As fears grow around the recent hantavirus outbreak linked to the cruise ship MV Hondius, many are asking the same question: when does a disease outbreak officially become a pandemic? 

According to the World Health Organization (WHO), a pandemic is defined as “the worldwide spread of a new disease.” But the label is not based only on death counts. The WHO looks at several key factors before considering an outbreak a pandemic-level threat. 

How WHO classifies a pandemic 

The WHO’s pandemic preparedness framework — originally designed for influenza outbreaks — focuses heavily on human-to-human transmission and global spread. 

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The progression broadly works like this: 

1. Phase 1-3: Early outbreak stage. At this stage, infections may jump from animals to humans, but transmission between people is either absent or limited. WHO says small clusters or isolated infections do not automatically indicate pandemic risk. 
2. Phase 4: Sustained human transmission. This is the critical warning stage. WHO considers it serious when a virus shows the ability to sustain “community-level outbreaks” through ongoing human-to-human spread. 
3. Phase 5: Spread across countries. The disease begins spreading between humans in multiple countries within a WHO region, signalling that a pandemic may be imminent. 
4. Phase 6: Pandemic. A pandemic is considered underway when there are community-level outbreaks in multiple countries across different WHO regions. 

Importantly, WHO experts have repeatedly said that the term “pandemic” refers more to geographic spread and sustained transmission, not necessarily how deadly a disease is. 

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Is the hantavirus outbreak at pandemic level? 

At present, the answer is no. Health officials and WHO experts say the current hantavirus outbreak does not meet the conditions associated with a pandemic. The biggest reason is transmission. 

Most hantaviruses spread to humans through contact with infected rodents, especially exposure to urine, droppings or saliva particles. Human-to-human transmission is considered extremely rare and is linked mainly to the Andes strain found in South America. 

WHO officials monitoring the MV Hondius outbreak have said there is currently no evidence of COVID-style widespread transmission. 

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That means the outbreak, while serious and deadly for some patients, has not shown the sustained community spread needed for pandemic classification. 

Hantavirus vs COVID-19: Why experts say they are different 

COVID-19 became a pandemic because it spread easily through respiratory droplets and aerosols, allowing sustained transmission across continents within weeks. WHO declared COVID-19 a pandemic on March 11, 2020. 

Hantavirus, by contrast, is far less transmissible between people, which sharply limits its ability to trigger worldwide outbreaks. 

Even though health agencies do not see a pandemic threat right now, experts say the hantavirus outbreak still deserves attention because: 

• It has a high fatality rate in severe cases 
• Symptoms can worsen rapidly 
• International travel can complicate tracing efforts 
• Rare human-to-human transmission has been documented in some strains. 

WHO has urged countries to continue surveillance, isolation, contact tracing and cross-border coordination.

Published on: May 8, 2026 3:24 PM IST