New treatment options may soon exist for people with yellow fever, a mosquito-borne illness that claims the lives of 30,000 people annually. A research team headed up by Ilhem Messaoudi, associate professor of biomedical sciences at UC-Riverside’s School of Medicine, feels they may have identified a way to predict which cases of the disease will turn potentially deadly.
Yellow fever affects more than 200,000 people annually in Latin America and Africa, with 50 percent of untreated, severe cases resulting in mortality. The World Health Organization (WHO) indicates that more than 900 million people live in areas where this virus is endemic, and over the last few years, the number of yellow fever cases has seen an increase.
Unfortunately, though similar to other hemorrhagic diseases in tropical environments, yellow fever has remained relatively mysterious to experts, and there is no medication designed to specifically treat it. During its early phases, yellow fever can be difficult to identify, and approximately 15 percent of patients will experience a more severe form of the disease within 24 hours of infection. This makes timely treatment important in order to prevent organ damage or death.
Vaccinations against yellow fever have been successful, but those vaccinations have difficulty reaching many impoverished, isolated areas in Latin America and Africa where people are most affected.
“While it is true there is a highly effective vaccine, it remains extremely challenging to get comprehensive vaccine coverage in sub-Saharan Africa and Latin America,” Messaoudi told MNT. “Moreover, the vaccine works well if you are between one and 55 years old. It is not safe for babies or the elderly, who could develop yellow fever from the vaccine.”
The trouble with yellow fever, according to the experts, is that it wants to replicate in the liver. In people who develop potentially-deadly yellow fever, this replication process damages the liver cells and causes them and immune cells to release large amounts of inflammatory protein known as cytokines into the bloodstream. These cytokines are what start to damage other organs in the body.
Prior to this chain of events, however, there appears to be a warning sign Messaoudi and his team were able to identify. Approximately 24 hours before negative changes in the liver are seen, there is a drastic drop in white blood cells known as lymphocytes.
“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,” explained Messaoudi. “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.”
In other words, as soon as doctors see a sharp decline in the number of white blood cells in a patient with yellow fever, they know the disease is likely entering a severe stage, and supportive treatment can be started before the body begins to suffer damage.
This is good news for people able to receive treatment for yellow fever, but WHO notes regions where yellow fever mortality rates are the highest are generally those areas where supportive care is not available.