How do viruses cause diseases

[Navin]

I know in general how viruses replicate.However i am still unclear how they cause diseases.

According to Campbell, some viruses may secrete toxins which causes the symptoms. How do viruses produce the toxin?

Also, specifically for the influenza virus, what does it do that causes humans to have runny noses and a high temperature? Is it because the immune system is at work here?

[LilKim]

i would guess that viruses are toxic because their viral DNA has genes that encode toxic substances .. that kill cells (or makes them sick) in most situations.

I know that the fever is due to an immune response. Cells of the immune system secrete "stuff" that cause your body to thermoregulate differently. Most "bugs" work optimally at normal body temp.. so when your body raises the temp. a little ... it will have a "slowing" effect on the invading "bug" ... I would guess that a runny nose is also a defense mechanism to remove "stuff" from your air-ways and nasal passages (but that's just a guess)

HOWEVER!!! there are "bugs" that are pyogenic ... These bugs will cause your temperature to increase to dangerously high temperatures.

hope this helps.!
- KIM

[seaseasea]

i think there are many mechanisms used by viruses to result in deaeases.it also can secretes peptide which has a role in cell signl transduction
pathway.

[LilKim]

Viral genes are transcribed and translated by hijackin host cell machinery (RNA polymerases and ribosomes) to produce toxins.

Influenza ... when the cells of the immune system come in contact with influenza the cells become activated .. thereby stimulating/activiating other immune system cells. A part of this activation process involves the secretion of cytokines and chemicals that generallyy make you "feel sick"... and I know that the cytokines or chemicals can influence body temperature (thereby raising temp. and giving you a fever).

the runny nose thing... not sure? it's just a mechanical way or removing stuff from mucous membranes.

[victor]

Virus as an obligate intracellular pathogen will cause cytopathologies to its target in certain mechanisms....the things that I know is about HIV virus (for example):
this HIV virus will encode its protein via viral mRNA and it also cause frameshift mutation in certain place of host's DNA which will result in some defects into the host cell.

[Navin]

Thanks people. When i get more info, i will post them here.