1998 Richard J. Duma/NFID Annual Press Conference and Symposium on Infectious Diseases
Please Choose a Presenter
» Nancy J. Cox, M.D.: "Avian Influenza: What's Next?"
» William R. Jarvis, M.D.: "Vancomycin-Resistant Staphylococcus Aureus: The New Scourge?"
» Michael T. Osterholm, Ph.D., M.P.H.: "Bioterrorism: Are We Prepared?"
» Bruce G. Weniger, M.D.: "Creative ways to Vaccinate: Can We Throw away the Needle and Syringe?"
Avian Influenza: What's Next?
By Nancy J. Cox, M.D.
Eighteen cases of human influenza caused by influenza A(H5N1) viruses that were previously believed only to infect birds occurred in Hong Kong during 1997. An international investigation was mounted to examine the epidemiology and virology of this unique situation. This report will include a summary of the studies undertaken during the Hong Kong investigation along with key results. The emergence of the influenza A(H5N1) viruses in humans was an alarm bell for the entire world; we must remain vigilant because the next influenza pandemic could strike at any time, even if influenza A(H5N1) viruses are contained.
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Vancomycin-Resistant Staphylococcus Aureus: The New Scourge?
William R. Jarvis, M.D.
During the past decade, antimicrobial resistance has become a major public health problem in the United States and throughout the world. In the 1980s, methicillin-resistant Staphylococcus aureus (MRSA) first emerged and then became endemic in many U.S. hospitals. This resulted in the widespread use of vancomycin-the only antimicrobial agent then uniformly effective for the treatment of serious MRSA infections. Then, in late 1989 and the early 1990s, vancomycin-resistant enterococcus (VRE) emerged and became endemic in many U.S. hospitals. In vitro studies showed that the genetic material coding for vancomycin resistance, called vanA, vanB and vanC genes, could be transferred from VRE to S. aureus producing a strain of S. aureus resistant to vancomycin. This led to increasing concern that vancomycin- or glycopeptide-resistant S. aureus would emerge-an organism which, if it were resistant to other commonly used agents, would be virtually untreatable. To decrease the risk of such resistance developing, the Centers for Disease Control and Prevention (CDC) published recommendations for the prevention of transmission of vancomycin resistance; these recommendations highlighted the appropriate uses for vancomycin.
In May 1996, the first strain of S. aureus with reduced susceptibility to vancomycin (glycopeptide-intermediate resistant S. aureus [GISA]) in the world was identified in Japan. The strain caused a surgical site infection in a pediatric patient after cardiac surgery. It appeared that a previous MRSA strain had developed decreased susceptibility to vancomycin. Fortunately, the GISA strain was susceptible to an aminoglycoside and ampicillin/sulbactam. The infection was successfully treated with combined surgical and antimicrobial therapy.
The above infection was reported in the CDC's Morbidity and Mortality Weekly Report in July 1997. In August 1997, two patients infected with MRSA strains with reduced susceptibility to vancomycin were reported from Michigan and New Jersey. Both these patients had serious infections, i.e., peritonitis or bloodstream infections. In both patients, the respective MRSA strains had acquired decreased susceptibility to vancomycin following prolonged exposure to vancomycin. Fortunately, the GISA strains from each of these patients was susceptible to alternative antimicrobial agents. One patient was successfully treated, but the second patient died of a superinfection. Epidemiologic investigations documented that the patients had been placed in isolation during hospitalization, and the transmission of the GISA strains to either patients, healthcare workers or family members had not occurred.
Numerous steps are being taken to reduce the risk of further emergence of GISA. These include the publication of CDC recommendations for the appropriate use of vancomycin and for isolation precautions for patients colonized or infected with GISA strains, education of laboratory personnel about the best methods to identify these strains (some automated antimicrobial susceptibility methods work better than the disk diffusion method) and enhancement of national and international surveillance systems to detect GISA strains which emerge. Keys to the prevention of the further emergence and spread of GISA will be more judicious use of vancomycin, enhanced laboratory methods to identify GISA, active surveillance for GISA infections and complete implementation of recommended infection control measures should GISA-infected or colonized patients be identified
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Bioterrorism: Are We Prepared?
By Michael T. Osterholm, Ph.D., M.P.H.
The use of biological agents-bacteria, viruses or toxins-as weapons of mass destruction have historically been considered in the context of war and military populations. However, recent events support the conclusion that rogue nations and extremist groups worldwide are increasingly learning how to manufacture biological agents and develop delivery systems for their dissemination in civilian populations. Thus, the likelihood that a biological terrorism attack will occur in the United States in the near future continues to grow.
