Norovirus is almost impossible to stop

In a very specific and mostly benign way, it’s starting to feel a lot like spring 2020: the cleanse behind.

“Bleach is my friend now,” says Annette Cameron, MD, a pediatrician at Yale University School of Medicine, who has spent the first half of this week spraying and wiping the potent chemical all over her house. It’s one of the few tools she has to combat norovirus, the nasty gut pathogen that her 15-year-old son has recently been shedding in clumps.

Right now, hordes of people in the Northern Hemisphere are in a similarly bleak situation. In recent weeks, norovirus has spread outbreaks in several countries, including the United Kingdom, Canada and the United States. Last week, the UK’s Health Security Agency announced that laboratory reports of the virus had risen to levels 66 per cent higher than is normal for this time of year. The worst affected are Britons aged 65 and over, who are falling ill at rates “not seen in over a decade”.

Americans may be heading into rough territory, Caitlin Rivers, an infectious disease epidemiologist at Johns Hopkins University, told me, given how closely US epidemiological patterns follow those of the United Kingdom. “NOW,” says Nihal Altan Boneh, a norovirus researcher at the National Institutes of Health. In her private practice, Cameron noticed that the number of cases of vomiting and diarrhea among her patients was steadily increasing. (Other pathogens can cause gastrointestinal symptoms, too, but norovirus is the most common cause of foodborne illness in the United States.)

To be clear, this is more of an annoying problem than a public health crisis. In most people, norovirus causes, at most, a few miserable days of gastrointestinal distress that can include vomiting, diarrhea, and fever, and then goes away on its own; The key is to stay hydrated and avoid spreading it to anyone who is vulnerable — young children, the elderly, immunocompromised. The United States records fewer than 1,000 annual deaths out of the millions of documented cases. In other high-income countries as well, severe outcomes are very rare, although the virus is much more deadly in parts of the world with limited access to sanitation and drinking water.

However, fighting norovirus is not easy, as many parents can attest. The pathogen, which causes the body to expel infectious material from both ends of the digestive tract, is a very dangerous and frustratingly powerful agent. Even the old ready-made COVID system, a spray of hand sanitizer, doesn’t work against it — the virus is encased in a tough protein shell that makes it insensitive to alcohol. Some have estimated that ingesting as few as 18 infectious units of virus could be enough to infect a person, “and typically billions are discarded,” says Megan Baldridge, a virologist and immunologist at Washington University in St. Louis. At its most extreme, one gram of feces — roughly the weight of a jelly bean — could contain up to 5.5 billion infectious doses, enough to send the entire population of Eurasia running to the toilet.

Unlike influenza and RSV, two other pathogens that have bounced back to prominence in recent months, norovirus primarily targets the gut, spreading particularly well when people swallow viral particles released in someone else’s vomit or stool. (Despite the “stomach flu” moniker, norovirus is not an influenza virus.) But direct contact with those substances, or the food or water they contaminate, may not be necessary: ​​Sometimes people vomit with such force that the virus spreads; Toilets, especially those without a lid, can send up plumes of infection like an Air Wick from Hell. And Altan-Bonnet’s team has found that saliva may be an unpresentable reservoir for norovirus, at least in laboratory animals. If spit detection applies to humans, talking, singing, and laughing up close could be risky, too.

Once norovirus particles are released into the environment, they can linger on surfaces for days — making frequent hand washing and disinfecting surfaces key measures to prevent spread, says Ibukun Kalu, a pediatric infectious disease specialist at Duke University. Handshakes and shared meals tend to get dicey during an outbreak, along with frequently touched items like utensils, doorknobs, and phones. A 2012 study cited a woven plastic grocery bag as the source of a small prevalence among a group of teenage soccer players. The bag had just been sitting in the bathroom one of the girls had used when she had fallen ill the night before.

Once the chain of norovirus transmission begins, it can be very difficult to break it. The virus can spread before symptoms start, and then for more than a week after they resolve. To make matters worse, immunity to the virus tends to be short-lived, lasting only a few months even against a genetically identical strain, Baldridge told me.

Day care, cruise ships, schools, restaurants, military training camps, prisons, and long-term care facilities can be common places for norovirus to spread. “I’ve done research with the Navy, and it passes like wildfire,” says Robert Frink, director of the Center for Vaccine Research at Children’s Hospital of Cincinnati, often infecting more than half of people on tightly packed ships. Families are also highly vulnerable to transmission: once the virus arrives, the entire household is almost certainly infected. Baldridge, who has two young children, told me her family has survived at least four bouts of norovirus in the past several years.

(Pause for some irony: Despite the infectiousness of norovirus, scientists only succeeded in cultivating it in laboratories only a few years ago, after nearly half a century of research. When researchers design challenge trials, for example, to test new vaccines, they still need to dose volunteers with norovirus extracted from a patient’s stool, an anomaly that’s been around for more than 50 years.)

The spread of norovirus should not be taken for granted. Some people are lucky: Nearly 20 percent of Europe’s population, for example, is genetically resistant to common norovirus strains. “So you can hope,” Frink told me. For the rest of us, it’s about cleanliness. Altan-Bonnet recommends diligent hand washing, as well as masking to ward off droplet-borne viruses. Patients should isolate themselves if they can. She told me, “Keep your saliva to yourself.”

Rivers and Cameron have both successfully stopped the virus in their homes in the past; Maybe Cameron pulled it off again this week. The family vigorously cleaned their hands with hot soapy water, wore disposable gloves when touching shared surfaces, and exploited the virus’s susceptibility to harsh chemicals and heat. When her son vomited on the floor, Cameron sprayed her with bleach; When he vomited on his comforter, she blew it twice in the washing machine on sanitizing setting, then put it in the dryer on very high heat. Two days after their son’s illness ended, Cameron and her husband apparently escaped unharmed.

Norovirus is not new, and this won’t be the last time it will strike. In many ways, “this is back to basics,” says Samina Bombra, MD, medical director of infection prevention at Riley Children’s Hospital. After three years of COVID, the world is used to thinking of infections in terms of the airways. “We need to recalibrate, and remember there are other things out there,” Bombera told me.


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