What is PAM, Incubation period, Early symptoms, Diagnosis

PAM (Primary Amoebic Meningoencephalitis) is a rare but deadly disease caused by the Naegleria fowleri amoeba.

Pathogen: Naegleria fowleri is a single-celled amoeba that lives in warm freshwater, such as lakes, rivers, and hot springs.

Naegleria fowleri, commonly known as the brain-eating amoeba, is a free-living amoeba found in warm freshwater environments. While it prefers warm water habitats, it can survive for short periods in other conditions. Here’s how long it can survive in various environments:

  1. Moist Surfaces: Naegleria fowleri can survive for a limited time on moist surfaces, such as damp soil, wet towels, or moist fabrics. In these conditions, it may survive for a few hours to a couple of days, depending on factors like temperature and humidity.
  2. Dry Surfaces: On dry surfaces, such as dust or dry fabrics, Naegleria fowleri is less likely to survive for extended periods. It typically cannot survive for more than a few hours to a day in dry conditions.
  3. Household Environment: In a typical household environment, where surfaces may vary from dry to moist, the survival time of Naegleria fowleri would depend on factors like humidity levels, temperature, and the presence of organic matter. Generally, it may survive for several hours to a couple of days on surfaces like bathroom tiles, wet towels, or damp clothing.
  4. Bed Covers: On bed covers or bedding materials, Naegleria fowleri may survive for a similar duration as on other moist surfaces, typically ranging from a few hours to a couple of days.
  5. Survival on Skin: Naegleria fowleri does not typically survive on intact skin. The outer layer of the skin acts as a protective barrier against microorganisms. However, if water contaminated with Naegleria fowleri enters the nose and reaches the olfactory nerve, it can potentially cause infection.
  6. Survival Outside of Water: Naegleria fowleri is primarily a waterborne organism and requires a warm and moist environment to survive and proliferate. Once outside of water or a suitable environment, such as soil or dust, the amoeba’s survival is limited. It is not well adapted to survive for extended periods outside of water.
  7. Transmission from Dust: There is no evidence to suggest that Naegleria fowleri can be transmitted directly from dust. The primary route of infection is through the inhalation of contaminated water droplets into the nasal passages, where the amoeba can travel to the brain.

It’s essential to note that while Naegleria fowleri can survive for some time outside of its preferred aquatic habitats, the risk of infection primarily comes from water-related activities where the amoeba can enter the body through the nose, such as swimming in warm freshwater lakes, rivers, or poorly maintained swimming pools.

Taking precautions such as avoiding nasal contact with contaminated water and properly maintaining swimming areas can help reduce the risk of infection

Transmission: The amoeba enters the body through the nose when contaminated water is forcefully pushed up the nasal passages, such as during swimming or diving.

While it can be found in various regions worldwide, certain areas are known to have larger natural freshwater reservoirs where the amoeba may thrive. Here’s a general ranking of regions with significant freshwater reservoirs where Naegleria fowleri may be present:

  1. Southern United States: Warm climates and abundant freshwater sources, such as lakes, rivers, and hot springs, make the southern United States, particularly states like Texas, Florida, and Louisiana, significant habitats for Naegleria fowleri.
  2. Southeast Asia: Regions with tropical climates, including Southeast Asia, may have suitable conditions for the survival of Naegleria fowleri in freshwater bodies, although specific reservoirs may vary.
  3. Australia: Certain freshwater reservoirs in Australia, particularly those with warm temperatures and stagnant or slow-moving water, may harbor Naegleria fowleri.
  4. Africa: Several regions in Africa, including countries with warm climates and abundant freshwater sources, may have environments conducive to the survival of Naegleria fowleri.

Regions with significant cold-freshwater reservoirs:

  • Siberian Water Reservoirs: While Siberia may have freshwater reservoirs, the cold climate in many parts of Siberia is not typically conducive to the survival of Naegleria fowleri.
  • Alaska Reservoirs: Similar to Siberia, the cold climate in Alaska may limit the presence of Naegleria fowleri in freshwater reservoirs.
  • Canadian Reservoirs: Canada has various freshwater reservoirs, but the prevalence of Naegleria fowleri in Canadian waters may be lower compared to warmer regions.

Regarding the presence of Naegleria fowleri in China and its borders with neighboring countries:

  • China: While there may be freshwater bodies in China where Naegleria fowleri could potentially survive, information on its prevalence in Chinese waters may be limited.
  • Borders with Russia, Mongolia, and North Korea: There is limited information on the presence of Naegleria fowleri specifically along these borders. Factors such as climate, water temperature, and water quality would influence the suitability of freshwater reservoirs for the amoeba’s survival.

While Naegleria fowleri can be found in various freshwater environments worldwide, its presence and prevalence may vary depending on local environmental conditions. Routine monitoring of water quality and public health advisories are essential for managing the risk of infection

Incubation period: The incubation period is typically between 1-9 days, with an average of 5 days.

Early symptoms: The early symptoms of PAM include fever, headache, nausea, vomiting, and a stiff neck.

Diagnosis: PAM is diagnosed through a combination of clinical symptoms, laboratory testing of cerebrospinal fluid (CSF), and imaging studies.

Prognosis left untreated: PAM is usually fatal if left untreated, with death occurring within 3-7 days after symptoms begin.

Treatment: Treatment for PAM typically involves a combination of antifungal and antibacterial medications, as well as supportive care, such as oxygen therapy and hydration.

Time to recover: The recovery time for PAM depends on the severity of the infection and the promptness of treatment. In some cases, recovery can take several weeks or even months.

Infographic and Stats: Here are some stats and an infographic about PAM:

  • PAM is extremely rare, with an estimated 40 cases reported in the United States between 1962 and 2021.
  • The majority of cases occur in young, healthy individuals who have been swimming in warm freshwater.
  • PAM has a mortality rate of over 97% if left untreated.
  • The average age of PAM patients is 13 years old, and the majority are male.

The infographic below shows the transmission, symptoms, diagnosis, and treatment of PAM.


Verified by: Dr.Diab (March 29, 2024)

Citation: Dr.Diab. (March 29, 2024). What is PAM, Incubation period, Early symptoms, Diagnosis. Medcoi Journal of Medicine, 4(2). urn:medcoi:article21303.

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