taken together the viruses that cause viral hemorrhagic fevers are distributed over much of the globe. however because each virus is associated with one or more particular host species the virus and the disease it causes are usually seen only where the host species live(s). some hosts such as the rodent species carrying several of the new world arenaviruses live in geographically restricted areas. therefore the risk of getting vhfs caused by these viruses is restricted to those areas. other hosts range over continents such as the rodents that carry viruses which cause various forms of hantavirus pulmonary syndrome in north and south america or the different set of rodents that carry viruses which cause hemorrhagic fever with renal syndrome in europe and asia. a few hosts are distributed nearly worldwide such as the common rat. it can carry seoul virus a cause of hfrs; therefore humans can get hfrs anywhere where the common rat is found. while people usually become infected only in areas where the host lives occasionally people become infected by a host that has been exported from its native habitat. for example the first outbreaks of marburg hemorrhagic fever in marburg and frankfurt germany and in yugoslavia occurred when laboratory workers handled imported monkeys infected with marburg virus. occasionally a person becomes infected in an area where the virus occurs naturally and then travels elsewhere. if the virus is a type that can be transmitted further by person-to-person contact the traveler could infect other people. because more and more people travel each year outbreaks of these diseases are becoming an increasing threat in places where they rarely if ever have been seen before.
where are cases of viral hemorrhagic fever found?