Explains the new methodologies by which viral diseases can be definitively diagnosed in a few hours, especially molecular methods. The many new methods now being developed are based largely on the application of the polymerase chain reaction to the detection of viral genomic material. Accessible to

Virus Variability and Impact on Epidemiology and Control of Diseases E. Kurstak and A. Hossain I. INTRODUCTION An important number of virus infections and their epidemic developments demonstrate that ineffec tiveness of prevention measures is often due to the mutation rate and variability of viruses (Kurstak et al., 1984, 1987). The new human immunodeficiency retroviruses and old influenza viruses are only one among several examples of virus variation that prevent, or make very difficult. the production of reliable vaccines. It could be stated that the most important factor limiting the effectiveness of vaccines against virus infections is apparently virus variation. Not much is, how ever, known about the factors influencing and responsible for the dramatically diverse patterns of virus variability. II. MUTATION RATE AND VARIABILITY OF HUMAN AND ANIMAL VIRUSES Mutation is undoubtedly the primary source of variation, and several reports in the literature suggest that extreme variability of some viruses may be a consequence of an unusually high mutation rate (Holland et al., 1982; Domingo et al., 1985; Smith and Inglis, 1987). The mutation rate of a virus is defined as the probability that during a single replication of the virus genome a particular nucleotide position is altered through substitution, deletion, insertion. or recombination. Different techniques have been utilized to measure virus mutation rates, and these have been noted in the extent of application to different viruses."

Viral Vaccines Joseph L. Melnick As with history in general, the history of vaccines needs to be reexamined and updated. My task is to look back to see what has been successful and to look forward to see what remains to be accomplished in the prevention of viral diseases by vaccines. Also, I shall refer to the pertinent material discussed at two recent conferences of the Institute of Medicine, National Academy of Sciences, on virus vaccines under development and their target populations in the United States (1985b) and in developing countries (1986). These reports, plus a third on Vaccine Supply and Innovation (1985a), should be required reading for all those in both the public and the private sector who have a responsibility or interest in vaccines for the prevention of human disease. It has been through the development and use of vaccines that many viral diseases have been brought under control. The vaccines consist either of infectious living attenu ated viruses or of noninfectious killed viruses or subviral antigens. When we look at the record, it is the live vaccines that have given the great successes in controlling diseases around the world. Examples are smallpox, yellow fever, poliomyelitis, measles, mumps, and rubella."

Viral Vaccines Joseph L. Melnick As with history in general, the history of vaccines needs to be reexamined and updated. My task is to look back to see what has been successful and to look forward to see what remains to be accomplished in the prevention of viral diseases by vaccines. Also, I shall refer to the pertinent material discussed at two recent conferences of the Institute of Medicine, National Academy of Sciences, on virus vaccines under development and their target populations in the United States (1985b) and in developing countries (1986). These reports, plus a third on Vaccine Supply and Innovation (1985a), should be required reading for all those in both the public and the private sector who have a responsibility or interest in vaccines for the prevention of human disease. It has been through the development and use of vaccines that many viral diseases have been brought under control. The vaccines consist either of infectious living attenu ated viruses or of noninfectious killed viruses or subviral antigens. When we look at the record, it is the live vaccines that have given the great successes in controlling diseases around the world. Examples are smallpox, yellow fever, poliomyelitis, measles, mumps, and rubella."

Virus Variability and Impact on Epidemiology and Control of Diseases E. Kurstak and A. Hossain I. INTRODUCTION An important number of virus infections and their epidemic developments demonstrate that ineffec tiveness of prevention measures is often due to the mutation rate and variability of viruses (Kurstak et al., 1984, 1987). The new human immunodeficiency retroviruses and old influenza viruses are only one among several examples of virus variation that prevent, or make very difficult. the production of reliable vaccines. It could be stated that the most important factor limiting the effectiveness of vaccines against virus infections is apparently virus variation. Not much is, how ever, known about the factors influencing and responsible for the dramatically diverse patterns of virus variability. II. MUTATION RATE AND VARIABILITY OF HUMAN AND ANIMAL VIRUSES Mutation is undoubtedly the primary source of variation, and several reports in the literature suggest that extreme variability of some viruses may be a consequence of an unusually high mutation rate (Holland et al., 1982; Domingo et al., 1985; Smith and Inglis, 1987). The mutation rate of a virus is defined as the probability that during a single replication of the virus genome a particular nucleotide position is altered through substitution, deletion, insertion. or recombination. Different techniques have been utilized to measure virus mutation rates, and these have been noted in the extent of application to different viruses."

Volume 3 is devoted to the latest diagnostic technology for virus diseases, particularly molecular methodologies.