Diseases such as anthrax, smallpox, plague, botulism and viral hemorrhagic fevers are the most likely candidates for biological terrorism. Agents responsible for these diseases have a number of characteristics which make them ideal for potential biological terrorism use. They are inexpensive and easy to produce, easily aerosolized, able to survive sunlight and heat and are capable of causing lethal or disabling disease. In addition, for the diseases of smallpox and plague, person-to-person transmission is an important consideration. Finally, effective therapy or prophylaxis is limited for each of these diseases.
Unlike chemical or explosive devices which typically cause immediate trauma or disease, these biological agents have incubation periods of days. For this reason, it is the physician or other emergency room personnel who will be the first line of defense when such a disaster occurs. Only through timely and comprehensive public health surveillance will the nature of a terrorist event become evident. Yet, as a nation our federal, state and local infrastructure remains largely unprepared to deal with this likely disaster.
A biological terrorism event will be difficult to detect when patients with vague symptoms seek medical care. Only when patients present in number and require intensive care will we recognize the event. The health care system of any community, regardless of size, will be overwhelmed. Special medications or vaccines not generally available in standard pharmaceutical stocks potentially will be required. For example, today we have inadequate supplies of smallpox and anthrax vaccines for civilian use, and there are no current efforts to improve upon this situation. Health care professionals and laboratory personnel may need added physical protection. The psychological impact on the population, including health care workers, will be substantial.
The current federal, state and local response to bioterrorism largely relies on the well-established HAZMAT approach to disaster management. However, this framework for response will be of little use for such an event. The general framework for a federal government response to terrorist incidents is provided by Presidential Directive 39 (PDD-39), United States Policy on Counterterrorism, signed by President Clinton in 1995. While this directive does not provide a detailed concept of operations, it defines broad responsibilities and coordination relationships among responsible federal agencies. To date, the agency coordination and plans for federal preparedness are seriously lacking.
This presentation will outline the reasons for serious concern for biological terrorism today, including the health impact on civilians, populations and the groups or individuals likely to be responsible for such an event; the possible agents and mechanisms of deployment; the implications for the health care and public health systems and the lack of preparedness in the United States.
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Creative ways to Vaccinate: Can We Throw away the Needle and Syringe?
By Bruce G. Weniger, M.D.
The biotechnology revolution is producing a growing bounty of new vaccines. Since 1980, four diseases have become newly vaccine-preventable in the United States, and several other diseases will finally fall prey to immunization in the next few years. These are wonderful fruits of new technologies, but vaccines requiring injection with needle and syringe pose daunting challenges for health care providers to incorporate them into immunization programs to prevent disease and improve the health of society.
As recently as 1989, the recommended national immunization schedule in the United States required a total of eight injections of vaccine for children from birth through 16 years of age. The minimum number now required is 14 injections. Up to four injections may be required at a single visit in the second year of life for vaccines due at that age. Many providers and parents, however, are reluctant to administer so many injections during a single visit because of the childĖs fear of needles and pain. This results in deferred vaccination, additional time and cost for followup visits and potential disease if followup is delayed or missed. Needles and syringes have additional drawbacks such as unsterile reuse in developing countries, improper disposal and needlestick injuries.
A short-term solution for increasing numbers of vaccines is to combine those for several diseases into the same syringe, which has been done successfully for many existing products. But combination vaccines require much time and effort to overcome potential problems of chemical incompatibility and immunologic interference. Combining monopoly vaccines with others may also exacerbate a trend toward decreased competition and consolidation in the vaccine industry.
A medium-term solution to needle phobia is to eliminate the needle: Drugs can be administered by jet injectors which shoot a fine stream of liquid under high pressure through a small orifice in the skin. Although not yet a painfree process, ongoing work to develop a new generation of such needle-free devices may use smaller volumes to reduce the pain or deliver separate vaccines in parallel injections in a single painful event.
Long-term solutions may involve vaccines given by mouth or by aerosol into the nose. Indeed, the new rotavirus vaccine expected to be licensed shortly to prevent diarrhea in infants will be administered by drops, like the Sabin oral polio vaccine. An influenza vaccine sprayed into the nose appears promising and may replace influenza vaccines now given by injection. Experimental oral cholera and salmonella vaccines might permit a variety of other diseases to be prevented by genetic engineering of these vaccines. Vaccination through skin might also become painfree: Experimental DNA vaccines are now delivered relatively painlessly by blowing them into the skin. Mice have been immunized by simply dropping liquid vaccines onto bare skin. Vaccines produced in plants hold hope for inexpensive mass production and immunization by ingestion. Encapsulation technologies to shield vaccines from the harsh acid environment of the stomach may permit vaccines now delivered by injection to be used orally. New vaccines are very expensive to develop, but those which do not require administration by needle and syringe may represent innovations well worth paying for.
