Scientists seeing more West Nile cases earlier in the year

(CNN)– Scientists are seeing a scary trend, more West Nile cases earlier in the year.

About one thousand Americans are hospitalized each year with the most severe form of the virus.

Another 15 hundred are diagnosed with the mosquito-borne disease.

Mild cases usually have broad symptoms like a fever, rash, and joint pain.

Many recover without treatment.

This year, West Nile activity picked up earlier than the normal, which is unusual in August and September.

Experts worry an early start could be a blockbuster year for the virus.