Emerging virus diseases: can we ever expect the unexpected?

Figures & data

Figure 1 Disease emergence pathways and responses to zoonotic infections.

Table 1 The key stages in virus emergence

Stage	Feature	Outcome
I	Constant exposure to infected animals	No human disease
II	Occasional exposure due to change in emergence factors	Occasional human infections
III	Occasional exposure due to change in emergence factors	Continuing animal reservoir but human infection and transmission
IV	No exposure to infected animals	Human to human transmission only

Figure 2 SIV strains and cross-species transmission to great apes and humans. Old World monkeys are naturally infected with over 40 different strains of SIV. These strains are species-specific and hence are denoted with a suffix to indicate their species of origin. Known cross-species transmission events to great apes and humans are highlighted in red.

Table 2 The major criteria for recognition and reaction to emerging infections

• Alerting clinicians to expect and react to any unusual clinical presentation

• Swiftness of response

• Provision of a high standard of diagnostic capabilities plus availability of reference reagents

• Availability of containment facilities to at least level 3

• Involvement of epidemiologists and communicable disease specialist at the earliest opportunity

• A capacity to react with appropriate control and prevention measures