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LA Times Health - The Unreal World - The Invasion
LA Times Health - The Unreal World - The Invasion
The Unreal World
Dr. Marc Siegel
August 27, 2007
Truth about behavioral changes
"The Invasion," Warner Bros., premiered Aug. 17
The premise: In this fourth attempt at putting Jack Finney's classic "The
Body Snatchers" to the screen, there is a new twist. This time, instead of
plant-like pods, it's an alien virus-like particle attached to the wreckage
of the NASA Shuttle Patriot, and it begins to spread rapidly through the
human population. The virus (in the jargon of the movie) interferes with
sweat, causes a "cellular condensation," a "metabolic reaction" and alters
the body's "genetic expression" by the "integration of alien DNA" -- while
turning everyone into emotionless robots.
The medical questions: Gobbledygook aside, are there real-life examples of
infections that infect brain tissue and alter behavior and emotion, or is
this all science fiction?
The reality: In animals, there are plenty of examples of viruses and
parasites that change a creature's behavior, sometimes in a way that appears
to benefit the invader. The rabies virus, for example, causes increased
saliva flow and aggression. Both, it's been pointed out, benefit the virus
since it is transmitted in spittle through bites. Rodents infected with a
parasite called Toxoplasma gondii lose their fear of the scent of cats,
which is useful for the parasite since it replicates in the guts of cats.
In humans beings, small infectious protein particles known as prions are
responsible for an array of rare, related, degenerative brain disorders that
cause changes in behavior as early symptoms. Prions mostly affect the
brain's gray matter, causing loss of nerve function and spongy holes to form
in the brain. In Creutzfeldt-Jakob disease, one of these rare prion
disorders, patients suffer progressive dementia, volatile emotions,
difficulty walking and muscular jerks. (Kuru was another historical example
of CJD in Papua, New Guinea, in the early 20th century: The disorder spread
because of the tribal practice of eating brains at funerals.) Bovine
spongiform encephalopathy, also known famously as mad cow disease, is a
similar disorder that has been epidemic in cattle but has rarely affected
humans because of a species barrier.
Fatal familial insomnia is a human prion disease characterized by wild
shifts in the body's vital signs as well as by loss of sleep.
Viral encephalitis (inflammation of the brain -- mostly the gray matter) is
commonly caused by arboviruses including West Nile, herpes viruses and
enteroviruses. Common symptoms include irritability, lethargy and seizures.
And rabies, a deadly form of encephalitis, causes irritation and agitation
and later, hallucinations. Luckily, rabies is rare in the U.S., with one or
two human cases reported each year.
Borna disease virus was first described in horses in 1766, but since has
been associated with a variety of animals, including humans. In animals, it
has been known to cause hyperactivity, somnolence, depression and agitation.
Although a causal link hasn't been established, traces of the virus in man
have been found in significant numbers of depressed and schizophrenic
patients. Borna appears to spread in animals by direct contact through
saliva and nasal secretions. Once in the body, it spreads from peripheral
nerves back toward the central nervous system.
Subacute sclerosing panencephalitis is caused by direct invasion of the
brain by mutant measles viruses. There are fewer than 10 cases a year in the
U.S. The disease tends to occur years after the patient appears to have
recovered from measles. Symptoms include gradual behavioral change leading
to bizarre behavior, muscle jerks, unsteady walking, seizures and frequently
death within one to two years.
Dr. Marc Siegel is an internist and an associate professor of medicine at
New York University's School of Medicine. In the Unreal World, he explains
the medical facts behind the media fiction. He can be reached at
marc@doctorsiegel.com. |
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