Non-A, XXXX : evolving epidemiologic and clinical perspective.

@entity1 @entity97 @entity82 @entity1956 @entity409 @entity3619 @entity99
Evidence for the existence of @entity1 @entity99 agents besides HAV and @entity97 is compelling. Transmitted predominantly by transfusion and percutaneous inoculation, the type of NANB @entity99 encountered most frequently is epidemiologically similar to type B @entity99 . NANB @entity99 accounts for more than 90% of TAH, but can be transmitted by nonpercutaneous routes as well. Approximately 15 to 30% of @entity99 cases are attributable by serologic exclusion to NANB @entity99 agents, and, in addition, there is an epidemic form of NANB @entity99 that resembles @entity99 epidemiologically in its transmission by the enteric route. Clinical features of the predominantly percutaneously transmitted forms of NANB @entity99 are similar to those of @entity1956 , but tend to be less severe during acute illness, on the one hand, but to lead more frequently to @entity3619 , on the other; 40 to 60% of @entity1 with TAH have chronic elevations of aminotransferase activity, often in an episodic, fluctuating pattern. CAH can be identified histologically in a majority of @entity1 with chronic NANB TAH. Despite a relatively quiescent course, progression of such chronic cases may be quite insidious; @entity82 occurs in 10 to 20% of @entity1 with @entity3619 after acute TAH. The frequency of @entity409 after nonpercutaneously acquired sporadic NANB @entity99 tends to be lower, on the order of 10% or less, and @entity3619 has not been recorded after the epidemic type of NANB @entity99 . Evidence supports the existence of an asymptomatic @entity3619 carrier state that is several-fold more frequent than the chronic @entity97 carrier state. Neither viruses nor virus markers have been described that fulfill accepted criteria reproducibly for a specific causal association with NANB @entity99 ; on the other hand, evidence suggests (but does not prove) the existence of two different blood-borne NANB @entity99 agents and, in addition, an enterically transmitted NANB @entity99 agent. Effective therapy for and immunoprophylaxis against NANB @entity99 are lacking. Until specific screening tests are developed, interim screening based on indirect, nonvirus-specific tests may be the only practical approach to minimizing the frequency of NANB @entity99 after transfusion. Identification of virus-specific serologic markers remains a high priority.
