Origin of viruses which cause hemmoragic fevers?

[chaoseverlasting]

Viruses which cause hemmoragic fevers are usually passed on to humans through animals (eg: Lassa fever, Margburg virus, Ebola, etc). But from where to the animals get the virus from? Where do the viruses originate from? Is there always some animal carrying the virus in an inactive state?

 

[Monique]

Animals can be natural reservoirs for viruses. In many cases, these animals do not become ill when infected. Mosquitos are a common vector that transmits the disease from one animal to the other.

 

[jim mcnamara]

Hantavirus is resident in deer mice populations in the Southwest US. The deer mice become sick, some die from the infection. Not necessarily all.

Humans may pick up the virus from rodent scat and dried urine.. for example, when cleaning out a shed or the garage. The virus remains virulent in the rodent excreta for quite a while as long as it is hidden from direct sunshine and weather.

 

[Chris Hillman]

And to address the original question, possible vectors (in the loosest possible sense) for human illnesses in the news include:

1. in recent years, fruit bats have been implicated as possible vectors for hemorrhagic fevers,

2. civet cats have been implicated as a vector for SARS,

3. horses or perhaps cattle have long been implicated in the evolution of human tuberculosis (recently challenged),

4. deer (or more precisely, deer ticks) appear to be the main vector for Lyme disease,

5. deer rats and other small rodents appear to be a vector for hantavirus,

6. raccoons and bats can transmit rabies to humans,

7. when crows start dying in large numbers, this may indicate that West Nile Virus has arrived in your locale; however, the actual vector for transmission to humans would be a mosquito,

8. there's been some rather speculation that "at any moment" a mutation could result in humans catching a deadly avian flu direcly from sick waterfowl, which should probably treated with more skepticism than hysteria (in particular, don't go off trying to exterminate all those migratory geese).

("Loosest possible sense": I am not being very finicky about distinguishing between "vectors" and "reservoirs".)

I happen to know someone who knows someone who had a relative who was cleaning mouse droppings off shelving in a rural cabin. He contracted hantavirus and died. However, we should stress that this illness is extremely rare in humans. Very few humans are likely to be even be exposed to it.

Google wasn't terribly efficient at finding credible webpages which discuss possible vectors and reservoirs for viral illnesses in humans, but try this: http://web.uct.ac.za/depts/mmi/jmoodie/haemorr.html

 

[majinmonkey]

so where do the animals get it from?

well what are virus's first of all?
Lumps of DNA or RNA encolsed in a protien. Some may have further envelopes but notall so let's disregard that.

Maybe new viruses originate from older virus's misfunctionings. If a virus "takes over" the processes of a damaged or mutated cell, then wouldn't the replicated viruses be subject to whatever problem the cell was having with it's equiptment? Also, i don't think the virus would stop "telling" the cell to copy the genetic material because there is no way for the virus to know of a problem, unless some contain self-diagnostic genes, but I've never heard of that before.

So, it could be due to a mutation, not necesarily bad for the virus however. So do viruses follow the theory of evolution through natural selection? I think its a possibility.