Aquatic Toxins Nursing CE Course

Signs and Symptoms 

Depending on the route of entry, V. vulnificus can cause three distinct infection presentations: primary septicemia, gastroenteritis, or wound infection. The ingestion of V. vulnificus can lead to gastroenteritis or primary septicemia. In primary septicemia, the portal into the bloodstream is thought to be through the small intestine or colon. Gastrointestinal (GI) symptoms are watery diarrhea, abdominal cramping, nausea, vomiting, fever, and chills and may be present with septicemia. Primary septicemia accounts for 45% to 60% of all cases and has a mortality rate of 50%. Symptoms can progress rapidly, and by the time medical intervention is sought, many patients present to the hospital already in shock or become profoundly hypotensive within 12 hours of admission. The mortality rate increases to over 90% when the patient is hypotensive at initial presentation (Haftel & Sharman, 2023; Morris, 2024).

V. vulnificus gastroenteritis presents with symptoms such as a sudden onset of diarrhea, nausea, vomiting, fever, and chills. Although most people recover from this type of infection, this presentation must be treated aggressively because the GI effects may precede and overlap with septicemia. GI presentation of infection accounts for 10% to 15% of all V. vulnificus infections. It usually resolves within 3 to 4 days without lasting effects (Haftel & Sharman, 2023; Morris, 2024).

In the case of wound infections, the bacteria enter the body through a preexisting laceration, puncture, or abrasion, and quickly colonize. This can occur through exposure of the open area to contaminated water, shellfish, or fish. This exposure initiates an intense skin reaction, including cellulitis with large blisters that can rapidly progress to necrotizing fasciitis with myonecrosis (fast-spreading, soft-tissue infection). Necrotizing fasciitis is commonly referred to as flesh-eating disease. It causes necrosis of the muscle fascia and subcutaneous tissue, and spreads rapidly. It is often life-threatening, requiring early diagnosis and aggressive treatment. Infection with V. vulnificus usually requires admission to an intensive care unit and limb amputation. The overall mortality rate of a patient who has V. vulnificus infection is 15% to 25%, with some patients dying within 1 to 2 days of becoming ill. The mortality rate increases to 54% in patients who have preexisting hepatic or immunosuppressive disease (Haftel & Sharman, 2023; Morris, 2024; Stevens & Baddour, 2024; Wallace & Perera, 2023).

Diagnosis

Consider a diagnosis of V. vulnificus if an infected wound has been recently exposed to salt or brackish water or if there are signs of septicemia following the consumption of shellfish. A wound or stool culture should be obtained based on patient presentation. Diagnostic confirmation of a V. vulnificus infection is based on the presence of the bacteria in the patient's wound, blood, or stool culture. Blood cultures are recommended for a febrile patient presenting with hemorrhagic bullae (blisters) or any other signs of sepsis. It is recommended that all V. vulnificus isolates be forwarded to the local public health laboratory (CDC, 2024c; Haftel & Sharman, 2023; Morris, 2024).

Treatment 

Supportive care is recommended for mild cases of gastroenteritis due to V. vulnificus. This includes oral fluid replacement for diarrhea, along with anti-diarrheal, antipyretic, analgesic, and antiemetic medications as needed. In more severe cases, IV fluids may be required for fluid replacement. Fluid intake, urine output, electrolyte levels, and renal function should be monitored closely (CDC, 2024c; Haftel & Sharman, 2023; Morris, 2024).

Treatment must be initiated promptly for more severe cases, as antibiotics have been shown to improve mortality rates. Wound infections must be thoroughly assessed. Rapid debridement and fasciotomy should be performed if indicated to control the infection and prevent the need for limb amputation. Patients who present with septic shock should receive antibiotic therapy and prompt and aggressive resuscitative efforts following facility sepsis protocols. If antibiotic treatment is delayed beyond 72 hours, the mortality rate for patients is 100% (Haftel & Sharman, 2023; Morris, 2024).

