Earth life is aquatic. Our chemistry happens immersed in water. When life left the oceans, living beings like you and I took the water with us. We are walking bags of water: approx 75% by weight.
Of course martian life could be different than terran life, and that would be interesting too. But there are reasons to suspect that liquid chemical reactions was necessary at the genesis of life, and water is a uniquely optimal liquid for this purpose.
A martian virus is unlikely to do anything to your immune system. For one thing it is unlikely that the virus would even use the same genetic codes (A C T G) as terran DNA, unless we share a common ancestor, and even in that case it wouldn't do anything against you & your immune system would eventually create an antibody and wipe it out. We fear things like bird flu and swine flu because they develop in close proximity to humans in analogous systems, honing attack vectors specifically targeting some weakness of the animal body. An alien virus would likewise be good at attacking aliens, not us.
Of course martian life could be different than terran life, and that would be interesting too. But there are reasons to suspect that liquid chemical reactions was necessary at the genesis of life, and water is a uniquely optimal liquid for this purpose.
A martian virus is unlikely to do anything to your immune system. For one thing it is unlikely that the virus would even use the same genetic codes (A C T G) as terran DNA, unless we share a common ancestor, and even in that case it wouldn't do anything against you & your immune system would eventually create an antibody and wipe it out. We fear things like bird flu and swine flu because they develop in close proximity to humans in analogous systems, honing attack vectors specifically targeting some weakness of the animal body. An alien virus would likewise be good at attacking aliens, not us.