Bird Flu Not Spread Easily Among Humans / Virus Tends Not to Be Coughed or Sneezed into the Air, Studies Say

Why doesn’t bird flu spread easily between people? Scientists think they have found a reason.

The virus prefers to infect cells in the lung instead of such areas as the nose and windpipe, so it’s not easily coughed or sneezed out into the air, new research says.

But that behavior could change if the virus mutates. Experts say the new research does not indicate how likely the virus is to change genetically and unleash a worldwide outbreak of lethal flu. But the work suggests one of the signs to watch for in new virus samples to help gauge the danger to humans.

The work, reported in today’s issue of the journal Nature, comes from University of Wisconsin-Madison virologist Yoshihiro Kawaoka with colleagues in Japan. Similar results, from the Erasmus Medical Center in Rotterdam, the Netherlands, will be published online today by the journal Science.

More than 180 people are known to have been infected with the bird-flu virus H5N1. Virtually all are believed to have caught it from infected poultry. But scientists have long warned that the virus could transform itself into a version that spreads easily from person to person. That germ could touch off a pandemic.

Ordinary flu viruses spread when an infected person coughs or sneezes, blasting out tiny droplets carrying the germ. For that to happen, the virus has to be perched in the right places to be ejected by a cough or sneeze.

The new work suggests that H5N1 infects humans too low in the respiratory tract for that to occur.

Both research teams used human tissue removed from various parts of the respiratory tract – the region from the nose to the lung – to study where virus infec tion occurs.