transmitted through blood transfusions or blood products. Improvements in blood donor screening, serologic testing, and transfusion practices have made the U.S. blood supply one of the safest in the world, despite its size and complexity. However, because blood is a human tissue, it is a natural vehicle for transmitting infectious agents. Therefore, continued vigilance is needed to ensure the safety of the U.S. blood supply. • Chronic diseases caused by infectious agents. Several chronic diseases once attributed to lifestyle or environmental factors (e.g., some forms of cancer, heart No data 1979 1982 1985 1988 1991 1994 1997 0 5 10 15 20 25 30 Year Percentage of isolates High Intermediate (≥2 µg/mL) (0.1–1 µg/mL) Sources: 1979–1987 and 1992–1994, CDC Sentinel Surveillance Network; 1995–1997, CDC Active Bacterial Core Surveillance (ABCS) System. FIGURE 1. High and intermediate levels of penicillin resistance in Streptococcus pneumoniae — United States, 1979–1997* *During the 1980s, more than 90% of Streptococcus pneumoniae isolates in the United States were sensitive to penicillin, and high-level resistance to penicillin was not observed. By 1997, however, one in four isolates exhibited some degree of resistance to penicillin; one in seven isolates exhibited high-level resistance. 10 MMWR September 11, 1998 disease, and ulcers) might be caused or intensified by infectious agents (24 ). This new knowledge raises the possibility that certain chronic diseases might someday be treated with antimicrobial drugs or prevented by vaccines. • Vaccine development and use. Certain childhood diseases (e.g., diphtheria, tetanus, polio, measles, mumps, rubella, and Haemophilus influenzae type b disease) have been virtually eliminated in the United States through universal vaccination. However, additional vaccines are needed to prevent diseases that are a societal burden in the United States or internationally (e.g., HIV/AIDS, dengue fever, hepatitis C, and malaria). • Diseases of persons with impaired host defenses. Persons whose normal host defenses against infection have been impaired by illness, by medical treatment, or as a result of age are more likely to become ill with various infectious diseases. Infections that occur with increased frequency or severity in such persons are called opportunistic infections. Health-care providers and scientists must be ready to identify and investigate each new opportunistic infection as it appears, and to learn how to diagnose, treat, control, and prevent it. • Diseases of pregnant women and newborns. Certain asymptomatic infections in a pregnant woman can increase her infant’s risk of prematurity, low birth weight, long-term disability, or death. In addition, infections can be transmitted from mother to child during pregnancy, delivery, or breast-feeding. Effective and accessible prenatal care is essential to the prevention of infection in pregnant women and newborn babies. • Diseases of travelers, immigrants, and refugees. Persons who cross international boundaries (e.g., tourists, workers, immigrants, and refugees) are at increased risk for contracting infectious diseases and can also disseminate diseases to new places. International air travel has increased substantially in recent years, and more travelers are visiting remote locations where they can be exposed to infectious agents that are uncommon in their native countries. ANTICIPATED OUTCOMES Achievement of the objectives described in this plan will improve understanding of infectious diseases and bolster their detection, control, and prevention. The goal of this plan is a stronger, more flexible U.S. public health system that is well prepared to respond to known disease problems and to address the emergence of new infectious pathogens. Implementation of this plan will produce the following results: • A nationwide network for surveillance and response will ensure the prompt identification of emerging infectious diseases. State and local health departments will have the equipment and trained personnel needed to provide the front-line public health response to infectious disease threats. • Intensive population-based surveillance and research programs in at least 10 areas of the United States will generate data to identify new threats to public health and help guide responses to emerging infectious diseases. Vol. 47 / No. RR-15 MMWR 11 • State health departments will rapidly detect and investigate outbreaks of foodborne illnesses by using sophisticated epidemiologic and laboratory techniques. Early detection will facilitate the rapid implementation of control measures and the prevention of illness and death. • Countries in all regions of the world will participate in a global system for surveillance and response that includes surveillance for infectious agents that are resistant to antimicrobial drugs. This effort will be undertaken in partnership with the World Health Organization and other organizations and agencies around the world. • Enhancement of the public health infrastructure will help prepare the United States to respond to bioterrorist incidents. • Improved diagnostic testing methods will be developed for new, reemerging, and drug-resistant pathogens. • A better understanding of risk factors for the development of infection and disease will provide new opportunities for disease