Susceptibility reports have shown that third- and fourth-generation cephalosporins, tetracyclines, carbapenems, fluoroquinolones, sulfa-trimethoprim (Bactrim), piperacillin-tazobactam (Zosyn), and aminoglycosides are all effective against V. vulnificus. For the best outcomes, combination therapy is recommended. For adults, a third-generation cephalosporin (e.g., cefotaxime [Claforan] 2 g IV every 6 to 8 hours or ceftriaxone [Rocephin] 1 to 2 g IV daily) combined with either a fluoroquinolone (e.g., ciprofloxacin [Cipro] 750 mg orally twice daily) or tetracycline (doxycycline [Vibramycin, Doryx] 100 mg orally twice daily or minocycline [Solodyn, Minocin] 100 mg orally twice daily) have been used successfully. When treating children, a third- or fourth generation cephalosporin (e.g., ceftriaxone [Rocephin] 50 to 75 mg/kg IV daily, maximum 2 g/day or cefotaxime [Claforan] 50 mg/kg IV every 6 to 8 hours, maximum 8 g/day) plus minocycline (Minocin) 2 mg/kg by mouth every 12 hours, maximum 100 mg/dose, is recommended due to the contraindication for doxycycline (Vibramycin, Doryx) and fluoroquinolones such as ciprofloxacin (Cipro) within this age group. For topical infections, silver sulfadiazine can be applied to cover the wound. Although these recommendations are best practices, antibiotic resistance has recently been found in 50% of V. vulnificus infections (Haftel & Sharman, 2023; Morris, 2024).

Prevention 

The CDC (2024j) provides strategies nurses can share with patients to protect them from V. vulnificus infections. Patient education should include the following:

• Avoid brackish or salt water with an open wound. If entering brackish or salt water with an open wound, the area should be covered with a waterproof bandage to prevent direct contact with the water.
• Wounds should also be covered if handling raw seafood or the juices from raw seafood (for example, when working in the restaurant and fishing industries).
• If a wound comes into contact with brackish or salt water, raw seafood, or the juices from raw seafood, it should be washed immediately with soap and water.
• If a skin infection or sensitivity develops, seek treatment quickly and alert the healthcare provider (HCP) that exposure to salt water or raw seafood has occurred.
• Avoid eating raw or undercooked oysters or other shellfish.
• Wash hands after handling raw seafood (CDC, 2024j; Schwartz, 2025).

The nurse should remind all patients who have a chronic disease or immunocompromised state to avoid eating raw seafood, especially raw oysters. This is essential education for any patient who is immunocompromised (e.g., liver disease, diabetes, malignancies, HIV, kidney disease), as these patients are highly susceptible to infection, accounting for 80% to 90% of all cases presenting with primary sepsis (Haftel & Sharman, 2023; Morris, 2024).

Freshwater Amoeba

Naegleria fowleri

Naegleria fowleri is a free-living, thermophilic (heat-loving), microscopic amoeba (single-celled organism) commonly found in warm bodies of fresh water, including lakes, rivers, and hot springs. It infects an individual when contaminated water enters the nose. After N. fowleri enters the nasal passageway, it travels to the brain. Once in the brain, it causes primary amebic meningoencephalitis (PAM), which is how it came to be known as the "brain-eating amoeba." Since N. fowleri prefers warm bodies of water, it is commonly found in Florida and other southern states with warm climates. N. fowleri is the only Naegleria species known to infect humans. Infection often occurs when people engage in water activities in fresh water, such as swimming or diving. Infection can occur from other contaminated sources of fresh water, such as swimming pools that are inadequately chlorinated or tap water, although it is less likely. It is important to note that the amoeba can only cause infection when it enters the body through the nasal passage. Infection cannot occur by ingesting contaminated water orally. This amoeba has a specific life cycle (refer to Figure 1) that affects transmission and subsequent disease (CDC, 2024f, 2025a; Minnesota Department of Health, 2024; North Carolina Department of Health and Human Services [NCDHHS], 2024).

Figure 1

The Life Cycle of Naegleria fowleri 

(CDC, 2024f)

PAM has been identified in Florida since the early 1960s, and new cases have also emerged in other states such as Texas, California, Arizona, and South Carolina. Overall, PAM infections have occurred in 19 US states, including Indiana, Minnesota, and Maryland. Infection with N. fowleri is most common during July, August, and September, when water temperatures rise. N. fowleri grows best in water or soil between 86° F (30° C) and 113° F (45° C). Consecutive hot days cause higher water temperatures, decreased water levels, and an increased number of people who engage in freshwater activities. There were 157 documented cases of PAM in the United States between 1962 to 2022. One series of accurately documented cases in the United States revealed that of the infections, 62% were in children and over 75% were in those assigned male at birth (with a median age of 12 years; CDC, 2025a; Florida Health, 2023; Gharpure et al., 2021; Minnesota Department of Health, 2024; Pana et al., 2023; Seas & Bravo, 2024).

