A 68-year-old gardener presents to the emergency department with a 3-day history of fever, headache, myalgias, and weakness. He is awake but is confused and oriented only to person. Muscle strength is markedly diminished in the lower extremities and somewhat reduced in the upper extremities. Deep tendon reflexes are absent throughout. Acute serum and CSF samples revealed elevated levels of IgM antibodies to West Nile virus.What is the most common reservoir of the causative agent?

Wild birds

The main mode of WNV transmission is via various species of mosquitoes which are the prime vector, with **** birds ***** being the most commonly infected animal and serving as the prime reservoir host - especially passerines which are of the largest order (Passeriformes) of birds. WNV has been found in various species of ticks, but current research suggests they are not important vectors of the virus. WNV also infects various mammal species including humans and has been identified in reptilian species, including alligators and crocodiles, and also in amphibians. Not all animal species which are susceptible to WNV infection humans included, and not all bird species develop sufficient viral levels to transmit the disease to noninfected mosquitoes, and are thus not considered major factors in WNV transmission.[