WORLD OF MICROBIOLOGY AND IMMUNOLOGY Herpes and herpes virus267•
include rapid mutation of the virus. Treatment with interferon
remains the most effective measure in managing the long term
effects of HCV.
Undiscovered until 1980, Hepatitis E virus (HEV) is
thought to transmit in a similar fashion to HAV. HEV is most
prevalent in India, Asia, Africa, and Central America.
Contaminated water supplies, conditions that predispose to
poor hygiene (as in developing countries), and travel to devel-
oping countries all contribute to the spread of HEV. Symptoms
are similar to other hepatitis viruses and, like HAV, it is usu-
ally self-limiting, does not develop into the chronic stage, and
seldom causes fatal liver damage. It does seem, however, that
a higher percentage of pregnant women (from 10–20%) die
from HEV than from HAV.
Research into the virus was slow because of the limited
amounts which could be isolated and collected from both nat-
urally infected humans and experimentally infected primates.
Recently, successful genetic cloning(artificial duplication of
genes) is greatly enhancing research efforts. Surprisingly,
research found that antibodies exist in between one to five per-
cent of people who have never been infected with hepatitis.
Until an effective vaccine is developed, sanitation remains the
most important factor in preventing the spread of HEV.
Because it is a “defective” virus requiring “coinfection”
with HBV in order to live and reproduce, HDV alone poses no
threat in the spread of viral hepatitis. It also poses no threat to
people vaccinated against HBV. However, when this
extremely infectious and potent virus is contracted by unsus-
pecting carriers of HBV, rapidly developing chronic and even
fatal hepatitis often follows. The coexistent requirements of
HDV as yet remain unclear. Research into development of an
effective vaccine is ongoing, and genetic cloning may aid in
this effort.
Little is currently known about a relatively recently dis-
covered hepatitis virus, G. HGV appears to be passed through
contaminated blood, as is HCV. In fact, many infections with
HVG occur in people already infected with HCV. HGV, how-
ever, does not seem to change the disease course in people
infected with both HCV and HGV. In cases of isolated HGV
infection, little liver injury is noted, and there does not appear to
be a risk of chronic liver injury. Much more information must
be sought about this particular hepatitis virus, and its risks.See alsoEpidemics, viral; Interferon actions; Public health,
current issues; Viruses and responses to viral infectionHEPATITIS, AUTOIMMUNE•seeAUTOIMMUNITY
AND AUTOIMMUNE DISORDERSHHerpes and herpes virusERPES AND HERPES VIRUS
Herpes is a name given to a common viral infection. The
infection can occur in the mouth and in the genitals.
The two forms of herpes are caused by two forms of a
herpes virus. Both forms are called herpes simplex virus. Oralherpes is generally caused by herpes simplex type 1 (that is
typically shortened to HSV–1). It is also known as human her-
pes virus 1 (HHV1). Genital herpes is generally caused by her-
pes simplex type 2 (shortened to HSV–2, which has also been
called human herpes virus 2, or HHV2). However, HSV–1 can
cause genital herpes and HSV–2 can cause oral herpes.
There are eight herpes virus types known in humans.
HSV–1 (HHV1) and HSV-2 (HHV2) are the forms associated
with oral and genital herpes. Human herpes virus 3 is also
known as varicella zoster virus, and is the cause of chicken-
pox. HHV4 is the official name of Epstein-Barr virus, the
major cause of infectious mononucleosis. HHV5 is also
known as cytomegalovirus. It can cause mononucleosis, hep-
atitisin newborns, and complications in AIDSpatients. HHV6
causes roseola in children and fever-associated seizures in
infants. HHV7 has not yet been associated with any disease,
and appears to be present in almost all people. Infection with
HHV7 likely occurs early in life. Finally, HHV8 contributes to
Kaposi’s sarcoma, a relatively rare cancer that predominantly
afflicts AIDS patients whose immune systems are failing.Rash due to Herpes zoster virus.womi_H 5/6/03 3:20 PM Page 267