Table 2.

Summaries of studies on Ostreopsis sp. aerosols and health (n = 6/8).

Author	Location	Exposure assessment method	Population and study period	Measured outcome	Findings summary
Galitelli 2006	Coasts of Bari, Italy	Unusual proliferations of the Ostreopsis genus (more than 1 million cells/L) occurred during summers of 2003 and 2004.	28 patients (9 men, 18 women, and 1 child; mean age, 38.6 years; range, 10–68 years) were identified with symptoms occurring during recreational or working activities on the beach.	Rhinorrhoea; dry or mildly productive cough; fever; bronchoconstriction with mild dyspnoea and wheezing; conjunctivitis	The most common symptom was rhinorrhoea (100% of patients); cough (43%); fever (14%); and bronchoconstriction with mild dyspnoea and wheezes (43%). Conjunctivitis was also observed (11%). No hospitalization was required; some symptoms ceased within a few hours of exposure. Cough, fever, dyspnoea, and wheezing lasted up to 24 h. There was no relationship between symptoms and exposure duration or activities.
Bresciani 2007 & Durando 2007	Genova and La Spezia, Italy	After symptoms were reported, local environmental protection staff analysed air and water samples to exclude the presence of chemical pollution. After Ostreopsis was suspected as the causative agent, sea water from around five beaches were sampled for analysis during and after the outbreak; high densities of Ostreopsis ovata were detected. The analysis of water, plankton and macrophyte samples showed the presence of ‘putative palytoxin’.	Summers of 2005 and 2006	A case definition was constructed: presence at the seaside with an ongoing Ostreopsis ovata algal bloom; seeking medical care in a hospital emergency department; and presenting with at least two of the following symptoms: cough, dyspnoea, sore throat, rhinorrhoea, fever ≥38 °C, headache, lacrimation, nausea/vomiting and dermatitis. Patients who met the case definition were asked to provide detailed demographics, symptoms, time-activity, and baseline health data.	During the summer of 2015 in Genoa, a total of 209 patients (mean age 35.9 ± 20.1 years, range 1–89 years) met the case definition. Mean onset of symptoms was 4 h 33 min (median 7 h, range 30 min–23 h) after the beginning of exposure. For most, the symptoms stopped. Overall, 43 patients seeking medical help at the emergency departments needed hospitalization. The most frequent symptoms were fever (63.6%), sore throat (50.2%), cough (40.2%), and dyspnoea (38.8%). Samples for laboratory analysis were available during the acute phase in 82 patients (39.2%). Of these patients, 46.3% had leucocytosis, and 40.2% had neutrophilia. No other significant divergence from normal laboratory values (transaminases, gamma-glutamyl transpeptidase, creatinine and sedimentation rate) was found. All electrocardiogram and chest X-ray tests were negative. None of the examined risk variables regarding time activity patterns (e.g., distance from the sea, length of stay on the beach), demographics, or comorbidities were associated with hospitalization. During the following summer, along with new Ostreopsis algal blooms, 19 cases matching the above described case definition were identified by the surveillance network in both cities of Genoa and La Spezia. thought that only a few of these were caused by inhalation of aerosolised O. ovata fragments.
Vila 2008	Sant Andreu de Llavaneres, Catalonia, Spain	Seawater was sampled and cells were counted using microscope	62 people were interviewed for symptoms during outbreak; summer 2004.	Rhinorrhoea, nose irritation, throat irritation, coughing, expectoration, eye irritation, and migraine	The main symptoms were rhinorrhea (74.2%), nose irritation (66.1%), throat irritation (62.9%), coughing (59.7%), expectoration (51.6%), eye irritation (41.4%) and migraine (40.3%). The estimated period between exposure and symptoms was around 3 h, and the symptoms persisted for around 45 h. Symptoms increased during evenings.
Tichadou 2010	French Mediterranean coast	The French Mediterranean Ostreopsis Surveillance Network operates on an active basis during the blooming period from June 15 to September 15, which provides environmental monitoring by visual observation and testing of water samples; and a health vigilance system to detect suspected cases arising from direct contact or inhalation of contaminated water.	Between 2006 and 2009, nine blooms were observed, five of which led to 47 patients presenting symptoms.	Symptoms reported by affected, which included mild skin, mucosal, and/or respiratory irritations.	Ostreopsis blooms induce skin and respiratory disorders when human beings are exposed to saltwater with a high concentration of algal cells. Severe cases with prolonged exposures reported general flu-like symptoms, including headache, joint pain, vertigo, fever, fatigue, and diarrheal. Symptoms regressed without treatment within 12–72 h.
