In 1918 and 1919, the Spanish Influenza caused the death of at least 50 million people, and over 500 million people – about a third of the world’s population at that time – were infected with the Spanish influenza virus. Since there was no vaccine for the flu, people were forced to limit public gatherings and even turned to complete isolation or quarantine to prevent any further spreading of the flu. In 1935, Sir Frank Macfarlane Burnet was the first person to isolate the influenza virus. Three years later, scientists Jonas Salk, MD, and Thomas Francis Jr., MD, developed the first flu vaccine with the help of fertilized chicken eggs. Since then, another type of flu vaccine has been developed using mammalian cells instead of fertilized chicken eggs.
Mice and guinea pigs are also important animal models for understanding and treating the influenza virus. While these two animals do not exhibit the same symptoms of the flu as humans – and ferrets! – do, they present other advantages. Mouse models are small and easy to handle, making them useful in pre- clinical studies of influenza therapies. More recently, researchers have identified immune response mechanisms to influenza that are similar in mice and humans, opening the door to new, more effective treatments for the flu. Guinea pigs are smaller than ferrets, which means a greater number of guinea pigs can be placed in environmentally controlled spaces. As a result, guinea pigs have proven useful in influenza transmission studies.
Though this year’s flu shot may be a mismatch, the Centers for Disease Control and Prevention still recommend that everyone six months and older become vaccinated because the flu shot still provides some coverage, attenuates symptoms, and reduces the risk of transmission to other people.
Thanks once again to animal models (especially the ferret!), for their help in the discovery of yet another lifesaving vaccine.
By Nelia Dashiell