Merck Manuals: What Patients and Parents Need to Know About Norovirus

RAHWAY, N.J., Feb. 12, 2026 /PRNewswire/ -- Norovirus causes up to 21 million illnesses a year in the United States, with many of the so-called "stomach bug" cases seen in the winter months. Anyone can get norovirus, but children under the age of 5 and adults aged 65 or older are especially at risk.

Understanding the virus can help minimize its impact and its spread to others. In a new editorial from MerckManuals.com, Jonathan Gotfried, M.D. at Bryn Mawr Medical Specialists Association and Main Line Health, details what patients and parents need to know to stay healthy and slow the spread.

Norovirus is highly contagious

Norovirus is very contagious, says Gotfried. Most infections are transmitted by person-to-person contact, particularly through direct or indirect contact with infected stool or vomit. It takes a remarkably small amount of the virus to infect many people, which is why it is so contagious. Gotfried adds that this is why it can easily lead to more widespread outbreaks in contained areas like cruise ships, daycare centers, and restaurants. Each year, there are about 2,500 reported norovirus outbreaks in the United States.

Norovirus does not cause flu-like symptoms

People sometimes call norovirus the "stomach flu," but that's not accurate, says Gotfried. Norovirus typically causes vomiting, abdominal cramps, and diarrhea. People will sometimes have fever, headache, and body aches, but not to the same degree typically seen with the flu. What's more, the flu vaccine will not protect individuals from norovirus. Symptoms like a cough and a high fever may indicate the condition is something other than norovirus.

Norovirus can be life-threatening

On average, norovirus causes 900 deaths in the United States each year, mostly among adults aged 65 and older. Parents should pay close attention to symptoms in children, says Gotfried. Dehydration can occur quickly, particularly in infants.

Washing your hands is the best defense

Washing your hands thoroughly with soap and warm water is the most important step you can take to prevent the spread of norovirus, says Gotfried. Hand sanitizers will not kill norovirus. If you're already sick, washing your hands (especially after using the bathroom and before preparing food) can help prevent the spread to others.

There are other important steps to take to prevent the spread of norovirus, says Gotfried. Practice good food hygiene, including washing hands before touching food, Finally, pay attention to food recalls for purchases you may need to throw away.

To read more of Gotfried's insights on norovirus, visit this editorial on MerckManuals.com.

About The Merck Manuals and MSD Manuals

First published in 1899 as a pocket-sized reference for physicians and pharmacists, The Merck Manual has evolved into one of the world's most trusted and widely-used medical resources. Today, it serves professionals and consumers alike with expert-authored, regularly updated medical content. Available in 16 languages and reaching nearly 250 countries, The Manuals offer far more than text. The website and mobile apps feature an ever-growing collection of videos, podcasts, infographics, and interactive 3D models designed for medical professionals, students, veterinarians, and curious consumers. For over a century, The Merck Manual has been fully committed to making reliable medical knowledge accessible to everyone, everywhere. Access The Manuals online in the United States and Canada at MerckManuals.com, and worldwide at MSDManuals.com. 

About Merck

At Merck, known as MSD outside of the United States and Canada, we are unified around our purpose: We use the power of leading-edge science to save and improve lives around the world. For more than 130 years, we have brought hope to humanity through the development of important medicines and vaccines. We aspire to be the premier research-intensive biopharmaceutical company in the world – and today, we are at the forefront of research to deliver innovative health solutions that advance the prevention and treatment of diseases in people and animals. We foster a diverse and inclusive global workforce and operate responsibly every day to enable a safe, sustainable and healthy future for all people and communities. For more information, visit www.merck.com and connect with us on X (formerly Twitter), Facebook, Instagram, YouTube and LinkedIn.

SOURCE The Merck Manuals