Illoul 2012	Beaches in Western area of Algiers Wilaya, Algeria	In July 2009, 9 samples were taken few days after the toxic event from five beaches. At 14 beaches, at least one monthly water sample was taken at each beach between August 2009 to February 2011 and cell abundance was measured using microscopy. To estimate the abundances of epiphytic Ostreopsis cells, macroalgae samples (red, brown and green algae) were occasionally taken in select beaches. To identify the Ostreopsis species, molecular analyses via PCR amplification were attempted on different water samples collected during a former summer sampling in 2008 and during the 2009 and 2010 blooms.	Approximately 300 patients reported symptoms during July 2009	Human respiratory intoxication episode registered during July 2009 in five beaches of the western area of Algiers Wilaya. Fever, rhinitis, conjunctivitis, cough and skin irritations were the most common clinical symptoms observed.	Relatively high levels of Ostreopsis were detected in the first samples taken a few days after the human intoxication event (19 and 22 of July 2009). Otherwise, Ostreopsis was also detected with abundances ranging from with period ranges from July to December 2009 and from April 2010 to January 2011. These values were generally lower than past values reported in the Northern Mediterranean. When macroalgae were sampled, Ostreopsis was also detected.
Vila 2016	Sant Andreu de Llavaneres, Catalonia, Spain	Water samples were taken at very shallow (about 20–50 cm) depths. Samples for the estimations of epiphytic Ostreopsis were collected from the macroalgae mat. Cell numbers in the water column and the mat were estimated from the samples via microscopy.	16 staff of a nearby indoor-outdoor restaurant directly exposed to marine aerosols at least 8 h daily from June to December 2013.	Ostreopsis-related symptoms reported by the cohort (e.g., eye irritation, nose irritation, rhinorrhoea, and general malaise) as measured by a questionnaire.	Throughout the bloom (June–October 2013), 81% of the human cohort experienced at least one Ostreopsis-related symptom. Symptoms lasted no longer than 3–4 days. The health effects were greatest in early August when the bloom transitioned from the exponential growth phase to the stationary phase. Negligible symptoms were reported from August to mid-October, which is the stationary period with persistently high cell concentrations. The O. cf. ovata epiphytic and planktonic cell populations exhibited similar patterns, with a peak in early August, then a stationary period from August to mid-October, and then a decrease.
Berdalet 2022	Sant Andreu de Llavaneres, Catalonia, Spain	Same sampling methods as Vila et al., 2016. Samples were taken once or twice per week in July and August, twice per month in June, September and October, and monthly in November and December. Additional samples were collected when necessary in the fall.	Restaurant staff and the nearby residents were invited to participate in epidemiological surveys. Between 5 and 29 surveys were answered each year.	Ostreopsis-related symptoms reported by the cohort grouped by organ systems (general, otorhinolaryngologic, ophthalmologic; digestive; respiratory; dermatologic; and cardiac) as measured by a daily questionnaire.	Over the 6 years, the prevalence rate of the symptoms varied over time – between 3.1% and 13.1% for malaise, 2.6% and 45.9% for runny nose, 2.3% and 9.7% for sore eyes, 0%–13.6% for headaches, and 0%–45.9% for nose irritation. Temporal patterns of reported health symptoms were observed, with highest rates coinciding with the early stationary phase of the blooms.
Chomeret 2022	Several beaches on the French Basque coast	Water samples and macroalgae samples were taken at beaches with reported cases. Observation and counts of cells were done by light microscopy and by fluorescence. Species were isolated and identified via sequencing and phylogenetic analysis. Toxins were screened for the presence of toxins (PLTX and related analogues) using LC-MS/MS analysis.	About 10 cases of respiratory symptoms in September 2020 were first reported by swimmers and beach visitors. In 2021, following an unusual outbreak of Ostreopsis in some of the beaches, 674 confirmed cases were reported.	Beach users reported various respiratory and cutaneous symptoms (e.g., difficulty breathing, irritations, headaches, dry cough, nose irritation, eye irritation and/or dermatitis, and general malaise) after direct contact with water and/or after inhalation of aerosols.	The symptoms disappeared within 2 days without a need to medicate when people moved away from the area concerned by the Ostreopsis bloom. Detection of presence of both O. cf. siamensis and O. cf. ovata, establishing the French Basque coast as a new Northern distribution limit. The presence of ovatoxins in the collected and cultivated samples confirmed toxicity and identified O. cf. ovata as the producer.