and viruses?

Viruses are notorious, like a number of bacteria, as carriers of infectious diseases. Anyway while bacteria are sensible to antibiotics action, viruses are not.

Are viruses a different kind of microorganisms?

It is difficult to answer this question. Consider that in 2012 two different studies were published in the prestigious scientific journal “ Nature”. The first one entitled “Ten reasons to exclude viruses from the tree of life” and the second one entitled “Reasons to include viruses in the tree of life”

Even today viruses are thought of as being in a gray area between living and nonliving.

I can only give you some information.  They are generally smaller then every cell type ranging their size from 10- to 400 nm 

( millionths of a mm) and all are obligate intracellular parasites, Indeed viruses do not posses biochemical and biosynthetic structures for their replication.

All viruses contain nucleic acid, either DNA or RNA (but not both), and a protein coat, which encases the nucleic acid. 

Some viruses are also enclosed by an envelope of fat and protein molecules... 

The external coat contains special sites on its surface that allow the virus  to attach to a host cell, and provides proteins that enable the virus to penetrate the host cell membrane. 

Viral populations to grow use the machinery and metabolism of a host cell to produce multiple copies of themselves, and they assemble in the cell.....

So, when infected, the host cell is forced to rapidly produce thousands of identical copies of the original virus.

 Attachment is a specific binding between viral capsid proteins and specific receptors on the host cellular surface. This specificity determines the host range of a virus. ... This mechanism has evolved to favour those viruses that infect only cells in which they are capable of replication.
Unfortunately viruses are sometimes able to mutate and change their target cells.

   

Really in many cases nature is beyond imagining!!!

Indeed viruses behavior, whether they are living organisms or not, could give inspiration for science-fiction tales.

 Imagine, for example,  an alien intelligence  that, entering a body, makes maximum use of it up to its self-destruction.
 Or imagine an alternative program entering into the computer of a car factory forces the machinery to produce instead tanks?
Viruses act like this: Indeed we speak also  of computer viruses.

Digressions apart, why viruses are antibiotic-proof? Because antibiotics act deteriorating the bacterial metabolism but are ineffective on viruses because they  do not possess a their own metabolism!!

Only antibodies produced by the infected organism are able to counteract viruses: for this reason it is possible to recover from a viral disease, at present even from covid-19, without specific treatments (that there are not yet).
A vaccine is hoped for the latter new virus that, like all vaccines, could induce specific antibodies production from the target organisms allowing them to stop the virus entrance at the first contact.