As global health officials continue monitoring outbreaks of infectious diseases, three viruses — norovirus, hantavirus and COVID-19 — are once again drawing public attention. While all three can make people seriously ill, they differ sharply in how they spread, the symptoms they cause, how deadly they are and whether vaccines exist. 

Here’s a closer look at how the viruses compare. 

What is norovirus? 

Norovirus is a highly contagious stomach virus often linked to cruise ships, schools, hospitals and contaminated food. It spreads rapidly through contaminated food, water, surfaces and close contact with infected people. 

The virus mainly attacks the digestive system and is often called the “winter vomiting bug.” 

Common symptoms 

• Vomiting 
• Diarrhoea 
• Stomach cramps 
• Nausea 
• Mild fever and body aches 

Symptoms usually appear within 12 to 48 hours and last for one to three days. 

Severity and deaths 

Norovirus is usually mild for healthy adults, but it can become dangerous for infants, elderly people and immunocompromised patients due to severe dehydration. Fatalities are relatively rare compared to other major viral diseases, though outbreaks can hospitalise thousands globally each year. 

Vaccine status 

There is currently no approved vaccine for norovirus, although several candidates are under development. 

What is hantavirus? 

Hantavirus is a rodent-borne virus that spreads mainly through exposure to infected rodent urine, saliva or droppings. Unlike COVID-19, widespread human-to-human transmission is uncommon, though limited transmission has been documented with certain strains such as the Andes virus. 

The virus can cause two severe illnesses: 

• Hantavirus Pulmonary Syndrome (HPS/HCPS) 
• Hemorrhagic Fever with Renal Syndrome (HFRS) 

Common symptoms 

Early symptoms include: 

• Fever 
• Muscle pain 
• Fatigue 
• Headache 
• Nausea and vomiting 

Hantavirus is far deadlier than norovirus and significantly more lethal than COVID-19 in severe forms.

Some hantavirus strains in the Americas can have fatality rates reaching up to 50%, while Asian and European strains generally show lower death rates. However, hantavirus infections remain relatively rare compared to COVID-19. 

Health experts say hantavirus is unlikely to become “the next COVID” because its transmission patterns are very different and sustained human-to-human spread remains rare.

Vaccine status 

There is currently no globally licensed vaccine or specific antiviral cure for hantavirus infections. Treatment mainly focuses on intensive supportive care. 

What is COVID-19? 

COVID-19, caused by the SARS‑CoV‑2 virus, became the world’s biggest pandemic in a century after emerging in late 2019. It spreads primarily through airborne respiratory droplets and particles. 

Common symptoms 

• Fever 
• Cough 
• Sore throat 
• Fatigue 
• Loss of taste or smell 
• Breathing difficulty in severe cases 

Some patients also develop long COVID, a condition where symptoms continue for months. 

Severity and deaths 

COVID-19 has caused more than 7.1 million reported deaths worldwide since 2019, though the actual toll is believed to be higher. 

Most infections are now mild due to widespread immunity from vaccination and prior infection, but older adults and people with chronic illnesses remain vulnerable to severe disease. 

Vaccine status 

COVID-19 differs sharply from norovirus and hantavirus because multiple vaccines are widely available globally. More than 13.6 billion vaccine doses had been administered worldwide by the end of 2024.

Published on: May 10, 2026 5:02 PM IST