The trophozoite state (the feeding stage of a protozoan parasite) is sensitive to environmental changes, including temperature, while the cysts are much more tolerant of changes to their environment. The trophozoites are killed quickly by even short periods of cool temperatures, but the cysts can survive the cold for weeks to months. This provides an opportunity for the amoeba to be found in almost any lake or river and eliminates most methods of controlling the natural levels of this parasite. One thing that makes the cysts nonviable is drying them out. Chlorine and chloramine also kill N. fowleri trophozoites and cysts. The amoeba does not survive in salt water and has not been detected in the ocean (CDC, 2025a; Seas & Bravo, 2024).

Outcomes

Unfortunately, most cases of PAM end in death within 5 days of the appearance of symptoms. The mean time from the onset of symptoms to death is 5.3 days, with a range of 1 to 12 days. The mean time from exposure to death is 9.9 days, with a range of 6 to 17 days. Out of the 157 cases in North America, all but 5 were fatal. The five documented survivors in North America include four in the United States and one in Mexico (CDC, 2025a; Pana et al., 2023).

Signs and Symptoms 

A patient exposed to N. fowleri presents with symptoms of PAM within 1 to 9 days. Early symptoms include severe headache, fever, nausea, and vomiting. Later symptoms include a stiff neck, confusion, loss of balance, photophobia, seizures, hallucinations, and cranial nerve deficits. Focal deficits and meningeal signs are typically present upon examination, and occasionally nasal discharge, nasal obstruction, and smell and taste abnormalities are present. The signs and symptoms of PAM can mimic acute bacterial meningitis, especially in the early stage. Disease progression is swift, leading to coma and eventually death. Once an autopsy is performed, the findings often include hemorrhagic necrosis of the olfactory bulbs (explaining the smell and taste abnormalities) and the cerebral cortex (CDC, 2024a; Minnesota Department of Health, 2024; Pana et al., 2023; Seas & Bravo, 2024).

Diagnosis

To diagnose PAM, cerebrospinal fluid (CSF) must be obtained with a lumbar puncture. A diagnosis of PAM is confirmed if N. fowleri is visualized in the fresh, unfrozen, unrefrigerated CSF sample under a microscope. Since the amoeba cannot tolerate cold temperatures, freezing or refrigerating the sample will kill it. To aid with quick detection, a polymerase chain reaction (PCR) from the CSF can identify the deoxyribonucleic acid (DNA) of N. fowleri. Diagnosis can also be made by examining tissue from a brain biopsy or autopsy specimen. Serology testing is still only considered a research technique and has not been evaluated for use as a routine diagnostic tool. The CDC requests that specimens with fresh CSF, tissue obtained from the brain, or formalin-fixed and paraffin-embedded tissue be sent to them for diagnostic confirmation (CDC, 2025a; Pana et al., 2023; Seas & Bravo, 2024).

Treatment

The optimal treatment of PAM is unknown due to the rapid symptom progression and high mortality rate. Current treatment recommendations are based on the regimens used in the few cases of survivors and include:

• amphotericin B (AmBisome), 1.5 mg/kg/day IV in 2 divided doses for 3 days, then 1 mg/kg/day IV once daily for the next 11 days
• intrathecal amphotericin B (AmBisome) 1.5 mg once daily for 2 days, then 1 mg/day every other day for 8 days
• azithromycin (Zithromax) 10 mg/kg/day IV or PO daily for 28 days
• fluconazole (Diflucan) 10 mg/kg/day IV or PO daily for 28 days
• rifampin (Rifadin, Rimactane) 10 mg/kg/day IV or PO daily for 28 days
• miltefosine (Impavido) 50 mg PO twice daily for patients who weigh less than 45 kg or 50 mg PO 3 times daily for patients who weigh over 45 kg with a maximum dose of 2.5 mg/kg/day for 28 days
  • Miltefosine (Impavido) is an antiparasitic that is mildly nephrotoxic, so dosing should be adjusted for individuals who have renal conditions. However, there is an increased risk of mortality with reduced doses, so the risk of nephrotoxicity should be balanced with the risk of dose reduction when deciding on treatment.
• dexamethasone (Decadron) 0.6 mg/kg/day IV in 4 divided doses for 4 days (CDC, 2025a)

The CDC suggests that any HCP caring for a patient who has suspected PAM or other amoeba infection contact the CDC Emergency Operations Center at 770-488-7100 to consult with experts in managing these patients as they can provide diagnostic assistance, specimen collection guidance, shipping instructions, and treatment recommendations (CDC, 2025a).

