Jane Leese, M.D.
Senior Medical Officer, Immunization Team Department of Health, London
The Institute of Medicine (1992) defined emerging and reemerging infectious diseases as those “diseases of infectious origin whose incidence in humans has increased within the past two decades, or threatens to increase in the near future.” This definition is wide, encompassing not only new entities, but also new incidents or outbreaks of established diseases with public health implications, changing trends, and diseases that have increased in importance because of, for example, the actual or potential emergence of antimicrobial resistance.
Diseases appear on the national or international political agenda for a variety of reasons: (1) new scientific evaluations clearly demonstrate a risk or potential risk to public health (this may not, however, be enough on its own); (2) a sudden, rather than an insidious, onset of an infectious disease; (3) preconceived perceptions of a disease (e.g., the outbreak of plague in India in 1994 was associated with international hysteria out of proportion to the risk on the basis of preconceived notions of the Black Death and other historical incidents); (4) a risk to trade or tourism; (5) extensive media coverage; (6) powerful lobbies at work; or (7) the issuance of an authoritative report from a respected body. A variety of reasons then affect how long a disease stays on the agenda, many of which are not necessarily scientifically or clinically appropriate. Another influence is cost. For example, in the United Kingdom a report from the National Audit Office on the cost to the National Health Service of hospital-acquired infections is likely to focus action on such infections as a developing priority.
The study of influenza has provided useful experience in planning for an emerging infectious disease. In the United Kingdom it has been estimated that some 3,000 to 4,000 people die from influenza every year. In 1989, the most severe of recent epidemics, it was estimated that 26,000 people died from an influenza-related illness during the 6 to 8 weeks of the epidemic. Drawing on the experience and on experiences with previous pandemics of the last century, the United Kingdom has developed a national pandemic influenza contingency plan. The plan defines the roles and responsibilities of all the organizations and people who would be involved in the response to a new pandemic. What first emerges from this exercise is the large number of people who would be involved in the response and therefore the need for strong coordination.
The plan moves in phases, from the interpandemic period, through recognition of a new strain with pandemic potential, to outbreaks of illness outside the United Kingdom, outbreaks within the United Kingdom, the pandemic stage