In order that the threats posed by emerging viruses and other agents can be dealt with effectively, it is important that world-wide surveillance systems are in place. There need to be effective systems that warn when agents such as the SARS coronavirus emerge.
The scheme for monitoring influenza virus strains provides a good model for a surveillance system. In this scheme, which is co-ordinated by the United Nations World Health Organisation (WHO), isolates of influenza virus from laboratories around the world are sent to Collaborating Centres for Influenza Reference and Research in London, Atlanta, Melbourne and Tokyo. Antigenic variation of the virus in humans and in animals (especially birds and pigs) is monitored, and twice a year the WHO recommends the virus strains to be mass-produced for incorporation into influenza vaccines.
There was some delay in alerting the world to SARS but, once it was apparent that this virus posed a major threat, work got under way in a number of virology laboratories. The virus was isolated in February 2003 and three months later its genome had been sequenced. The following year a paper was published reporting compounds that inhibit replication of the virus, while other papers reported the cell receptor of the virus and the structure of its replicase protein.
Diagnostic laboratory methods to detect evidence of SARS coronavirus in samples from patients rapidly became available; tests based on immunofluorescence and RT-PCR were developed. The health of international travellers was monitored (Figure 21.12) and those found to be infected with the virus were nursed in isolation. These measures brought the SARS outbreak under control.
When there is an outbreak of a highly infectious virus, such as the SARS coronavirus or Ebola virus, infected patients and their contacts are quarantined. Control measures for some outbreaks include slaughter of animals that are infected and those that have been in contact with infected animals. This has been a key measure in dealing with outbreaks of foot and mouth disease (cattle and sheep), Nipah virus (pigs) and avian influenza (poultry).
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