More than 320,000 mammalian viruses lurk; evolution of echolocation in bats and dolphins; accumulation of mutations in drug-resistant tuberculosis; senior researchers reluctant to retire
The creation of H5N1 bird flu strains that are transmissible between mammals has thrown the scientific community into a heated debate about whether such research should be allowed and how it should be regulated.
The bird flu virus infected several people who were also sick with seasonal flu, risking a genetic mixing of the two that could result in a greater threat.