Recent Key Publications Describe Evolving Epidemic of Severe Clostridium difficile-Associated Disease

'The New England Journal of Medicine' Describes Worsening Epidemic; 'Morbidity and Mortality Weekly' Highlights Spread into Community

Exton, Pennsylvania, UNITED STATES

EXTON, Pa., Dec. 8, 2005 (PRIMEZONE) -- ViroPharma Incorporated (Nasdaq:VPHM) today announced that The New England Journal of Medicine (NEJM) and the Center for Disease Control and Prevention's (CDC) Morbidity and Mortality Weekly (MMWR) have further described the ongoing epidemic of severe disease caused by Clostridium difficile, including additional characterization of the variant strain that is causing significant increases in the rates of morbidity and mortality in 16 states across the U.S. and in Canada, and the spread of this once hospital based disease into community settings.

ViroPharma is engaged in efforts to raise awareness of this growing problem through the launch of a major educational campaign on C. difficile-associated disease (CDAD). The company commercializes Vancocin(r), which is indicated for the treatment of antibiotic-associated pseudomembranous colitis caused by C. difficile.

"The epidemiology of CDAD is changing dramatically," commented Steven Gelone, PharmD., ViroPharma's director of medical affairs. "The presence of severe CDAD in patients previously thought to be at low risk of acquiring disease is of great concern. Additionally, it appears that the epidemic strain is associated with an increased incidence of disease in the hospital, as well as greater morbidity and mortality. This strain has displayed decreased in vitro susceptibility to fluoroquinolone antibiotics, and exposure to these drugs has been identified as a risk factor for disease. This significantly complicates efforts directed at controlling the spread of CDAD."

Data on characteristics of the epidemic strain and the subsequent morbidity and mortality associated with C. difficile disease were published in the December 8, 2005 edition of The New England Journal of Medicine (Vol. 353, No. 23, 2433-2449 and 2503-2505). In an accompanying editorial, John G. Bartlett, M.D. and Trish M. Perl, M.D. noted that the data presented in this week's edition of the journal from studies is the U.S. and Quebec support the concept that a more virulent strain of C. difficile is causing epidemic disease at selected locations, with a wider distribution than previously identified in the medical literature. They suggest that control hinges on prevention of spread, early recognition of cases, and optimal management of disease.

As described in the NEJM paper entitled "An Epidemic, Toxin Gene-Variant Strain of Clostridium difficile" (L. Clifford McDonald, M.D. et al.), a total of 187 C. difficile isolates from health care facilities in six U.S. states were characterized in an effort to describe the new strain which is causing increased virulence and resistance to common fluoroquinolone antibiotics. According the publication, results of the characterization studies showed that all BI isolates, historical (pre-2001) and recent (since 2001), were of toxinotype III, were positive for binary toxin, and contained a deletion to the toxin repressor gene tcdC. This deletion may be associated with significantly increased production of Toxin A and B, which may cause more severe disease. All BI isolates, recent and historical, had similar rates of resistance (79 percent) to clindamycin. However, resistance to newer and commonly used fluoroquinolones, gatifloxican and moxifloxican, was only associated with newer strains, and not seen in any of the historic strains. The authors concluded that this BI strain "has become more resistant to fluoroquinolones, and has emerged as a cause of geographically dispersed C. difficile-associated disease."

Similarly, data from "A Predominantly Clonal Multi Institutional Outbreak of Clostridium difficile-Associated Diarrhea with High Morbidity and Mortality" (Vivian G. Loo, M.D. et al.) further described the epidemic strain in Quebec. A total of 1703 patients with nosocomial CDAD from 12 Quebec hospitals were identified. Isolates from a subgroup of these patients were typed and analyzed for binary toxin genes and partial deletions of tcdC. According the publication, results of this prospective study showed that incidence of disease had risen dramatically to 22.5 per 1000 admissions, with a 30-day attributable mortality rate of 6.9 percent The authors concluded that this strain of C. difficile was responsible for the described outbreak of CDAD in Quebec, and that exposure to fluoroquinolones or cephalosporins was a risk factor. The study noted that transmission of this predominant strain among hospitals "could have resulted from transfers of colonized or infected patients or perhaps from colonized healthcare workers who worked in multiple institutions."

In addition, the December 2, 2005 Morbidity and Mortality Weekly (MMWR) (Vol. 54, No. 47, 1201-1205) included a report describing the presence of severe CDAD in otherwise healthy people living in the community, and other populations previously thought to be at low risk. The report entitled "Severe Clostridium difficile-Associated disease in Populations Previously at Low Risk - Four States, 2005" described results of recent investigations in Pennsylvania and other states which indicated the presence of severe CDAD, including disease related fatalities, in out-patient populations generally considered to be at low risk of CDAD. Ten peripartum and 23 community acquired cases many with minimal or no exposure to a health care setting, were reported from four states during May and June of 2005. Overall, 73 percent of these cases were associated with antimicrobial use within three months before diarrhea onset. Thirty percent of these cases required hospitalization to treat their CDAD; 15 percent necessitated a visit to the emergency department. According to the report, these data "underscore the importance of judicious antimicrobial use, the need for community clinicians to maintain a higher index of suspicion for CDAD, and the need for surveillance to better understand the changing epidemiology of CDAD."

C. difficile is a bacterium, which under certain circumstances, typically after antibiotic therapy, can colonize the lower gastrointestinal tract where it may produce toxins which cause inflammation of the colon and diarrhea, and the associated complications of disease. Advanced age, gastrointestinal surgery/manipulation, long length of stay in healthcare settings, a serious underlying illness and immunocompromising conditions are associated with increased risk of disease. According to the CDC, there are approximately 3,000,000 cases of antibiotic associated diarrhea per year, of which 15 to 25 percent are caused by C. difficile.

About ViroPharma Incorporated

ViroPharma Incorporated is a biopharmaceutical company dedicated to the development and commercialization of products that address serious diseases treated by physician specialists and in hospital settings. ViroPharma commercializes Vancocin(r), approved for oral administration for treatment of antibiotic-associated pseudomembranous colitis caused by Clostridium difficile and enterocolitis caused by Staphylococcus aureus, including methicillin-resistant strains (for prescribing information, please download the package insert at ViroPharma currently focuses its drug development activities in viral diseases including cytomegalovirus (CMV) and hepatitis C (HCV). For more information on ViroPharma, visit the company's website at

Certain statements in this press release may contain forward-looking statements that involve a number of risks and uncertainties, including those relating to continued increase in C. difficile disease incidence and severity. Our actual results could differ materially from those results expressed in, or implied by, these forward-looking statements. The commercialization of pharmaceutical products is subject to risks and uncertainties. There can be no assurance that there will be no decreases in the rate of infections for which Vancocin is prescribed or that the prescribing or procedural practices of infectious disease, gastroenterologists and internal medicine doctors will not change in a manner adverse to us. These factors, and other factors, including, but not limited to those described in ViroPharma's current report on Form 8-K filed with the Securities and Exchange Commission on November 29, 2005, could cause future results to differ materially from the expectations expressed in this press release. The forward-looking statements contained in this press release may become outdated over time. ViroPharma does not assume any responsibility for updating any forward-looking statements.


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