Retroviruses are single stranded RNA viruses that undergo DNA phase during their replication. All the retroviruses contain reverse transcriptase enzyme and are capable of integrating with the host genome. Currently retroviruses are divided into 7 classes based on their biological and molecular properties. In general they are classified into three categories –

I. Oncoviruses

II. Lentiviruses

III. Spumaviruses

 

I. Oncoviruses

These viruses have long incubation period and are associated with immune deficiencies. Occasionally encephalopathy and arthritis may also be evident eg human immuno deficiency virus (HIV), feline immuno deficiency virus (FIV), and simian immuno deficiency virus (SIV).

 

II. Lentiviruses

These viruses have long incubation period and are associated with immune deficiencies. Ocasionally encephalopathy and arthritis may also be evident eg human immuno deficiency virus (HIV), feline immuno deficiency virus (FIV), simian immuno deficiency virus (SIV).

 

III. Spumaviruses

Spuma stands for foamy. The virus causes vacuolation and froth like appearance in infected cells.eg simian foamy virus (SFV).