurma hemorrhagic fever virus (AHFV) is present in Saudi Arabia and surrounding regions. It has 89%–92% homology with Kyasanur Forest disease virus (KFDV), found primarily in India. Genome sequencing has revealed that AHFV and KFDV are very similar in polyprotein properties, C and E proteins, RNA–RNA interaction sequences, NS3 and NS5 polymerase, as well as 5′ untranslated region structures. AHFV is now classified as a…