WE learned lots about equine influenza this week. We learned that it is a respiratory infection that affects horses in much the same way as flu affects humans, for example. We learned that symptoms include a high fever, nasal discharge and coughing. We learned that, while symptoms in vaccinated horses are usually mild, it is highly contagious, and horses can remain infectious for about a week. And we learned that, while the disease is rarely fatal, performance can be affected for days or weeks, and that some horses can develop secondary bacterial infections.