how are humans affected by it?
By ingesting improperly harvested shellfish, breathing in aerosolized brevetoxins and in some cases skin contact.
Red tide
Humans are affected by the red tide species by ingesting improperly harvested shellfish, breathing in aerosolized brevetoxins (i.e. PbTx or "Ptychodiscus" toxins) and in some cases skin contact. 
how many inches of rain did hurricane allison bring to houston Over 40 inches. when did this happen? June 4, 2001. which places were affected by it? Texas to the Mid-Atlantic was effected. what damages did it cause? Approximately $8.5 billion in damage and killed 41 people. from which water body did it form? Gulf of Mexico. what is this waterbody? It is an ocean basin and a marginal sea of the Atlantic Ocean. what are its geological features? Its eastern, northern, and northwestern shores lie along the US states of Florida, Alabama, Mississippi, Louisiana, and Texas. has it faced any problems regarding leaking of oil? "Ixtoc I" oil platform in the Bay of Campeche suffered a blowout leading to a catastrophic explosion, which resulted in a massive oil spill. has it also faced any natural hazard? There are frequent "red tide" algae blooms. what is this tide? It is a common name for algal blooms, which are large concentrations of aquatic microorganisms, such as protozoans and unicellular algae. what may be the reasons behind this? The upwelling of nutrients from the sea floor, often following massive storms, provides for the algae and triggers bloom events. is it found along the beaches of america? UNANSWERABLE
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Red tide [SEP] Human exposure
Humans are affected by the red tide species by ingesting improperly harvested shellfish, breathing in aerosolized brevetoxins (i.e. PbTx or "Ptychodiscus" toxins) and in some cases skin contact. The brevetoxins bind to voltage-gated sodium channels, important structures of cell membranes. Binding results in persistent activation of nerve cells, which interferes with neural transmission leading to health problems. These toxins are created within the unicellular organism, or as a metabolic product. The two major types of brevetoxin compounds have similar but distinct backbone structures. PbTx-2 is the primary intracellular brevetoxin produced by "K. brevis" blooms. However, over time, the PbTx-2 brevetoxin can be converted to PbTx-3 through metabolic changes.