Yellow fever is a disease that can result in symptoms ranging from fever to severe liver damage. Found in South America and sub-Saharan Africa, each year the disease results in 200,000 new cases and kills 30,000 people. About 900 million people are at risk of contracting the disease.
Now a research team led by a biomedical scientist at the University of California, Riverside has determined that the yellow fever virus, a hemorrhagic fever virus, replicates primarily in the liver. Therefore, other organ failures that often follow in people with the disease are due to secondary effects.
When the virus targets the liver, it replicates rapidly causing significant damage to liver cells. In the process, inflammatory cytokines – proteins secreted by cells especially of the immune system – are made in massive amounts, which soon gain access to the blood stream. These cytokines are most likely responsible for the damage to distant organs, the research team’s findings suggest.
The research team also identified a clinical parameter that could greatly help in managing yellow fever cases.
“Yellow fever causes severe loss of lymphocytes,” said Ilhem Messaoudi, an associate professor of biomedical sciences in the UC Riverside School of Medicine, who led the research project. “This process, called lymphopenia, occurs before any measurable changes in liver enzymes can be detected – that is, about a day or so before we see changes in the liver. It could provide an earlier clinical outcome measure of subsequent disease severity, giving doctors a good prognostic tool for offering more aggressive supportive care for these patients.”