Only Second Case in 20 Years—This Rare Tick-Borne Virus Strikes Newborn on Martha’s Vineyard

On July 24, 2025, five-week-old Lily Sisco was airlifted to Massachusetts General Hospital in Boston after a tick bite led to life-threatening complications. The incident occurred during a family walk on a bike path in West Tisbury on Martha’s Vineyard, where Lily’s mother, Tiffany Sisco, discovered a tiny deer tick—no larger than the tip of a needle—attached to her daughter’s ankle. Though she promptly removed the tick, Lily developed a high fever a week later, leading to an emergency hospital visit.

At the hospital, Lily experienced multiple seizures and was diagnosed with viral encephalitis, a serious inflammation of the brain. Preliminary testing has pointed to the Powassan virus, a rare and potentially deadly tick-borne illness. Health officials confirmed that this is only the second reported case of Powassan virus on Martha’s Vineyard in two decades. According to the CDC, there have been three cases reported in Massachusetts and 24 nationwide so far in 2025.

What is Powassan virus?

Powassan virus is a disease spread by ticks. It can lead to serious brain problems like encephalitis and meningitis. This virus is the only tick-borne flavivirus found in North America, and it is carried by infected deer ticks. It is especially dangerous because it can spread in just 15 minutes after a tick bite, much faster than many other tick-borne diseases. Symptoms of Powassan virus include fever, vomiting, and seizures. In severe cases, it can cause encephalitis or meningitis. The CDC reports that about 10% of severe Powassan cases are fatal, and survivors—especially infants and the elderly—may suffer long-term neurological damage, including memory loss and muscle weakness.

Lily remains in the pediatric intensive care unit, where she is being treated with anti-seizure medications. Her parents, Tiffany and Marcus Sisco, remain by her side, facing difficult uncertainty about her future. Doctors have detected some scarring on Lily’s brain, and while she is showing signs of improvement, her long-term prognosis remains unclear. Tiffany has voiced concern about whether Lily will be able to walk or talk as she grows.

The Sisco family is receiving community support through a GoFundMe campaign to help with medical expenses as Marcus, the family’s sole income earner, stays with Lily full-time.

Health experts urge vigilance in preventing tick bites. Dr. Sam Telford of Tufts University estimates that 1–2% of nymph deer ticks on Martha’s Vineyard carry Powassan. The CDC recommends using EPA-registered repellents with at least 20% DEET, wearing protective clothing, and conducting tick checks after outdoor activities—especially in areas where ticks remain active year-round above 40°F.

Reference:

1. Centers for Disease Control and Prevention. “Clinical Signs and Symptoms of Powassan Virus Disease.” Last modified July 15, 2025. Accessed August 11, 2025.

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