Infectious Disease Therapies Research and Innovation Act of 2020 This bill exempts from the definition of passive activity , for purposes of the passive loss tax rules, any qualified medical research activity of a specified medical research small business pass-thru entity. The bill defines specified medical research small business pass-thru entity as any domestic pass-thru entity if more than 80% of such entity's expenditures on research are paid or incurred in connection with qualified medical research activities and the gross receipts of such entity for the taxable year are less than $1 million.