Many schools in the US require you to obtain health insurance beforehand. Many times students can find a very cheap health insurance plan. Be sure and choose a highly rated company like Blue Cross Blue Shield, Humana, Aetna, or United Healthcare. Also make sure that you choose a plan that has comprehensive major medical coverage to protect you in the case of a large medical bill.
Here is some more information on finding student health insurance.
PSI, international student healthcare
International Health Insurance