Prevention 

The only way to eliminate the risk of exposure to N. fowleri and prevent PAM is to not participate in freshwater activities and never put contaminated tap water into the nasal passageway (e.g., using tap water for nasal irrigation). Since this is not always possible, nurses can educate patients on prevention strategies to protect them from N. fowleri (Minnesota Department of Health, 2024; NCDHHS, 2024). Patient education should include the following information regarding taking part in water-related activities in bodies of warm fresh water.

• Avoid entering the water if the water temperature is high and the water level is low.
• Avoid submerging your head underwater.
• Pinch your nose shut or use nose clips to keep it closed while in the water.
• Avoid activities that can stir up sediment from the bottom of the water source (Florida Health, 2023; Minnesota Department of Health, 2024; NCDHHS, 2024; Pana et al., 2023).

Patient education on safely using water for nasal irrigation should include the following.

• Use only distilled or sterile water.
• If tap water must be used, boil for at least 1 minute (3 minutes if at an elevation above 6,500 ft) and cool before use, or filter the water using a filter with a pore size of less than 1 micron that is designed to remove aquatic toxins.
• Rinse all devices used with safe water (distilled, sterile, filtered, or boiled) and allow them to air dry completely (Florida Health, 2023; Minnesota Department of Health, 2024).

Algal Blooms 

Algae are organisms that live in aquatic environments (both fresh water and salt water) and produce energy through photosynthesis, just like plants. Algae naturally help to sustain marine life as part of the food chain. However, when the conditions are right, microscopic algae can grow unimpeded and over-populate. HABs have affected all 50 states, as well as Puerto Rico and the US Virgin Islands. The optimal conditions for this extreme growth are warm water and increased nutrients from fertilizers or sewage introduced into the water through runoff. Increased temperatures cause significantly more algal blooms. A 30-year review by the US Environmental Protection Agency (EPA) revealed that reservoirs in Indiana, Kentucky, and Ohio have been warming earlier in the year, remaining warm for longer amounts of time, and experiencing more frequent blooms. This aligns with climate change science, which suggests that prolonged warmer temperatures promote the growth of cyanobacteria, also known as blue-green algae, and leads to more severe blooms. Cyanobacteria are the main contributors to blooms in fresh water, with over 90% of these blooms occurring in freshwater environments such as lakes and reservoirs. Other parameters such as salinity, water flow, rainfall, wind speed, and wind direction can impact how the bloom increases in size, where it forms, and how it moves to expose humans and animals. Evidence suggests that increased carbon dioxide (CO2) and reduced water pH can exacerbate blooms and increase their toxicity. As a result, algal blooms and their associated health and environmental impacts are a growing concern. When overgrowth occurs, the algae form a foam or scum-like mass known as an algal bloom. Wind, waves, currents, or tides can move these blooms around. They release toxins into the ecosystem, making people and animals sick. When this occurs, the algae bloom is known as an HAB (CDC, 2023, 2024k; Florida Health, 2025; National Institute of Environmental Health Sciences [NIEHS], 2025; EPA, 2025b).

In most cases, HABs are short-lived, occur in late summer to early fall along the coast of a body of water, and vary in size and severity. Some HABs emit a foul odor due to the hydrogen sulfide gas from decomposition within the bloom. The smell is described as comparable to rotten eggs, causing most people to avoid it whenever possible. People can get sick from HABs by eating contaminated fish, swimming, or drinking contaminated water. Unfortunately, cooking contaminated fish does not destroy the toxin, and boiling contaminated water only concentrates the toxin (Florida Health, 2025; NIEHS, 2025).

Cyanobacteria

In fresh bodies of water, HABs are typically caused by cyanobacteria (also known as blue-green algae). This type of algae is a single-celled organism known as phytoplankton. Some cyanobacteria produce toxins called cyanotoxins. These toxins are either released from the cell during cell death or lysis or are continuously released into the water without cell death. The blue-green algae blooms are primarily blue, bright green, brown, or red, and have an odor like rotting plants. Pets can become sick from exposure and should be kept away from contaminated fish or water (CDC, 2024b, 2024d, 2024h, 2024l; EPA, 2025a).

