HONG KONG, (Reuters) – A leading virologist has  described the new H1N1 influenza virus as “very unstable”,  meaning it could mix and swap genetic material when exposed to  other viruses.

The new virus, which has infected 5,251 people in 30  countries and killed 61, has displayed great efficiency in  spreading among people, said Guan Yi, a microbiologist with the  University of Hong Kong.

“This virus has been around only a few months, it is very  unstable … and we know that its presence is dramatically  increasing in human population, so the chance of it meeting  with H5N1 is actually increased,” Guan said in an interview on  Tuesday.

“Both H1N1 and H5N1 are unstable so the chances of them  exchanging genetic material are higher, whereas a stable  (seasonal flu) virus is less likely to take on genetic  material.”

While H1N1 appears to be mild so far with many infected  people recovering even without treatment, the H5N1 has a  mortality rate of between 60 to 70 percent.

Experts are fearful about the emergence of a hybrid which  combines the killing power of the H5N1 with the efficient  transmissibility of H1N1. H5N1 is believed to be endemic in  countries like China, Indonesia, Vietnam and Egypt.

Guan, an expert on both the H5N1 and SARS, has analysed the  genetic sequences of the new virus, which is a triple  reassortant containing genetic material from swine, human and  bird.