Japanese researchers say they have developed a way to observe how bird flu infections spread inside living mice.
Professor Yoshihiro Kawaoka and his team at the Institute of Medical Science, the University of Tokyo, created a microscopic imaging system enabling them to observe the viruses developing inside the lungs of mice.
Researchers infected mice with 2 different strains of influenza -- a mouse-adapted human strain of H1N1, and the highly pathogenic "bird flu" strain H5N1, which is known to cause serious symptoms in humans.
Images captured by the new system showed lung cells infected with H5N1 shining in fluorescent green inside networks of red blood vessels while damaged capillaries appeared to leak.
Images also showed neutrophil cells -- a type of white blood cell that plays an important role in immune systems -- gathering in blood vessels as the infection took hold.
Professor Kawaoka says the study offers insight into the physiological impact of these viruses which may lead to improved medical treatment.