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The “Ferrari of viruses” is making its presence felt across the Northern Hemisphere, causing a surge in outbreaks of the highly contagious norovirus. Known for its rapid spread and explosive symptoms, norovirus is racing through cruise ships, nursing homes, and households, sending thousands to hospitals and, in rare cases, leading to fatalities.
In the U.S., the virus has been particularly active, with 91 outbreaks reported in the first week of December 2024, surpassing the previous high of 65 outbreaks in the same week over the past decade. Levels of norovirus RNA in U.S. wastewater are also notably higher than last year, indicating a larger-than-usual spread.
“It’s shaping up to be an intense norovirus season,” says Lisa Lindesmith, a researcher at the University of North Carolina (UNC) at Chapel Hill. The rise in cases could be attributed to a new variant of the virus, alongside a return to pre-pandemic activities such as cruises and gatherings, which may have contributed to increased transmission.
Norovirus is particularly known for thriving in colder climates and is highly resistant to disinfectants. It causes sudden, severe gastrointestinal symptoms—vomiting and diarrhea—usually lasting for a day or two. However, even after recovery, individuals can continue shedding the virus for weeks, potentially infecting others. Its persistence on surfaces and transmission through contaminated oysters further complicate efforts to control the outbreaks.
Health authorities worldwide are raising alarms. In the U.S., norovirus is the leading cause of hospitalization due to diarrheal disease, with young children and the elderly particularly vulnerable. The virus is responsible for an estimated 200,000 child deaths annually in the developing world. Though the mortality rate is lower in wealthier nations, the financial burden is significant, with global losses totaling an estimated $60 billion annually due to missed work.
One of the most concerning developments this winter is the emergence of the GII.17 variant, which is quickly gaining ground. The U.S. Centers for Disease Control and Prevention (CDC) has reported that this variant now accounts for 70% of viral isolates sequenced in the second half of 2024. Its rise, which includes significant mutations from previous strains, has made it a formidable force in the current outbreak. In Europe, the U.K. and Netherlands are also seeing a dominance of GII.17.
“The immunity levels in the population were likely reduced after social distancing during the pandemic,” explains Ralph Baric, a renowned researcher at UNC. “This lack of exposure may have paved the way for a bigger resurgence as things returned to normal.”
Despite its widespread impact, norovirus remains difficult to combat due to its ability to rapidly mutate, evading the immune system and making vaccine development a major challenge. Although several vaccine candidates have been under development, progress has been slow. A promising vaccine from HilleVax failed in a trial in infants, and while companies like Moderna and a Chinese firm, Zhifei, are continuing trials, a reliable, widely available vaccine is still years away.
Scientists stress that even if a vaccine is developed, it may not fully prevent infection or transmission. “Norovirus is one of the most infectious viruses in nature,” says Lindesmith. “It’s unlikely that any vaccine will stop all cases, and regular boosters may be required.”
The need for effective treatments and prevention strategies is pressing. While most people recover from norovirus within a day or two, the virus can cause severe illness in certain populations, and its ability to spread quickly through communities remains a global concern. A vaccine could not only reduce the severity of symptoms but also slow transmission, potentially saving lives and preventing the virus from wreaking havoc on daily life.
As the winter surge continues, health experts are urging heightened awareness and caution. In the meantime, the ‘Ferrari of viruses’ shows no sign of slowing down.
