The researchers from United States and the Netherlands used ferrets in the study and found that the new H1N1 flu virus replicated more extensively in the respiratory tract, going to the lungs, but the seasonal flu virus stayed only in the animals’ nasal cavity. Unlike seasonal flu, the HINI virus went into the ferrets’ intestinal tract.

According to US researchers, such distinctions can make a difference in establishing appropriate public health responses as the pandemic continues around the world, which affected a million people in the United States alone.

Findings from the study demonstrate that, in ferrets, the novel 2009 H1N1 influenza virus leads to increased morbidity and increased respiratory disease when compared to contemporary seasonal human influenza viruses, said researcher Terrence M. Tumpey, a senior microbiologist in the influenza branch of the US Centers for Disease Control and Prevention in Atlanta.

Additionally, virus transmission was less effective in ferrets infected intranasally with novel 2009 H1N1 influenza virus, compared to those infected with contemporary seasonal human influenza viruses, he added.

Both the teams made different conclusion when they looked at how easily the new H1N1 virus can be transmitted.

The Dutch researchers found that H1N1 virus and the seasonal flu virus infection was equal in animals.

But US team found that the swine flu virus might not be transmitted as easily as the seasonal flu virus. The novel 2009 H1N1 influenza viruses exhibited less efficient respiratory droplet transmission in ferrets, in comparison to the high-transmissibility of a seasonal H1N1 virus, he said.

The researchers noted that ferrets are used to study influenza because the flu virus affects are similar in human.

One thing we know for sure about influenza viruses is that they are unpredictable, Tumpey added. The characteristics that the virus is displaying today might not hold true in the upcoming months.

He added that it is important to remember that this is a new influenza virus never seen in humans before April 2009.

The virus does not appear to be fully adapted to its new human host, Tumpey said. How the virus may adapt further as it circulates among people is not known. However, this uncertainty makes it imperative that the virus and the epidemiology of the outbreak be closely monitored.

Dr. Pascal James Imperato, dean of the School of Public Health at SUNY Downstate Medical Center in New York City, found the new research supported the information to what was already known.

In this study, it was found that the 2009 H1N1 virus was less efficiently transmitted by droplet infection in ferrets compared to the seasonal human H1N1 virus, Imperato said. This is a significant finding as it indicates that the 2009 swine flu virus might not be as easily transmitted between humans as its seasonal counterpart.

On the other hand, he added, the findings also collectively demonstrate that it has the potential to cause serious clinical illness that also results in gastrointestinal symptoms, which were, in fact, observed in a number of patients.