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                                                                    EXHIBIT 23.1
 
               CONSENT OF ERNST & YOUNG LLP, INDEPENDENT AUDITORS
 
   
We consent to the reference to our firm under the caption "Experts" in Amendment
No. 1 to the Registration Statement (Form S-3 No. 333-72185) and related
Prospectus of Cerus Corporation for the registration of shares of its common
stock and to the incorporation by reference therein of our report dated January
27, 1998, except for Note 2 as to which the date is March 6, 1998 with respect
to the financial statements of Cerus Corporation included in its Annual Report
(Form 10-K) for the year ended December 31, 1997 filed with the Securities and
Exchange Commission, and to the use of our report dated January 22, 1999, except
for Note 2 as to which the date is January 30, 1999 and Note 5, as to which the
date is March 3, 1999, with respect to the financial statements of Cerus
Corporation included herein.
    
 
   
                                                           /s/ ERNST & YOUNG LLP
    
 
Walnut Creek, California
   
March 8, 1999