Threat assessment

If you’ve never heard of Powassan virus (POWV), the cause of a tick-borne disease first discovered in the mid-20th century, you’re not alone. Despite the severity of its symptoms, it has received little attention—from scientists or the public—because of its rarity.

But in recent years, incidence of the sometimes-fatal disease has been increasing, especially in the Great Lakes and northeast regions of the US. Now, with funding from the National Institutes of Health (NIH), researchers from the University of Minnesota College of Veterinary Medicine (CVM) are hoping to fill gaps in the knowledge that are critical for future prediction, prevention, and control of the disease.

POWV is now considered an emerging public health threat because its spread has been associated with an aggressive, human-biting species of tick called Ixodes scapularis—sometimes referred to as the deer tick or blacklegged tick. Initial symptoms, including fever, headache, vomiting, and generalized weakness, appear within 4 weeks of being bitten by an infected tick. The disease can progress to brain encephalitis and meningitis (inflammation of the brain and membranes around the spinal cord), and can cause seizures, speech problems, and paralysis. POWV is fatal in about 10% of people, and 50% experience long-term neurological problems. There are currently no vaccines or treatments for POWV.

Enter Matt Aliota, associate professor at CVM, who recently received the 5-year, $3.5 million grant from the NIH to help develop foundational knowledge of the disease. Aliota’s project will combine field and laboratory studies to evaluate how genetic variation in tick and POWV populations affects the virus’s evolution and spread.

Focusing on Minnesota and New York, two epicenters of the disease’s increasing transmission, Aliota’s team will first assess the distribution and genetic structure of POWV in those states. They’ll then work to evaluate how regional variation in the virus’s genetics affects and is affected by each region’s tick populations in terms of the ticks’ vector competence—in other words, their ability to transmit the infection. They will also evaluate how the virus’s genetics impacts disease outcomes in humans and attempt to identify the hosts that maintain this virus in nature. 

To access all the samples needed for this research, the team will work with the Minnesota Department of Health to expand on existing POWV surveillance activities in Minnesota, which will involve collecting infected ticks to sample from field locations around the state. In New York, they will partner with the New York State Department of Health, which has robust POWV surveillance in place, including an archive of existing samples and a program for ongoing collection.

In addition to the Minnesota and New York State Departments of Health, Aliota’s team will collaborate with researchers from the Wadsworth Center for support studying tick vector competence and virus genetics, and the University of Pennsylvania for support studying tick population genetics.

"POWV is transmitted by the same tick species that transmits the pathogens that cause Lyme disease, and other related pathogens. If POWV continues on a similar trajectory as these other pathogens, it could become a major public health problem,” said Aliota. “The work we are doing is aimed to be proactive to understand the magnitude of the potential risk so POWV does not catch us off guard from a public health standpoint."