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Below are two quotes from the CDC about Hantavirus:

"Researchers believe that people may be able to get the virus if they touch something that has been contaminated with rodent urine, droppings, or saliva, and then touch their nose or mouth."

and:

"You cannot get the virus from touching or kissing a person who has HPS."

This is hard to believe. So, since human saliva is not a problem, can you be contaminated by human urine or human droppings? The only way for me to interpret this logically is to say that this virus lives at the end of the digestive tract (for both rodents and humans) and people can be kissed because they have much better hygiene than rodents. Is there a better interpretation?

Also, is there a simple reason why Hantavirus leaves the mouth (moving to the end of the digestive tract) of an infected animal, but influenza does not?

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I think (after research) that we don't know enough. As to a possible explanation of the different behaviour in rodents vs influenza, rodents don't get ill from Hanta, so the immune system isn't involved. –  rwst Sep 2 '12 at 13:47
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2 Answers 2

Viruses can have many different conditions necessary for transmission. Viruses which have membrane surface coats (like HIV ) need to be in water all the time to survive. Cold and flu viruses are more resilient and can survive on a surface such as a doorknob with a halflife of 18 hours(!). Fortunately we are also have a reasonable intrinsic resistance to cold and flu and I think most infections do not result in symptoms.

Viruses often only infect some parts of the body. Venerial diseases are a classic example of this where only contact of genitalia might cause transmission. Its probable that Hantavirus is not excreted through the sweat glands or in saliva. If it did it would certainly be a more devastating disease. It may also only be serious when the virus is introduced into the lungs, which may make transmission difficult.

For Hantavirus human to human transmission looks possible as observed by these folks. Even so, transmission is still so rare that there is no accounting for it in public health policy. (they might also have been mistaken!). Its possible that the virus requires transmission from a mouse to be virulent in humans. Its possible that the human transmission mechanism is so improbable (ingestion of faeces of infected human for instance) that you just dont' see it happening with the few cases of Hantavirus infection we have on the books.

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Thanks. I understand much is not known, but in your expert opinion/guess, do you think the probability of catching Hantavirus from kissing an infected rodent is significantly higher than that from kissing an infected human? If so, is it just because of the hygiene point in my question (i.e., the probability would be the same if the rodent's mouth only touched clean food after it got infected)? I'm struggling with understanding why rodents are so different from humans; rwst's point about rodents not getting sick could be a factor here. –  bobuhito Sep 18 '12 at 22:37
    
Probably somewhat higher, but the virus seems to come from the other end of the rodent. It might not be a respiratory virus in mice at all. –  shigeta Sep 18 '12 at 22:44
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This paper is referred to in the Wikipedia entry for hantavirus as an example of human-human transmission. It may discuss the reasons why transmission is not normally via this route.

Martinez VP et al. (2005) Person-to-person transmission of Andes virus. Emerg Infect Dis. 11:1848-53

Despite the fact that rodents are considered to be the infectious source of hantavirus for humans, another route of transmission was demonstrated. Andes virus (ANDV) has been responsible for most of the cases recorded in Argentina. Person-to-person transmission of ANDV Sout lineage was described during an outbreak of hantavirus pulmonary syndrome in southwest Argentina. In this study, we analyzed 4 clusters that occurred in 2 disease-endemic areas for different ANDV lineages. We found new evidence of interhuman transmission for ANDV Sout lineage and described the first event in which another lineage, ANDV Cent BsAs, was implicated in this mechanism of transmission. On the basis of epidemiologic and genetic data, we concluded that person-to-person spread of the virus likely took place during the prodromal phase or shortly after it ended, since close and prolonged contact occurred in the events analyzed here, and the incubation period was 15-24 days.

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Wow, maybe you could've translated that to normal-human-understandable language :) –  Steven Roose Sep 3 '12 at 9:15
    
That paper doesn't help answer my two specific questions,and makes me worry that any Hantavirus might be person-to-person transmittable (maybe only in the prodromal phase). I wonder what the CDC's confidence level needs to be to print something... –  bobuhito Sep 7 '12 at 2:23
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