Do all Viruses have the same RNA
A person infected with a strain of a pathogenic virus will have copies of that virus in their body. 

Virus particle genomes could contain a number of substitution, insertion, and deletion mutations. The surface proteins on enveloped and non-enveloped virus copies could contain mutations. Most mutations are deleterious and those particles will not be infectious. 

But the genome sequence of that virus will be largely identical, these mutations aside, and copies will be packaged so as to attempt to reinfect and reproduce.

Actual mutation rates depend on the virus type (RNA, DNA, single- or double-stranded, sense; see Figure 12.1 about the Baltimore classification of viruses), and how it uses reverse transcriptase, RNA, or DNA polymerase to make copies of its genome for use in expression (to make viral proteins) and reproduction (to make viral genomes).

For instance, RNA-dependent RNA polymerase has a lower fidelity rate — makes more copying mistakes — than DNA polymerase. Reverse transcriptase can also introduce mutations when turning the viral RNA genome into DNA, and vice versa. These processes can also introduce errors in expression of membranous or capsid proteins in enveloped and non-enveloped viruses.

The RNA virus family Orthomyxoviridae contains the strains of influenza that infect humans. These are enveloped, negative-sense, single-stranded RNA viruses. They use RNA polymerase to turn their genome into forward-stranded RNA molecules that can act as both mRNA (messenger RNA that is translated into viral proteins) and as a template (again, using RNA polymerase) for making copies of the influenza genome, itself. 

Errors introduced at these two steps will result in copies that are different from the parent.