Norovirus and COVID-19 are widespread, highly contagious viral illnesses. Both share overlapping symptoms and rapid spread, but differ in how they affect the body and require distinct prevention and management. Understanding these differences helps in recognizing each illness and taking appropriate action.
How Norovirus and COVID-19 Spread
Norovirus primarily spreads through the fecal-oral route, transmitted when microscopic fecal particles from an infected person are inadvertently ingested. This can occur through direct contact with an infected individual, consuming contaminated food or water, or touching contaminated surfaces and then touching one’s mouth. It spreads quickly in crowded, enclosed environments like cruise ships, schools, and healthcare facilities. A very small number of norovirus particles, between 18 and 1000, can be enough to cause infection.
COVID-19, caused by SARS-CoV-2, primarily spreads through respiratory droplets and aerosols released when an infected person coughs, sneezes, talks, or breathes, which can then be inhaled or land on mucous membranes. While less common, transmission can also occur by touching contaminated surfaces and then touching the face. The risk of COVID-19 transmission is higher in crowded, poorly ventilated indoor spaces, where respiratory particles can linger and accumulate.
Key Differences in Symptoms
Norovirus typically causes acute gastroenteritis, commonly known as the “stomach bug.” Symptoms usually appear suddenly, within 12 to 48 hours after exposure, and primarily include nausea, vomiting, watery diarrhea, and stomach cramps. Some may also experience a low-grade fever, headache, or body aches, but these are less prominent. The illness is generally brief, with symptoms lasting one to three days.
COVID-19 symptoms typically involve the respiratory system and vary widely in severity. Common symptoms include fever, cough, fatigue, sore throat, congestion, and changes in taste or smell. While gastrointestinal symptoms like nausea, vomiting, or diarrhea can occur with COVID-19, they are less common or primary than with norovirus. Symptoms usually appear 2 to 14 days after exposure and can last from days to several weeks, with some individuals experiencing prolonged symptoms.
Preventing Infection
Prevention strategies for norovirus and COVID-19 share common hygiene practices but also have distinct recommendations. Thorough handwashing with soap and water for at least 20 seconds is a highly effective measure against norovirus, particularly after using the toilet, changing diapers, or before preparing food. Alcohol-based hand sanitizers are less effective against norovirus compared to soap and water.
For norovirus, proper cleaning and disinfection of contaminated surfaces using bleach-based solutions is important. A solution of 5 to 25 tablespoons of household bleach (5-8%) per gallon of water can disinfect, ensuring the surface remains wet for at least five minutes. Safe food handling, avoiding food preparation when sick, and isolating infected individuals are other measures.
For COVID-19, vaccination is a primary preventive measure, significantly reducing the risk of severe illness, hospitalization, and death. Wearing well-fitting masks, especially in crowded or poorly ventilated indoor settings, helps reduce the spread of respiratory droplets. Improving indoor ventilation through open windows or air filtration systems helps disperse viral particles. Maintaining physical distance, particularly in crowded areas, can further reduce transmission risk.
When to Seek Medical Care
Most norovirus cases resolve on their own, but medical attention may be needed if signs of severe dehydration develop. These signs include decreased urination, dry mouth and throat, dizziness when standing up, extreme thirst, or unusual sleepiness or fussiness, especially in young children, older adults, or those with weakened immune systems. Persistent vomiting or diarrhea, high fever above 102°F (38.9°C), or severe abdominal pain warrant consulting a healthcare provider.
For COVID-19, emergency warning signs indicate immediate medical care. These include trouble breathing, persistent pain or pressure in the chest, new confusion, inability to wake or stay awake, or pale, gray, or blue-colored skin, lips, or nail beds. Worsening symptoms, particularly with underlying health conditions, should prompt a call to a healthcare provider. Individuals with mild symptoms not at high risk for severe illness can often manage their symptoms at home, similar to a common cold or flu.