Invasive Group A Strep
What is group A streptococcus (GAS)?
Group A streptococci are bacteria commonly found in the throat and
on the skin. The vast majority of GAS infections are relatively mild illnesses,
such as strep throat and impetigo. Occasionally, however, these bacteria
can cause much more severe and even life-threatening diseases such as
necrotizing fasciitis (occasionally described by the media as łthe flesh-eating
bacteria˛) and streptococcal toxic shock syndrome (STSS). In addition,
people may carry group A streptococci in the throat or on the skin and
have no symptoms of disease.
How are group A streptococci spread?
These bacteria are spread by direct contact with nose and throat
discharges of an infected individual or with infected skin lesions. The
risk of spread is greatest when an individual is ill, such as when people
have strep throat or an infected wound. Individuals who carry the bacteria
but have no symptoms are much less contagious. Treatment of an infected
person with an appropriate antibiotic for 24 hours or longer eliminates
contagiousness. However, it is important to complete the entire course
of antibiotics as prescribed. Household items like plates, cups, toys,
etc., do not play a major role in disease transmission.
What is invasive group A streptococcal disease?
Invasive GAS disease is a severe and sometimes life-threatening infection
in which the bacteria have invaded parts of the body, such as the blood,
deep muscle and fat tissue, or the lungs. Two of the most severe, but
least common, forms of invasive GAS disease are called 'necrotizing fasciitis'
(infection of muscle and fat tissue) and 'streptococcal toxic shock syndrome'
(a rapidly progressing infection causing low blood pressure/shock and
injury to organs such as the kidneys, liver and lungs). Approximately
20 percent of patients with necrotizing fasciitis and 60 percent with
STSS die. Only about 10-15 percent of patients with other forms of invasive
group A streptococcal disease die.
How common is invasive group A Streptococcal disease?
Approximately 10,000-15,000 cases of invasive GAS disease occur in
the United States each year resulting in more than 2,000 deaths. The Centers
for Disease Control and Prevention estimates there are between 500-1,500
cases of necrotizing fasciitis and 2,000-3,000 cases of STSS each year
in the United States. In contrast, there are several million cases of
strep throat and impetigo annually. Clusters of cases or outbreaks of
invasive GAS have not been reported in any schools or communities in New
York State.
Why does invasive group A streptococcal disease occur?
Invasive group A streptococcal infections occur when the bacteria
gets past the defenses of the person who is infected. This may occur when
a person has sores or other breaks in the skin that allow the bacteria
to get into the tissue. Health conditions that decrease a person's immunity
to infection also make invasive disease more likely. In addition, there
are certain strains of GAS that are more likely to cause severe disease
than others. The reason why some strains will cause more severe illness
is not totally clear but may involve the production of substances (toxins)
that cause shock and organ damage, and enzymes that cause tissue destruction.
Who is most at risk of invasive group A streptococcal disease?
Few people who come in contact with a virulent strain of GAS will
develop invasive GAS disease; most will have a routine throat or skin
infection and some may have no symptoms whatsoever. Although healthy people
can get invasive GAS disease, people with chronic illnesses like cancer,
diabetes and kidney dialysis, and those who use medications such as steroids,
are at higher risk. In addition, breaks in the skin, like cuts, surgical
wounds or chickenpox may provide an opportunity for the bacteria to enter
the body.
Can invasive group A streptococcal disease be treated?
Group A streptococcus bacteria can be treated with common, inexpensive
antibiotics. Penicillin is the drug of choice for both mild and severe
disease. For penicillin-allergic patients with mild illness, erythromycin
can be used, although occasional resistance has been seen. Clindamycin
may be used to treat penicillin allergic patients with more severe illness
and can be added to the treatment in cases of necrotizing fasciitis or
STSS. Certain other antibiotics also are effective. In addition to antibiotics,
supportive care in an intensive care unit and sometimes surgery are necessary
with these diseases. Early treatment may reduce the risk of death although,
unfortunately, even appropriate therapy does not prevent death in every
case.
Should contacts of individuals with invasive group A streptococcal disease
be tested and treated?
There have been no reports of casual contacts, like co-workers or
school classmates, developing invasive GAS disease following contact with
a person who developed invasive GAS disease. However, on occasion, close
contacts such as family members have developed severe disease. Because
studies are limited, there are no current recommendations indicating very
close contacts (e.g., household members or those having direct contact
with secretions) of individuals with necrotizing fasciitis or STSS should
be tested for infection. Some feel that cultures of the throat and of
any skin lesions should be obtained. If cultures are positive, treatment
should be given using an antibiotic that is highly effective in eliminating
GAS from the throat. If contacts have symptoms suspicious for GAS disease
or would be at higher risk of invasive disease if infected (diabetes,
cancer, chronic heart disease, alcoholism, etc.), therapy may be started
while waiting for culture results.
What can be done to help prevent invasive group A streptococcal infections?
The spread of all types of group A streptococcal infections may be
reduced by good handwashing, especially after coughing and sneezing, and
before preparing foods and before eating. Persons with sore throats should
be seen by a physician who can perform tests to find out whether it is
strep throat; if so, one should stay home from work, school or daycare
until after 24 hours or more after taking an antibiotic. All wounds should
be kept clean. Wounds should be watched for possible signs of infection
which include increasing redness, swelling and pain at the wound site.
If these signs occur, especially in a person who also has a fever, consult
a doctor immediately.
What are the early signs and symptoms of necrotizing fasciitis and streptococcal
toxic shock syndrome?
Early signs and symptoms of necrotizing fasciitis include fever,
severe pain and swelling, and redness at the wound site. Early signs and
symptoms of STSS may include fever, dizziness, confusion, rash and abdominal
pain.
Revised: 3/96
Source: NY State Department of Health
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