Exposure-response relationship between K. brevis blooms and reporting of upper respiratory and neurotoxin-associated symptoms

In southwest Florida, Karenia brevis (K. brevis) blooms occur frequently, can be very intense and persist over several years. Individuals living in coastal communities around the Gulf of Mexico are particularly vulnerable to brevetoxins released by K. brevis in seawater and carried inland within marine aerosol. Exposure to K. brevis occurs during residential, recreational, and occupational activities and has been associated with upper respiratory tract (URT) symptoms in healthy and medically vulnerable individuals. Additionally, ingestion of brevetoxin-contaminated seafood causes neurotoxic shellfish poisoning (NSP), and severe headaches prompting emergency department visits which occur in excess during K. brevis blooms. The current study examined a dose-response relationship between K. brevis in coastal waters and URT and NSP-like symptoms and headaches among southwest Florida residents. Data on past medical history (PMH) and medical symptoms were collected from the participants (n = 258) in five southwest Florida counties between June 2019 to August 2021. A dose-response relationship was observed between K. brevis blooms and reporting of URT and NSP-like symptoms and headaches. Reporting of NSP-like symptoms was higher among participants with a PMH of migraines, chronic fatigue syndrome (CFS) and mild memory loss, while the association of headaches with K. brevis blooms was accentuated among individuals with a PMH of migraines. These results suggest further investigations into the threshold of aerosolized brevetoxin dose required to elicit URT, headaches and/or NSP-like symptoms. These symptoms ultimately cause significant public health safety concerns, primarily among vulnerable populations with preexisting neurological conditions.

High Training Volumes are Associated with a Low Number of Self-Reported Sick Days in Elite Endurance Athletes

It has been proposed that high exercise loads increase the risk of infection, most frequently reported as upper respiratory tract infections, by suppressing the immune system. Most athletes will not train when experiencing sickness due to the fear of health complications. However, high training volumes are incompatible with high rates of non-training days, regardless of the cause. The purpose of this observational study was to examine the relationship between self-reported, exercise-constraining days of sickness (days when the athlete decided not to train due to symptoms of disease, either self-reported or by a physician) and the volumes of exercise training in elite endurance athletes by analyzing data from training logs kept for several years. The subjects included 11 elite endurance athletes (8 male, 3 female) competing at national and international levels in cross-country skiing, biathlon and long-distance running. Training logs available from these 11 subjects added to a total of 61 training years. The number of training hours per year (462, 79-856; median, range) was significantly and negatively correlated to the reported number of days not training due to sickness (15, 0-164) by a 3(rd) degree polynomial regression (R(2) = 0.48, F ratio = 18, p < 0.0001). We conclude that elite endurance athletes can achieve high training volumes only if they also experience few sick-days. Key pointsTop level performance demands high training volumes and intensities, which may compromise immune function.Elite athletes must have an immune system capable of intact function also when under sever physiological and psychological stress.Elite performance, especially in endurance sports, is therefore incompatible with a high rate of infections.A negative correlation between infections and exercise training load among elite athletes is consequently observed - the less sick you are the more you can train.