Exposure to the toxins produced by cyanobacteria occurs through three routes: skin contact, inhalation, or ingestion. The toxins mix with water droplets and spray and become aerosolized, allowing humans and animals to inhale them. Ingestion can occur through eating or drinking water or food that is contaminated. It is more difficult for the toxins to pass through the skin. However, skin exposure can cause topical irritation or rashes after swimming or bathing in contaminated water. The extent of the irritation depends on exposure length (CDC, 2024d, 2024h, 2024l; EPA, 2025a, 2025b). Table 1 shows the side effects of specific cyanotoxins.

Table 1

Cyanotoxins and Their Health Effects on Humans 

(CDC, 2024h; EPA, 2025a, 2025b)

Many people will present with coughing and eye irritation near the HAB, and symptoms may subside upon leaving the area. In addition to the specific type of cyanotoxin exposure, increased exposure time and comorbidities of the patient lead to more severe symptoms (CDC, 2024d, 2024h, 2024l).

Diagnosis

Early identification of patient exposure to an HAB can aid the HCP in the diagnosis and guidance for potential treatment. Other illnesses with similar symptoms (i.e., organophosphate poisoning, mushroom poisoning, drug overdose, chemical burn, and acetaminophen toxicity) should be ruled out to ensure an accurate diagnosis. There are no specific routine diagnostic tests recommended for cyanobacteria (CDC, 2024a, 2024d, 2024g, 2024h). Laboratory tests that may be performed to aid in the diagnosis, along with patient history, include:

• electrolytes and liver function tests: BMP, ALT, AST
• renal function tests: BUN and creatinine
• serum glucose
• urine to check for proteinuria and glycosuria (severe toxicity)
• chest x-ray in patients presenting with respiratory symptoms (CDC, 2024a, 2024g)

Only specialized laboratories can perform confirmatory lab tests for cyanobacteria and cyanotoxins in feces, urine, GI contents, tissues, blood, and water specimens (CDC, 2024h).

Treatment

There is no antidote for cyanobacterial toxins. Treatment is primarily supportive and focuses on symptom management. The type of treatment used is dependent on the route of exposure. Treatment for respiratory symptoms following inhalation often includes antihistamines and steroids. If there are no contraindications and the patient seeks professional help within 1 to 2 hours of ingestion, the patient can be treated with activated charcoal. If GI symptoms appear, antiemetic or antidiarrheal medications can be used to control nausea, vomiting, and diarrhea. Intravenous fluid administration may be needed to replace lost fluids and electrolytes. Following eye exposure, contact lenses must be removed and the eyes irrigated for at least 15 minutes with normal saline. Follow-up with an ophthalmologist is suggested if symptoms persist after irrigation. After skin exposure, contaminated clothing and jewelry should be removed, and the skin should be washed with soap and water for 10 to 15 minutes. Topical antihistamines can be used for cutaneous reactions (CDC, 2024g, 2024h).

Patient Education 

Patient education related to cyanobacteria exposure should include the following.

• Avoid HAB-contaminated waters. Check local swimming and fishing advisories before visiting lakes and rivers.
• Stay out of the water if it has a foul odor; appears discolored; has foam, scum, or paint-stroke-like lines on the surface; or has multiple dead fish or animals along the shoreline.
• Do not boil water that contains cyanobacterial toxins.
• Do not fill pools with water from a lake, river, or pond.
• Avoid eating large reef fish (e.g., grouper), especially the head, gut, liver, or eggs.
• When fishing or collecting shellfish for consumption, check local shellfish and fish advisories before ingesting the seafood.
• Following exposure to contaminated waters, wash exposed areas with soap and water, follow up with an HCP, call the poison control center hotline, and report the illness to the local and state health departments.
• Pets who have been exposed to toxins from drinking contaminated water or eating contaminated marine animals require prompt veterinarian treatment as they can quickly become severely ill (CDC, 2024g, 2024i; Florida Health, 2025).

Red Tide

Like freshwater HABs, those found in saltwater are caused by phytoplankton, most commonly diatoms and dinoflagellates. Saltwater HABs are known as red tides. The most common type in the United States is Karenia brevis blooms, which appear dark red or brown and occur most frequently in the Gulf of Mexico. The toxin produced by K. brevis is brevetoxin, a tasteless, odorless, neurotoxic compound that can cause toxicity through inhalation, ingestion, or dermal exposure. The most common transmission route of K. brevis is through contaminated shellfish. However, patients can also be exposed to the red tide algae blooms through exposure to the contaminated water (CDC, 2025b; Florida Health, 2025).

