Freye et al. 2001. Investigators in New England studied regional aerobiology during the El Nino year of 1998, compared to 1997 and 1999 which were non-El Nino years.  It was found that max pollen and mold concentrations were higher and occurred earlier in the year for 1997.  In addition, there was an increase in ER visits for asthma, allergic rhinitis, and sinusitis during the spring of that year.