in equine-1 or 2 serum can be used as diagnosis in horses. Other clinical findings may include a serous or light mucoid nasal discharge, epiphora, tender but rarely swollen submandibular lymph nodes, hyperemia of nasal and conjunctival mucosa, tachypnea, tachycardia, limb edema, muscle soreness and stiffness. Period of infectivity The length of time a horse can spread the virus after being infected. It is a very important concept, because horses can still infect other horses after they have gotten over their own illness. Viruses that are shed for long periods of time after a horse gets better are much harder to control. Horses tend to be most infectious (i.e. shedding the most virus) in the first 24–48 hours after they develop a fever, but they can shed the virus for up to 7–10 days after their signs of illness disappear. See also Horse flu Canine influenza References H3N8 1889–1890 flu pandemic