Procleix(R) West Nile Virus Assay Confirmed to Have Detected More Than 800 Infected Blood Donations

Procleix(R) West Nile Virus Assay Confirmed to Have Detected More Than 800
Infected Blood Donations
Updated Results From 2003 Mosquito Season Announced During American Association
of Blood Banks Conference 


EMERYVILLE, Calif., Nov. 3  /PRNewswire-FirstCall/ -- Chiron Corporation  today
announced that the Procleix(R) West Nile Virus Assay has identified 861 blood
donations confirmed to be infected with the West Nile virus (WNV) since the
investigational-use-only assay was implemented at the beginning of the 2003
mosquito season.  Since July 1, 2003, more than 80 percent of the blood
donations in the United States have been screened for WNV using the Procleix(R)
System, available in the United States under an FDA-approved Investigational New
Drug (IND) protocol.  Chiron made the announcement during the American
Association of Blood Banks annual meeting in San Diego.

"Blood is needed by someone in our country every two seconds.  By identifying
infected donations, we have potentially saved over a thousand people from
receiving West Nile virus, since most whole blood donations are separated into
multiple components that can be transfused into as many as three different
recipients," said Jim MacPherson, chief executive officer, America's Blood
Centers.  "This should give Americans increased peace of mind about preventing
transmission of the virus through the blood supply."

"Once the West Nile virus emerged as a threat to the blood supply in 2002, the
FDA, manufacturers and the blood bank community worked in unprecedented
collaboration to reduce the risk the virus presented," said Jack Goldstein,
president, Chiron Blood Testing.  "As a result, the Procleix WNV Assay was
available under IND in record time.  Chiron is committed, in cooperation with
its partner Gen-Probe, to continuing to bring new products to market that will
increase the safety of the blood supply, including the Procleix(R) Ultrio(TM)
Assay, which will add a hepatitis B assay to the existing Procleix HIV-1 and
hepatitis C test."

In October 2002, after several cases of WNV transmission were linked to blood
transfusion, the FDA asked manufacturers of blood screening technologies to
create a nucleic acid test (NAT) that could effectively screen donated blood for
WNV.  Chiron, and its collaborator Gen-Probe Incorporated, developed the
Procleix WNV Assay in a record nine months, making it available in time for the
2003 mosquito season.

About Procleix(R) West Nile Virus Assay

The Procleix West Nile Virus (WNV) Assay, a highly sophisticated and sensitive
blood-screening tool developed by Gen-Probe Incorporated and marketed by Chiron
Corporation, demonstrated in pre-clinical testing the ability to detect very low
levels of the virus in blood, even before the body develops antibodies against
the virus.  The Procleix WNV Assay utilizes the same NAT technology and
instrumentation as the already FDA-approved Procleix(R) HIV-1/HCV Assay.

About West Nile Virus

The West Nile Virus causes flu-like symptoms in about 20 percent of those
infected and can cause life-threatening illness in about 1 in 150.  While the
majority of West Nile infections are spread by insects -- primarily mosquitoes
-- scientists confirmed last year that the virus can also be spread through
blood transfusion and organ transplantation.  An average 14 million blood
donations are made annually in the United States, and 4.5 million lives are
saved each year by blood transfusions.

About Chiron

Chiron Corporation, headquartered in Emeryville, California, is a global
pharmaceutical company that leverages a diverse business model to develop and
commercialize high-value products that make a difference in people's lives. The
company has a strategic focus on cancer and infectious disease.  Chiron applies
its advanced understanding of the biology of cancer and infectious disease to
develop products from its platforms in proteins, small molecules and vaccines. 
The company commercializes its products through three business units: 
BioPharmaceuticals, Vaccines and Blood Testing.  For more information about
Chiron, visit the company's website at http://www.chiron.com/.

This news release contains forward-looking statements, including statements
regarding sales growth, product development initiatives, new product marketing,
acquisitions and in- and out-licensing activities that involve risks and
uncertainties and are subject to change. A full discussion of the company's
operations and financial condition, including factors that may affect its
business and future prospects, is contained in documents the company has filed
with the SEC, including the form 10-Q for the quarter ended June 30, 2003, and
the form 10-K for the year ended December 31, 2002, and will be contained in all
subsequent periodic filings made with the SEC. These documents identify
important factors that could cause the company's actual performance to differ
from current expectations, including the outcome of clinical trials, regulatory
review and approvals, manufacturing capabilities, intellectual property
protections and defenses, stock-price and interest-rate volatility, and
marketing effectiveness. In particular, there can be no assurance that Chiron
will increase sales of existing products, successfully develop and receive
approval to market new products, or achieve market acceptance for such new
products. There can be no assurance that Chiron's out-licensing activities will
generate significant revenue, nor that its in-licensing activities will fully
protect it from claims of infringement by third parties. In addition, the
company may engage in business opportunities, the successful completion of which
is subject to certain risks, including shareholder and regulatory approvals and
the integration of operations.

Consistent with SEC Regulation FD, we do not undertake an obligation to update
the forward-looking information we are giving today.

NOTE:  Procleix is a trademark of Chiron Corporation. 

DATASOURCE: Chiron Corporation



CONTACT:  Chiron Corporate Communications& Investor Relations, media,

[phone], or investors, [phone]



Web site:  http://www.chiron.com/ 

Copyright