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We know that viruses are non motile and cannot metabolise, and that it enters the host cells via binding to the receptors. But how exactly it reaches the host

(that is, how it go from the transmission medium (e.g. the aerosols) to actually make contact with the cells in the host)

If it rely on simply diffusion to bump into the host cells' receptors, what makes the odds high enough so that such proliferation strategy is efficient enough to ensure the virus to multiply and proliferate?

In addition, once it has released its DNA into the cell, what helps the DNA to reach the nucleus and not drifting randomly within the cell for a long time, that is, is there exist mechanisms or transportation pathways that actually guide the DNA from the perimeter of the cell through the cytoplasm in the middle and towards the area where the nucleus lie?

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closed as too broad by WYSIWYG, AliceD, jonsca, MattDMo, The Last Word May 29 '15 at 4:23

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ Different viruses have different modes of spreading- some are water borne, some are transported via aerosols, some are sexually transmitted etc. Your question is a little broad. You should narrow it down. $\endgroup$ – WYSIWYG May 28 '15 at 18:35
  • $\begingroup$ A textbook could be written to answer your last question--agree with WYSIWYG that you should narrow your question $\endgroup$ – Luigi May 28 '15 at 18:42
  • $\begingroup$ it is called statistics. Virus or DNA do drift around randomly, but a) there are a lot of DNA/viral particles and b) when virus binds, it stays (so as DNA). And waiting time is not too high $\endgroup$ – Oct18 is day of silence on SE May 28 '15 at 21:48
  • $\begingroup$ @WYSIWYG I have narrowed down the question by elaborating that I am interested in the pathway on how the viral DNA move from the perimeter of the cell through the cytoplasm to the nucleus, and, how once the virus reach the host via aerosol etc. how they actually made contact with the cell to enter them .At the time of the edit, it seems aandreev might have provided an/the explanation and Chris have provide a more detailed explanation $\endgroup$ – Secret May 29 '15 at 1:31
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There are a number of different ways to spread a viral infection. Some viruses sit on surfaces (or infected persons) "waiting" for someone to touch and take them up, this is called smear infection. Other viruses are airborn inside of small droplets distributed by coughing or sneezing. These are inhaled and can then cause a new infection. Other viruses are transmitted through our body fluids (blood, semen) and either need a wound or can be transmitted sexually (for example Herpes or HIV). Other viruses are transmitted by animals which bite humans (Dengue and rabies would be examples here). Have a look into the Wikipedia for more details and examples.

Additionally viruses are produced in vast numbers by their hosts with most viral particles never reaching a new host. This strategy helps a lot to transmit further.s

For entering the nucleus (which is an obstacle) the viruses use the nuclear pore complex (NPC). Depending on what virus tries to enter the nucleus, different strategies are used. Some viruses are too big and release their DNA through the NPC into the nucleus, while others can pass through and some get stuck inside and release their DNA/RNA at this point. A last group uses the time during mitosis when there is no nucleus. See this figure (from here) and also the references below:

enter image description here

References:

  1. Virus strategies for passing the nuclear envelope barrier.
  2. How viruses access the nucleus.
  3. Viruses challenge selectivity barrier of nuclear pores.
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Some virus DNA or RNA might wait cell division to get into nuclei. For example retrovirus genome is not integrated to the genome of the host cell until cells are divided. However, lentivirus does not need to wait for cell division, because one of proteins in lentivirus binding to virus RNA genome has a nuclear transport signal.

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