Mode of Transmission


Ebola hemorrhagic fever

Spread from person with acute infection by contact with blood, secretions, or other material.

Repeated outbreaks with high mortality in sub-Saharan Africa; secondary spread of infection has occurred in health care settings and in households in Africa; reservoir for the virus not yet identified.

Enterovirus 71

Direct contact with material from infected persons (nose/ throat discharge or droplets, feces).

Multiple outbreaks documented since 1974; major epidemic in Taiwan, 1998, with highest incidence in children <1 year, and again in 2000; virus highly mutable.

Hantavirus pulmonary syndrome

(Sin Nombre and multiple other hantaviruses)

Presumed aerosol transmission of excreta from infected rodents.

Zoonosis; rodent reservoir host; sporadic cases and outbreaks especially in North and South America; rise in reported human cases linked to factors that lead to expansion of rodent population (e.g., rainfall, weather conditions), increased human–rodent contact (changes in land use), and increased recognition.

Hendra virus

(related to Nipah virus)

Humans infected by direct contact with infected horses.

Zoonosis; 3 human cases in Australia in 1994–1995; fruit bats may be reservoir host.


Person to person via blood and body fluids.

Continued spread and rising rates of infection in some areas; emergence of resistant strains related to antiviral therapy; resistant strains can be transmitted; infected persons can be infected with second strain; HIV-associated immunosuppression contributes to increase in multiple other infections, including TB.

Influenza, avian H5N1

Presumed direct spread from chickens or other birds to humans.

Major epizootics of influenza H5N1 in avian species in Hong Kong in 1997 and spread of avian virus to humans; millions of chickens killed to halt spread of infection to humans; virus infected multiple avian species; no or limited spread of H5N1 from human to human.

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