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Amebic Meningoencephalitis (PAM) is caused by an ameba called Naegleria
information on all types of amebic central nervous system infections including
PAM, see http://www.dshs.texas.gov/IDCU/disease/Amebic-Central-Nervous-System-(CNS)-Infections.doc.
meningitis/encephalitis infections are not spread from person to person.
Naegleria fowleri infects people when water containing the ameba enters the
body through the nose. This typically occurs when people go swimming or diving
in warm freshwater places, like lakes and rivers. In very rare instances, Naegleria
infections may also occur when contaminated water from other sources (such as
inadequately chlorinated swimming pool water or contaminated tap water) enters
the nose, such as when people submerge their heads or cleanse their noses
during religious practices, and when people irrigate their sinuses (nose) using
contaminated tap water. The Naegleria fowleri ameba then travels up the
nose to the brain where it destroys the brain tissue. Naegleria fowleri
has not been shown to spread via water vapor or aerosol droplets (such as
shower mist or vapor from a humidifier), and you cannot be infected with Naegleria
fowleri by drinking contaminated water.
infections with Naegleria fowleri are rare, they occur mainly during the
summer months of July, August, and September. Infections are more likely to
occur in southern-tier states. Infections usually occur when it is hot for
prolonged periods of time, which results in higher water temperatures and lower
In its early stages, symptoms of PAM
may be similar to symptoms of bacterial meningitis. Initial symptoms of PAM
start about 5 days (range 1 to 9 days) after infection. The initial symptoms
may include headache, fever, nausea, or vomiting. Later symptoms can include
stiff neck, confusion, lack of attention to people and surroundings, loss of balance,
seizures, and hallucinations. After the start of symptoms, the disease
progresses rapidly and usually causes death within about 5 days (range: 1 to 18
PAM disproportionately affects males
and children. The reason for this distribution pattern is unclear but may
reflect the types of water activities (such as diving or watersports) that
might be more common among young boys. The extremely low occurrence of PAM
makes epidemiologic study difficult.
infections are severe, the risk of Naegleria fowleri infection is very
low. There have been 30 reported infections in the U.S. during the 10 years
from 2000-2009, despite millions of recreational water exposures each year. By
comparison, during the ten years from 1996 to 2005, there were over 36,000
drowning deaths in the U.S. It is likely that a low risk of Naegleria
fowleri infection will always exist with recreational use of warm
freshwater lakes, rivers, and hot springs. The low number of infections makes
it difficult to know why some people have been infected compared to the
millions of other people using the same or similar waters across the U.S. The
only way to prevent Naegleria fowleri infection is to refrain from
water-related activities. If you do plan to take part in water-related
activities, here are some measures that might reduce risk:
- Avoid water-related activities in
bodies of warm freshwater during periods of high water temperature and low
- Hold the nose shut or use nose clips
when taking part in water-related activities in bodies of warm freshwater such
as lakes, rivers, or hot springs.
- Avoid putting your head under the
water in hot springs and other untreated thermal waters.
- Avoid digging in or stirring up the
sediment while taking part in water-related activities in shallow, warm,
- Use only sterile, distilled, or
lukewarm previously boiled water for nasal irrigation or sinus flushes (e.g.,
Neti Pot usage, ritual nasal ablution, etc.).
Recent Texas Trends
Primary Amebic Meningoencephalitis (PAM)/Naegleria fowleri:
From 1972-2015, there have been a total of 34 cases of PAM
reported to the Texas Department of State Health Services (DSHS). The median age of PAM cases reported during this
period was 9.5 years (range: 3 years to 37 years); 76% of cases-patients were
male. Cases have occurred from July through November, with most cases occurring
in August. Most case-patients reported recent exposure to freshwater lakes,
ponds, and rivers during the warm summer months. No Texas cases have been
linked to nasal irrigation or sinus flushes.