Explain: why you CAN catch e-coli from a dog, but you can't catch the flu from a dog?

Question

My guess is, the flu comes from a virus, and viruses are very similar to their host. So viruses that attack dogs have DNA fractions very similar to theirs but not to ours so we can't catch their flu. E-coli which is a bacteria, doesn't have to be similar to it's host, which is why we can catch it from virtually anything. Right???

Answer 1

well,   you are part right on the viruses,    they are more "similar/adapted" to their host as oppose to the bacteria in this case.   It is not that DNA fractions of the virus are more similar,  but instead it is the way in which a virus binds to a cell and causes the engulfment/uptake of that virus. all of our cells have specific proteins which are embedded into the cell membrane and take part in all sorts of opperations.   Some serve as receptors for cellular cues and signals,  some help bind with other cells to create tissues, and some just bind to extracellular matrix, to name a few.    In this case viruses have adapted to bind to host cells by  attaching to one of these transmembrane proteins.   If you the host happen to have these proteins which viruses bind to then you are succeptible to their infection.  

In the case of the flu,  dogs do not have the same "receptors" for the serotype of virus and thus cannot be transfered to humans and vice versa (unlike the ferret and human).    As for E-coli,      humans and animals for the most part have similar digestive tracts  and thus have similar bacteria living within all of us, although humans have been out of the wild for some time so we have lost some of our normal flora/bacteria.  Thus we may be prone to infection from e-coli from other species because bacteria only need to be occupying an area in order to cause an infection as oppose to being taken up and having its DNA be incorporated into our own.

Answer 2

Because the flu that dogs get is actually a different virus from what humans get.

But it is entirely possible that overtime, the flu would develop to affect both dogs AND humans. See, when the doggy flu virus gets into the dog, it injects it's RNA into the nucleus of one of the dogs' cells, making it sick (this is how the virus reproduces, it can't make new viruses without a host cell). The human flu gets to the dog, it does the same thing, but it doesn't make the dog sick, because it isn't built right to attack the dog's system.

Let's say, though, for the sake of this example, that somehow, the dog gets in contact with the human flu and the dog flu at the same time. Now there are TWO different forms of RNA floating around in the nucleus. It's getting all jumbled around, and now it's all mixed up. When the RNA returns to the virus that injected it into the nucleus, it will now be a mixture of human flu and dog flu. If this happens enough times, then suddenly, you have a flu with a mixture of the two RNAs, making a 'hybrid' virus that can infect both dogs and humans.

This is how bird flu came about. The flu that affects birds mixed with a type of flu that affects humans, and voila! You get avian influenza!

With e. Coli, it's a bacteria, not a virus, and it works differently from a virus, so it isn't too hard for the bacteria to affect both of dogs and humans!

Answer 3

You are very close.  Canine flu and human flu are different.  Viruses are thought to be more related evolutionarily to their hosts than to other viruses.

Answer 4

I think that you are on the right track.  Flu 'germs' are viruses that enter a cell and commandeer the cell's machinery to replicate themselves until the cell bursts spilling out many copies.  Likely a dog flu virus can not easily commandeer a human cell.  E-coli is a bacteria that potentially can infest many hosts that are not resistant, allowing the bacteria to multiply in the intestinal tract and infect other hosts from excretions.