Symptoms 

Exposure to the HAB can induce red tide tickle, an illness characterized by a scratchy throat and cough secondary to breathing in airborne brevetoxins. These toxins are released into the air when the wind or waves break open the algae cells. Healthy individuals can develop respiratory symptoms rapidly after exposure to HAB. In addition to red tide tickle, other respiratory symptoms have been reported, including shortness of breath, sneezing, eye irritation, and nasal irritation. Exposure to brevetoxins can induce an acute exacerbation for those who have chronic respiratory conditions such as asthma and chronic obstructive pulmonary disease (COPD). Consuming toxins from contaminated fish or shellfish can cause illness marked by GI symptoms, such as abdominal pain, nausea, vomiting, and diarrhea, as well as neurological symptoms, such as tingling in the mouth and tongue, vertigo, ataxia, altered temperature perception, and slurred speech. In severe cases, these neurological symptoms may progress to partial paralysis (CDC, 2024b, 2024d, 2025b; Marcus, 2024; Florida Health, 2025).

Diagnosis

Symptomatic evaluation with a history of potential patient exposure to brevetoxin can aid the HCP in determining the diagnosis. Laboratory verification can be achieved by detecting brevetoxins or their metabolites in a urine specimen through immunoassay (CDC, 2024e, 2025b).

Treatment

Following physical contact with brevetoxins, it is advised to immediately wash the contaminated area with soap and water. For rashes or skin irritation, a topical steroid such as hydrocortisone (Dermacort) cream may be used to decrease the symptoms. Those who have persistent respiratory symptoms can be advised to take over-the-counter antihistamines. For more severe or persistent symptoms, patients should be evaluated and treated with systemic steroids, bronchodilators, oxygen, or other supportive therapy to ensure the patency of the airways (CDC, 2024g; Florida Health, 2025).

Protection from Aquatic Toxins

The HCP can offer education to avoid exposure to toxins within waterways in the local environment. The primary way to prevent exposure to aquatic toxins is to avoid fresh and salt water where algal blooms are present. Pets should also be protected and kept away from contaminated water. If exposure occurs, they should not be allowed to lick their fur until the toxin is washed out with soap and water. When visiting state or local waterways, patients should be encouraged to review official health department reports and adhere to any warnings or local conditions that would direct activities in the water. If there is a notification of harmful algae in the public drinking water supply, all local or state guidelines should be followed to minimize risks. Finally, patients should avoid eating any seafood that may be contaminated by HABs and their toxins (CDC, 2024i, 2024j, 2025a).

The CDC reports that people can be exposed to HAB toxins up to 4 miles inland from a contaminated water source. Since marine HAB can cover hundreds of square miles, the toxins can impact boaters, homeowners, residents, and tourists. Unfortunately, the only way to avoid exposure is to stay out of the affected area, which can be difficult for those who work or live in the area. For aerosolized toxins, the use of particle filter masks outdoors can decrease exposure. For those who live near the HAB, remaining indoors and using air conditioning instead of opening windows can reduce the severity of respiratory symptoms. Ingestion can be prevented by avoiding raw seafood, especially oysters and other shellfish. Not only can shellfish and marine animals living directly in the HAB be contaminated by the toxins, but larger fish or animals that feed on these fish may be exposed. Fish tested following exposure to blue-green algae have demonstrated that there is not a high accumulation of cyanotoxins in the edible parts, but there may be a high level in the organs (CDC, 2024j, 2025a; Florida Health, 2025; Marcus, 2024; NCCOS, 2025; Yuan et al., 2024).

Tap water can contain HAB toxins, but this is uncommon, even in areas with high levels of toxins. There are currently no federal guidelines regarding acceptable levels of cyanobacteria or cyanotoxins in public drinking water. Exposure can also occur through health care facilities, but this risk remains very low. Nutritional supplements that contain algae could pose a risk for exposure to HAB toxins. During algae harvesting to produce supplements, toxin-producing cyanobacteria could accidentally be included, leading to contamination (CDC, 2024i, 2024j; EPA, 2025a).

