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Rabies is caused by a rod- or bullet-shaped virus
in the family Rhabdoviridae. The virus is usually transmitted via an
animal bite, however, cases have also been reported in which the
virus penetrated the body through infected saliva, moist tissues
such as the eyes or lips, a scratch on the skin, or the
transplantation of infected tissues. Inhalation of the virus in the
air, as might occur in a highly populated bat cave, is also thought
to occur.
From the bite or other area of penetration, the
virus multiplies as it spreads along nerves that travel away from
the spinal cord and brain (efferent nerves) and into the salivary
glands. The rabies virus may lie dormant in the body for several
weeks or months, but rarely much longer, before symptoms appear.
Initially, the area around the bite may burn and be painful. Early
symptoms may also include a sore throat, low-grade fever, headache,
loss of appetite, nausea and vomiting, and diarrhea. Painful spasms
develop in the muscles that control breathing and swallowing. The
individual may begin to drool thick saliva and may have dilated or
irregular pupils, increased tears and perspiration, and low blood
pressure.
Later, as the disease progresses, the patient
becomes agitated and combative and may exhibit increased mental
confusion. The affected person usually becomes sensitive to touch,
loud noises, and bright lights. The victim also becomes extremely
thirsty, but is unable to drink because swallowing is painful. Some
patients begin to dread water because of the painful spasms that
occur. Other severe symptoms during the later stage of the disease
include excessive salivation, dehydration, and loss of muscle tone.
Death usually occurs three to 20 days after symptoms have developed.
Unfortunately, recovery is very rare. |
