Two groundbreaking discoveries by USC researchers could lead to medications and a vaccine to treat or prevent a hemorrhagic fever transmitted by a new tick species before it spreads across the United States.

In the latest issue of Nature Microbiology, researchers describe the molecular mechanisms used by the virus to infect and sicken humans, a puzzle that has stumped scientists since the disease emerged in rural China in 2009.

In a related discovery published in Nature Microbiology last month, researchers at USC and in Korea found that aged ferrets with the virus exhibit symptoms similar to those seen in older humans, while young ferrets show no clinical symptoms. An animal model in which to study the virus, a crucial tool in vaccine or drug discovery, has been elusive, until now.

“The ticks are already in the United States,” said Jae Jung, the study’s senior author and chair of the Department of Molecular Microbiology and Immunology at the Keck School of Medicine of USC. “If they start spreading the virus, it will be a major problem. I started studying this virus five years ago because once it appeared in China, I knew it would eventually appear in the United States.”

The findings come at a time when health officials are increasingly concerned about the growing danger of tick-borne illnesses. In the United States, Lyme disease accounts for most cases, but other illnesses are on the rise. The total number of reported cases has more than doubled in the past 13 years, according to the U.S. Centers for Disease Control and Prevention.

The new threat comes in the form of a bug new to North America — the Asian longhorned tick, Haemaphysalis longicornis. It’s a tiny, parasitic arachnid that’s a major livestock pest in East and Central Asia, where it thrives under temperate conditions. After a blood meal, females drop off their host to produce 2,000 eggs at a time, with or without the help of a male.

It can transmit severe fever with thrombocytopenia syndrome, an illness that causes nausea, diarrhea and muscle pain. The illness is often lethal, killing up to 30 percent of hospitalized patients. The virus depletes blood platelets as it replicates, which prevents clotting and leads to hemorrhage similar to Ebola virus infection.

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