Preventing Algal Blooms from Forming

As with all health concerns, prevention is preferred over treatment. There are large-scale multidisciplinary efforts across the United States to reduce the incidence of HABs. Experts in oceanography, engineering, human health, and ecology are coming together to enhance knowledge and practice through research, environmental monitoring, forecasting and predicting, and mitigation strategies. Mitigation strategies include flocculation (spraying clay over bloom to bind and remove toxins); use of algaecides; investigation into destroying HAB cells through nano-sized, ozone-filled bubbles; and finding other ways to decrease the amount of nitrogen and phosphorus polluting our waterways. Those in agriculture often use biological controls, but the proposed use of the Ameobophyra parasite is not accepted due to a lack of research and concerns regarding unintentional impact on the environment (National Oceanic and Atmospheric Administration [NOAA], n.d.; US National Office for Harmful Algal Blooms, n.d.; Woods Hole Oceanographic Institute, 2022). Suggestions to individuals to support preventive initiatives include the following.

• Use only recommended quantities of fertilizer on individual lawns to reduce the runoff going into local waterways, as fertilizer runoff may provide algae the nutrients needed to flourish.
• Maintain septic systems to prevent wastewater leakage into nearby waterways, as wastewater is a rich source of nutrients for algae (NOAA, n.d.).

References

Centers for Disease Control and Prevention. (2023). Harmful algal blooms threaten our health, environment, and economy. https://www.cdc.gov/harmful-algal-blooms/media/pdfs/Algal-Bloom-Brief-508.pdf

Centers for Disease Control and Prevention. (2024a). Clinical and laboratory diagnosis for Naegleria fowleri infection. https://www.cdc.gov/naegleria/hcp/diagnosis-testing/index.html

Centers for Disease Control and Prevention. (2024b). Clinical overview of harmful algal bloom-associated illnesses. https://www.cdc.gov/harmful-algal-blooms/hcp/clinical-overview/

Centers for Disease Control and Prevention. (2024c). Clinical overview of vibriosis. https://www.cdc.gov/vibrio/hcp/clinical-overview/index.html

Centers for Disease Control and Prevention. (2024d). Clinical signs and symptoms of harmful algal bloom-associated illnesses. https://www.cdc.gov/harmful-algal-blooms/hcp/clinical-signs/index.html

Centers for Disease Control and Prevention. (2024e). Clinical testing guidance for illnesses caused by saltwater harmful algal blooms. https://www.cdc.gov/harmful-algal-blooms/hcp/diagnosis-testing/clinical-testing-saltwater-harmful-algal-blooms.html

Centers for Disease Control and Prevention. (2024f). Free living amebic infections [image]. https://www.cdc.gov/dpdx/freeLivingAmebic/index.html

Centers for Disease Control and Prevention. (2024g). Patient care for illnesses caused by harmful algal blooms. https://www.cdc.gov/harmful-algal-blooms/hcp/clinical-care/index.html

Centers for Disease Control and Prevention. (2024h). Physician reference for cyanobacterial blooms. https://www.cdc.gov/harmful-algal-blooms/communication-resources/physician-reference-for-cyanobacterial-blooms.html

Centers for Disease Control and Prevention. (2024i). Preventing illnesses caused by harmful algal blooms. https://www.cdc.gov/harmful-algal-blooms/prevention/

Centers for Disease Control and Prevention. (2024j). Preventing Vibrio infection. https://www.cdc.gov/vibrio/prevention/

Centers for Disease Control and Prevention. (2024k). Summary report—One Health Harmful Algal Bloom System (OHHABS), United States, 2022. https://www.cdc.gov/ohhabs/data/summary-report-united-states-2022.html

Centers for Disease Control and Prevention. (2024l). Symptoms of illnesses caused by freshwater harmful algal blooms. https://www.cdc.gov/harmful-algal-blooms/signs-symptoms/symptoms-freshwater-harmful-algal-blooms.html 

Centers for Disease Control and Prevention. (2025a). Clinical care of Naegleria fowleri infection. https://www.cdc.gov/naegleria/hcp/clinical-care/

Centers for Disease Control and Prevention. (2025b). Clinical signs and symptoms caused by saltwater harmful algal blooms. https://www.cdc.gov/harmful-algal-blooms/hcp/clinical-signs/symptoms-saltwater-harmful-algal-blooms.html

Florida Health. (2023). Primary amebic meningoencephalitis (PAM). https://www.floridahealth.gov/diseases-and-conditions/primary-amebic-meningoencephalitis/index.html

