Yellow fever is a single stranded RNA virus (ssRNA)

West Nile virus is a virus with a single stranded RNA genome (ssRNA)

These are the retro single-stranded RNA. These viruses make DNA from RNA using an enzyme called reverse transcriptase. One of the most famous example of the ssRNA-RT virus is the HIV virus.

The organism that causes polio is a virus.

A RNA virus is an virus that contains either an single-strand of RNA (ssRNA) or a double strand of RNA (dsRNA) as their genome.

Some families of RNA viruses include: Reovirus (dsRNA), Picornavirus (ssRNA), Coronavirus (dsRNA), Flavivirus (dsRNA) and Togavirus (dsRNA)

As for type, I'm unfortunately unsure as to what you're referring to.