outbreak of unexplained illness occurred
in May 1993 in the "Four
Corners," an area of the Southwest US shared
by New Mexico, Arizona, Colorado, and Utah.
A number of previously healthy young adults
suddenly developed acute respiratory symptoms;
about half soon died. The New Mexico Department
of Health, the Arizona Department of Health
Services, the Colorado Department of Health,
the Utah Department of Health, the Indian Health
Service and CDC, with the assistance of the
Navajo Nation Division of Health, rapidly mounted
an intensive investigation. Researchers soon
suspected that they were dealing with a form
of hantavirus, which is transmitted by rodents.
Researchers then investigated the possible
rodent connection, trapping rodents in the
affected area, doing tissue studies both of
rodents and hantavirus victims, until the virus
and its principal carrier—the deer mouse—were
positively identified. Why the Four Corners
area? Simply because there was a "bumper
crop" of rodents there, due to heavy rains
during the spring of 1993, which produced an
extra-plentiful supply of the foods that rodents
eat. Early on, it was also established that
person-to-person spread was unlikely. It was
also determined that this "new" hantavirus
had actually been present, but unrecognized,
at least as early as 1959. Since the 1993 outbreak,
hantavirus pulmonary syndrome (HPS) has been
identified in over half of the states of the
Transmission: When exposed to
rodents (deer mouse, white-footed mouse, cotton
rat and rice rat) Transmission occurs via rodent
saliva/dry droppings. The virus is "aerosolized" and
breathed in. (This is how the virus is transmitted.) Transmission does not occur from other
people, other animals or insects. Dogs may bring
rodents into the house which are effected, but
dogs, chickens, hamsters, sheep, goats and llamas
and alpacas (and many other animals) may get
the virus but are not carriers. That is, they
cannot spread the virus and infect other animals.
You can also become infected by touching the
mouth or nose after handling contaminated materials.
A rodent's bite can also spread the virus.
The deer mouse (Peromyscus
maniculatus) is a deceptively cute animal, with
big eyes and big ears. Its head and body are
normally about 2 - 3 inches long, and the tail
adds another 2 - 3 inches in length. You may
see it in a variety of colors, from gray to reddish
brown, depending on its age. The underbelly is
always white and the tail has sharply defined
white sides. The deer mouse is found almost everywhere
in North America. Usually, the deer mouse likes
woodlands, but also turns up in desert areas.
The cotton rat (Sigmodon hispidus), which you'll
find in the southeastern United States (and way
down into Central and South America), has a bigger
body than the deer mouse—head and body
about 5 - 7 inches, and another 3 - 4 inches
for the tail. The hair is longer and coarser,
of a grayish brown color, even grayish black.
The cotton rat prefers overgrown areas with shrubs
and tall grasses.
The rice rat (Oryzomys palustris) is slightly
smaller than the cotton rat, having a head and
body 5 - 6 inches long, plus a very long, 4-
to 7-inch tail. Rice rats sport short, soft,
grayish brown fur on top, and gray or tawny underbellies.
Their feet are whitish. As you might expect from
the name, this rat likes marshy areas and is
semi-aquatic. It's found in the Southeastern
United States and into Central America.
The white-footed mouse (Peromyscus leucopus)
is hard to distinguish from the deer mouse. The
head and body together are about four inches
long. You should note that its tail is normally
shorter than its body (about 2 - 4 inches long).
Topside, its fur ranges from pale brown to reddish
brown, while its underside and feet are white.
The white-footed mouse is found through southern
New England, the Mid-Atlantic and Southern states,
the Midwest and into the western states and Mexico.
It prefers wooded and brushy areas, although
sometimes it will live in more open ground.
Sometimes, the "country mouse" becomes
a "city mouse". Both the deer mouse
and the cotton rat are usually in rural areas,
but can also be found in cities when conditions
are right, such as easy availability of food,
water and shelter.
Other rodents may also carry hantavirus. It appears
that other rodents carrying strains of hantavirus
that cause HPS are yet to be identified. In addition,
yet other rodent species play host to other types
of hantaviruses that cause a different type of
infection, hemorrhagic fever with renal syndrome,
or HFRS. See " hantavirus" for more
information. It is wise, therefore, to avoid
close contact with rodents in general.
Killing the virus: Hantavirus is not spread from
person to person. Being near a person who has
hantavirus pulmonary syndrome cannot infect you.
The virus, which is able to survive in the environment
(for example, in contaminated dirt and dust),
can be killed by most household disinfectants,
such as bleach or alcohol. The virus is most
active when the temperature is between 45 and
72 degrees Fahrenheit.
Symptoms Symptoms of hantavirus pulmonary syndrome
usually appear within 2 weeks of infection but
can appear as early as 3 days to as late as 6
weeks after infection. The primary symptom of
this disease is difficulty in breathing, which
is caused by fluid build-up in the lungs and
quickly progresses to an inability to breathe.
First symptoms are general and flu-like: fever
(101-104 F); headache; abdominal, joint, and
lower back pain; sometimes nausea and vomiting.
However, the primary symptom of this disease
is difficulty in breathing, which is caused by
fluid build-up in the lungs and quickly progresses
to an inability to breathe.
If any combination of the symptoms described
above especially difficulty in Breathing appear
after direct or indirect exposure to rodents,
contact your doctor or public health clinic immediately
and be sure to mention your exposure to rodents.
At the present time, there is no specific treatment
for the hantavirus infection. However, we do
know that if the infected individuals are recognized
early and are taken to an intensive care unit,
some patients may do better. In intensive care,
patients are intubated and given oxygen therapy
to help them through the period of severe respiratory
distress. The earlier the patient is brought
in to intensive care, the better. If a patient
is experiencing full distress, it is less likely
the treatment will be effective. Therefore if
you have been around rodents and have symptoms
of fever, deep muscle aches and severe shortness
of breath, see your doctor immediately. Be sure
to tell your doctor that you have been around
rodents—this will alert your physician
to look closely for any rodent-carried disease
such as HPS.
To minimize the risk for hantavirus infection,
follow these precautions:
- Before occupying abandoned or unused cabins,
open them up to air out.
- Inspect for rodents
and do not use cabins if you find signs of
rodent infestation. If you sleep outdoors,
check potential campsites for rodent droppings
- Do not disturb rodents, burrows,
- Avoid sleeping near woodpiles or
garbage areas that may be frequented by Rodents.
- Avoid sleeping on bare ground; use a mat
or elevated cot if they are available.
foods in rodent-proof containers and promptly
discard, bury, or burn all garbage.