Epidemiology

Marine virus may account for some unexplained human illnesses

Last Updated: 2006-05-30 14:44:01 -0400 (Reuters Health)

By Will Boggs, MD

NEW YORK (Reuters Health) - Infection by the marine virus genus Vesivirus may be behind some otherwise unexplained human illnesses, according to a report in the May issue of the Journal of Medical Virology.

"We now have very good reagents (antigen, monoclonal antibody, hybridization probe and primer sets), which allow us to diagnose with considerable confidence vesiviral infections involving most of the known vesivirus variants," Dr. Alvin W. Smith from Oregon State University, Corvallis, told Reuters Health. "There is an extensive array of conditions where evidence exists - sometimes very thin - implicating vesiviral infections."

Dr. Smith and colleagues tested sera from four groups for antibodies to Vesivirus: blood donors whose units were cleared for donation, blood donors whose units were rejected because of elevated alanine aminotransferase (ALT) levels, patients with clinical hepatitis of unknown but suspected infectious cause, and patients with clinical hepatitis of unknown cause but associated with blood transfusion or dialysis.

The prevalence of antibody to Vesivirus was higher in units rejected because of high ALT levels (21%) than in normal donor units (12%), the authors report. The highest prevalence (47%) was seen in patients with hepatitis associated with transfusion or dialysis.

Cases of non-A-E hepatitis had an estimated antibody prevalence (19%) similar to that of the high-ALT donors, the results indicate, whereas those with hepatitis B or C virus infection had an estimated prevalence (10%) similar to that of healthy donors.

The researchers also found that of 112 sera tested, 11 (9.8%) yielded polymerase chain reaction amplicons whose nucleotide sequence was related to known Vesivirus.

"The Vesivirus strains causing Vesivirus viremia in this study were closest by genome sequence comparison to SMSV, marine Vesivirus," the investigators note. SMSV stands for San Miguel sea lion virus

"The present findings indicate a broader potential for Vesivirus infection and, perhaps, illness in humans than previously recognized," the researchers conclude. "A finding of subclinical viremia and the detected highest seroprevalence in cases of clinical hepatitis associated with transfusion or dialysis suggest that blood exposure that may have led to hepatitis also could lead to higher exposure to Vesivirus."

Vesiviruses are extremely versatile pathogens, Dr. Smith explained. "One of their hallmarks is the success with which they adapt to new host species and then spread through that species. They routinely do what everyone hopes the bird flu will not do, that is, spread from the reservoir species directly into a new target species and then spread individual-to-individual through the new host."

Among the conditions for which there is at least preliminary evidence implicating Vesivirus, Dr. Smith said, are vesicular dermatitis resembling Herpes type 1 and hand-foot-and-mouth disease, spontaneous abortion, encephalitis, and such other diverse conditions as hemorrhagic/disseminated intravascular coagulation, myocarditis, pneumonia, pancreatic infection, newborn thymic involution, and diarrhea.

"We want to further define the activity of this newly recognized but versatile viral pathogen in the human health arena by partnering with interested diagnosticians and researchers and sharing reagents and samples," Dr. Smith added.

J Med Virol 2006;78:693-701.