Skip to Main Content

We have a new app!

Take the Access library with you wherever you go—easy access to books, videos, images, podcasts, personalized features, and more.

Download the Access App here: iOS and Android


These viruses are presented in alphabetical order. They are listed in Table 46–1 in terms of their nucleic acid and presence of an envelope.

Table 46–1Minor Viral Pathogens


Astrovirus is a nonenveloped RNA virus similar in size to poliovirus. It has a characteristic five- or six-pointed star appearance in the electron microscope. It causes watery diarrhea, especially in children. Most adults have antibodies against astrovirus, suggesting that infection occurs commonly. No antiviral drugs or preventive measures are available.


BK virus is a member of the polyomavirus family. Polyomaviruses are nonenveloped viruses with a circular, double-stranded DNA genome. BK virus and JC virus (see Chapter 44) are the two polyomaviruses that infect humans.

BK virus infection is widespread as determined by the presence of antibody and is typically acquired in childhood, and infection is not associated with any disease at that time. It does, however, cause nephropathy and graft loss in immunosuppressed renal transplant patients. Asymptomatic shedding of BK virus in the urine of immunocompromised patients and pregnant women in the third trimester occurs. There is no antiviral therapy effective against BK virus.


Borna virus is an enveloped virus with a nonsegmented, single-strand, negative-polarity RNA genome. It has the smallest genome of any virus with this type of RNA and is the only virus of this type to replicate in the nucleus of the infected cell. DNA sequences homologous to the Borna virus genome are integrated into human cellular DNA. It is a neurotropic virus known to infect regions of the brain such as the hippocampus.

Borna is the name of a town in Germany where the virus caused a disease in horses in 1885. It is primarily a zoonotic virus causing disease in domestic animals, such as cattle, sheep, dogs, and cats. In humans, Borna virus often causes fatal encephalitis. In addition, there is evidence that it is associated with human psychiatric diseases characterized by abnormal behavior, such as bipolar disorder.


This virus was first isolated in Utah in 1956 but is found throughout the Western Hemisphere. It is a bunyavirus transmitted by Aedes, Anopheles, or Culiseta mosquitoes ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.