[Table of Contents]

Volume: 23S1 - January 1997

Canadian Contingency Plan for Viral Hemorrhagic Fevers and Other Related Diseases

THE RISK TO CANADA

The speed and volume of international travel and commerce have increased the risk that persons incubating any disease - including unusual or emerging communicable diseases - may arrive in Canada. Given the ease of modern air travel and the integration of international and domestic routes, passengers may arrive at many destinations in Canada shortly after leaving isolated or distant origins. Consequently, the presentation of one of these infections may occur in regions of the country where immediate access to specialist consultation may be difficult.

Appropriate control measures for situations involving these diseases are based both on an appreciation of the true risks associated with these communicable diseases as well as on a widespread understanding of the protocols in place to manage their occurrence, even if these events are rare or unlikely.

Unusual or emerging VHFs may be caused by members of the following virus groups:

• the Arenavirus group, including Lassa, Junin, Sabia and Machupo viruses^(8,9)
• the Bunyavirus group, including Crimean-Congo hemorrhagic fever virus, and Rift Valley fever virus^(10,11)
• the Filovirus group, including Marburg virus and Ebola virus^(12-14) , and
• the Flavivirus group including Yellow fever virus⁽¹⁵⁾ .

(The identification and classification of viral pathogens is a continuous process. The above noted listing indicates representative examples and is not meant to be definitive.)

As noted above, other imported communicable diseases of high infectivity and significant morbidity or mortality may require a coordinated national response in a manner similar to the unusual or emerging communicable viral diseases.

While many of VHFs were initially considered to be highly communicable between humans, this concept has not been substantiated. Although nosocomial transmission has occurred in areas with endemic disease, accumulated evidence shows that transmission of these viruses does not commonly occur through casual or remote contact^(16-18) . Several importations to non-endemic countries have occurred without subsequent disease outbreaks. Indeed, with the exception of Marburg VHF, no secondary cases have been identified during importation episodes^(4,6,10) .

Body secretions and excretions, blood, semen, and tissue specimens from infected patients contain the virus. Evidence is accumulating to suggest that the risk of infection increases with the clinical progression of the disease. Persons at highest risk of secondary infection are those who are in closest contact with an infected person or his/her body fluids during the period of incubation and acute illness. Such persons include those with prolonged or close (face-to-face or exposure to secretions) contact with patients, those providing direct medical and nursing care, and laboratory workers handling the patient's specimens⁽⁷⁾ . Data evaluating transmission by the respiratory route are scarce, but the possibility remains that such transmission may rarely occur with several of these or other viral agents.

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