A83Mosquito-borne viral encephalitis

A83 is the ICD-10-CM diagnosis code for mosquito-borne viral encephalitis. It belongs to block A80-A89 (viral and prion infections of the central nervous system) and chapter 1 (certain infectious and parasitic diseases). It is a header code, so it can't be reported by itself; one of its 9 subcodes must be used instead.

To report this condition, pick the subcode that matches the documentation: A83.0 (encephalitis), A83.1 (encephalitis), A83.2 (encephalitis), A83.3 (encephalitis), A83.4 (encephalitis), A83.5 (encephalitis), A83.6 (disease), A83.8 (encephalitis) and 1 more.

The conditions in its Excludes2 note aren't part of A83, but may be coded alongside it if the patient has both: Venezuelan equine encephalitis (A92.2), West Nile fever (A92.3-) and West Nile virus (A92.3-).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.