These include Influenza A/Puerto Ri

These include Influenza A/Puerto Rico/8/34 (PR8), Influenza
A/WSN/33, and Influenza B/Lee/1940. Infection of mice with
the WSN and PR8 viral strains results in severe pneumonia
and, with sufficiently large viral inocula, in mortality in both
Balb/C and C57BL/6 strains. To generate murine-adapted
viral strains, investigators passaged isolates of human IAVs
in murine tissues (most commonly brain). Other viral strains
used that do not require viral adaptation include the 1918
H1N1 pandemic strain, the HPAI H5N1 strain, a few of the H7
subtype and low-pathogenic avian influenza viruses, and the
2009 H1N1 pandemic strains. Because these viral strains do
not need prior adaptation, they may be appropriate for studies
examining the efficacy of novel therapies when appropriate
safety precautions are taken.