Oh man, I could talk about this for awhile. It really depends on where parts in the US you’re from. Infectious diseases is so fun because the geographic and epidemiological aspects of life will change your differential. It’s pretty dope.
I love this question but there’s no easy way to talk about this without the post becoming a straight-up book chapter. I like that you brought up West Nile virus, because it’s definitely in the US and was traditionally an East Coast disease but has been on the West Coast since the early 2000s.
Since there are so many infectious diseases to talk about, let me do this instead:
5 overlooked infectious diseases in the US:
1. Powassan virus: carried by ticks, not just found in the US but also Russia, and the first case was discovered in Canada. This one is good to mention because cases are increasing in the US, especially Northeast and Great Lakes in the late spring, early summer, and mid-fall when ticks are most active.
2008-2017 Powassan virus reported by state
Source: https://www.cdc.gov/powassan/statistics.html
2. Bourbon virus: named after Bourbon County, Kansas where the first case was isolated. It’s carried by ticks and found in the same region and Heartland virus. You can read about it on the CDC website here: https://www.cdc.gov/ncezid/dvbd/bourbon/index.html
3. Heartland virus: 30 cases thus far documented, all in the Midwest and the South. Like many of the tick-borne viral diseases, sx are fevers, muscle and joint pain, low platelets. It’s not very specific in its symptoms.
States with reported cases as of 9/2018
Source:https://www.cdc.gov/heartland-virus/statistics/index.html
4. St Louis encephalitis: carried by mosquitos, spreading across the US. Sx can be as minimal as fever and headache, which then self-resolves or neuroinvasive disease including confusion, paralysis. Although the geographic range of the virus extends from Canada to Argentina, human cases have almost exclusively occurred in the United States.
Source: https://www.cdc.gov/sle/technical/epi.html
5. Hantavirus: carried by murine hosts (rats, etc) notably in the Southwest. Not all people get the very dramatic and often fatal hantavirus pulmonary syndrome.