Winter months consistently produce the highest numbers of Norovirus outbreaks, but early reports suggest that the bug may be striking a particularly large number of victims this season. In the United Kingdom, the number of confirmed Norovirus cases has risen to 72 percent higher than this time last year. In total, 3,877 citizens have been confirmed with infections, up from 2,255 a year ago. But for every confirmed case of Norovirus, experts estimate that another 288 cases go unreported. That means that more than 1.1 million UK citizens may have already suffered bouts with the bug, which can include vomiting, diarrhea, nausea and abdominal pain. The Canadian province of British Columbia has also seen its greatest number of November and December Norovirus cases since 2006. Some healthcare facilities in the region have closed off portions of their premises for disinfection in attempts to prevent further spread of the virus. Canadian health officials told The Globe and Mail that this year’s spike in winter Norovirus is likely due to a new strain entering global circulation. New strains of the bug typically emerge every three or four years.

Norovirus infections are predominantly transmitted via person-to-person contact, but can also be contracted through contact with contaminated food, water or surfaces. In otherwise healthy adults, symptoms generally resolve themselves within 24 to 48 hours, and are sometimes mischaracterized as the “stomach flu” or the “24-hour flu.” Infections may be more severe in children, the elderly or adults with compromised immune systems. Whether a spike has also occurred in the United States remains to be seen. News reports have highlighted a number of outbreaks in recent weeks, but hard numbers do not yet exist for nationwide infection rates. One medical center in Portland, Ore. has seen at least 75 cases in its emergency room since Christmas, according to local news station KGW. At least 167 diners fell ill in mid-December after eating at a Golden Corral buffet-style restaurant believed to be at the center of a Norovirus outbreak in Casper, Wyo. On Thursday, a luxury Caribbean cruise liner docked back in New York after its 12-night cruise hosted an outbreak that sickened at least 220 of the 3,868 people on board. Health officials say a single infected passenger could have started the entire outbreak. Another 220 of 4,424 people aboard a similar cruise fell ill just days earlier. Days before that, more than 400 people fell ill on a 10-day Baltic cruise. And in Japan, at least five elderly patients have died in recent weeks as Norovirus outbreaks spread through regions of the country, infecting hundreds. In the meantime, researchers at the University of Cambridge are working with “Vomiting Larry,” a “humanoid simulated vomiting system” currently hurling up vomit infected with simulated Norovirus. The study will help define how far individual virus particles can travel during vomiting, as the virus can be transferred through the air, and fewer than 20 virus particles pack enough punch to infect a person. Researchers may also gain a better understanding of how well the infamously evasive virus avoids cleaning attempts. According to the U.S. Centers for Disease Control and Prevention, Norovirus sickens an estimated 21 million Americans each year, contributing to 70,000 hospitalizations and 800 deaths. While most cases result from human contact, Norovirus also remains the most common source of foodborne illness in the U.S. and is regularly associated with leafy greens, fresh fruits and shellfish.