Florida Health. (2025). HABs: Harmful algae blooms. https://www.floridahealth.gov/environmental-health/aquatic-toxins/harmful-algae-blooms/index.html

Gharpure, R., Bliton, J., Goodman, A., Ali, I. K. M., Yoder, J., & Cope, J. R. (2021). Epidemiology and clinical characteristics of primary amebic meningoencephalitis caused by Naegleria fowleri: A global review. Clinical Infectious Diseases, 73(1), e19–e27. https://doi.org/10.1093/cid/ciaa520

Haftel, A., & Sharman, T. (2023). Vibrio vulnificus infection. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK554404/

Lavery, A. M., Backer, L. C., Roberts, V. A., DeVies, J., & Daniel, J. (2021). Evaluation of syndromic surveillance data for studying harmful algal bloom-associated illnesses—United States, 2017–2019. Morbidity and Mortality Weekly Report, 70(35), 1191–1194. https://www.cdc.gov/mmwr/volumes/70/wr/mm7035a2.htm?s_cid=mm7035a2

Marcus, E. N. (2024). Overview of shellfish, pufferfish, and other marine toxin poisoning. UpToDate. Retrieved April 3, 2025, from https://www.uptodate.com/contents/overview-of-shellfish-pufferfish-and-other-marine-toxin-poisoning

Minnesota Department of Health. (2024). Naegleria fowleri and primary amebic meningoencephalitis. https://www.health.state.mn.us/diseases/naegleria/index.html

Morris, J. G. (2024). Vibrio vulnificus infection. UpToDate. Retrieved April 2, 2025, from https://www.uptodate.com/contents/vibrio-vulnificus-infection

National Centers for Coastal Ocean Science. (2025). Harmful algal blooms: NOAA state of the science fact sheet. https://coastalscience.noaa.gov/news/hab-noaa-fact-sheet/

National Institute of Environmental Health Sciences. (2025). Algal blooms. https://www.niehs.nih.gov/health/topics/agents/algal-blooms/index.cfm

National Oceanic and Atmospheric Administration. (n.d.). Harmful algal blooms: Tiny organisms with a toxic punch. Retrieved April 2, 2025, from https://oceanservice.noaa.gov/hazards/hab/

North Carolina Department of Health and Human Services. (2024). Primary amebic meningoencephalitis. https://epi.dph.ncdhhs.gov/cd/diseases/pam.html

Pana, A., Vijayan, V., & Anikumar, A. C. (2023). Amebic meningoencephalitis. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK430754/

Schechinger, A. (2020). The high cost of algae blooms in US waters: More than $1 billion in 10 years. Environmental Working Group (EWG). https://www.ewg.org/research/high-cost-of-algae-blooms/

Schwartz, R. A. (2025). Vibrio vulnificus infection treatment & management. https://emedicine.medscape.com/article/1055523-treatment

Seas, C., & Bravo, F. (2024). Free-living amebas and Prototheca. UpToDate. Retrieved April 2, 2025, from https://www.uptodate.com/contents/free-living-amebas-and-prototheca

Stevens, D. L., & Baddour, L. M. (2024). Necrotizing soft tissue infections. UpToDate. Retrieved April 2, 2025, from https://www.uptodate.com/contents/necrotizing-soft-tissue-infections

US Environmental Protection Agency. (2025a). Harmful algal blooms (HABs) in water bodies. https://www.epa.gov/habs

US Environmental Protection Agency. (2025b). What are the effects of HABs. https://www.epa.gov/cyanohabs/health-effects-cyanotoxins

US National Office for Harmful Algal Blooms. (n.d.). Control and treatment. Retrieved April 3, 2025, from https://hab.whoi.edu/response/control-and-treatment/

Wallace, H. A., & Perera, T. B. (2023). Necrotizing fasciitis. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK430756/

Woods Hole Oceanographic Institution. (2022). Harmful algal blooms, understanding the threat and the actions being taken to address it. https://www.whoi.edu/wp-content/uploads/2022/01/2022WHOI-HarmfulAlgalBlooms-Report.pdf

Yuan, K.-K., Li, H.-Y., & Yang, W.-D. (2024). Marine algal toxins and public health: Insights from shellfish and fish, the main biological vectors. Marine Drugs, 22(11), 510. https://doi.org/10.3390/md22110510

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