Do the viruses damage our cells directly?

[mktsgm]

TL;DR

How do viruses or their replication cause injury to our cells directly? Simply why do we have to worry about virus infection?

Viruses when they infect us, enter the target cells, hijack the machinery and start producing their own Copy and eject out. So what?

Question is, how do they directly cause injury to our cells? Do they harm injury our cells directly?

Of course we know that our own immune system which becomes active unleashes the most of the damage.

My question is, do the viruses cause us harm directly?

 

[jedishrfu]

Viruses invade our cells take over the protein generation machinery and begin to produce more viruses then they cause the cell to commit aptosis (ie cell death) to be released back into the wild to invade more cells and repeat the process. Meanwhile your body attempts to thwart the viral invasion by identifying and encapsulating the viral particles to prevent further infection.

https://www.khanacademy.org/science...system/v/viral-replicaiton-lytic-vs-lysogenic

 

[sysprog]

I think that this explanatory vid is pretty good:

 

[DaveC426913]

If I understand correctly, the Covid-19 virus in particular excites the immune response, triggering what's called a cytokine storm - essentially an allergic overreaction - immune cells flood the region. This causes swelling and inflammation - critically in the air ways. Covid-19 sufferers tend to die of pneumonia-like afflictions - ultimately choking on the fluid build-up in their restricted airways.

This is just off the top of my head from osmotic reading - don't take it as gospel.

 

[mktsgm]

"It is the immune system response that is causing all the troubles like cell lysis, apoptosis, necrosis, cytokine storm and what not... in the event of an infection.

Without immune system in place, the cell damage may not occur even in the presence of viruses. Viruses per se do not cause any damage, other than misusing cell machinery to replicate itseld."

This is my understanding. Is this assumption right? (Of course we may not have a system in Vivo that is sans immune system in place. This is a question just to understand the mechanism of cell/tissue damage post infection.

Is the infection-induced damage mechanism similar for bacteria, fungus too?

 

[DaveC426913]

Is the infection-induced damage mechanism similar for bacteria, fungus too?

Partly, but not completely.

I'm think that bacteria directly cause damage by causing cell breakdown, as well as - when they multiply out of control - their waste products are toxic.

I think fungi only affect the outer parts of the body - and, again it's often their waste products that irritate and otherwiie wreak havoc in the tissues.

see caveat in sig line: *

 

[atyy]

"It is the immune system response that is causing all the troubles like cell lysis, apoptosis, necrosis, cytokine storm and what not... in the event of an infection.

Without immune system in place, the cell damage may not occur even in the presence of viruses. Viruses per se do not cause any damage, other than misusing cell machinery to replicate itseld."

This is my understanding. Is this assumption right? (Of course we may not have a system in Vivo that is sans immune system in place. This is a question just to understand the mechanism of cell/tissue damage post infection.

Is the infection-induced damage mechanism similar for bacteria, fungus too?

Viral infection in cell culture shows that it can cause cell death even without an immune system.

As you and others have mentioned, in the presence of an immune system, there can be additional or different effects.

https://jvi.asm.org/content/81/12/6346

https://www.nature.com/articles/s41419-018-0917-y

 

[willem2]

Is the infection-induced damage mechanism similar for bacteria, fungus too?

using lysis to get out the viruses is common in bacteria but not plants/animals.

For example Coronavirus uses the cells mechanism for transporting out proteins (exocytosis). Influenzavirus uses budding at the cell membrane, where the cell membrane bulges out around the virus, until a bubble of it separates.
Exit strategy for bacteria, https://viralzone.expasy.org/4018
plants https://viralzone.expasy.org/5656
animals https://viralzone.expasy.org/1076

 

[Laroxe]

When a virus invades a cell it takes control of the cell machinery to produce more viruses, this means the cell is no longer functioning as it should. Cells often have fail safe mechanisms that recognise something has gone wrong and these can trigger apoptosis, if this mechanism is bypassed cells may express a particular protein on its surface that act as a distress signal, this triggers immune cells to kill the cell. If these mechanisms don't work the virus continues to be produced in the cell until they burst out, ready to invade other cells, this process usually kills the cell. The reason that an infected cell is destroyed is that it prevents further viral reproduction and allows the damaged cell to be replaced. While our immune system can be a bit overzealous the complication usually referred to as a cytokine storm occurs when there is a large number of infected cells all sending out distress signals in a desperate attempt to control the infection. It causes widespread apoptosis, even in uninfected cells and the immune cells become increasingly less discriminating, this can be very damaging and is one of the reasons some areas in the body are protected from this effect (like the brain).
This is a rather long but brilliant description of how cells work and uses the example of flu to show how our immune response tries to protect them, its really worth watching.