(CBS News) The Centers for Disease Control and Prevention says 2012 has been the worst year for the West Nile virus since 2003.
There have been nearly 2,000 cases of the disease so far this year, and 87 Americans have died.
The virus has been reported in 48 states this year, with almost 45 percent of cases in Texas. Another quarter of all cases have been reported from South Dakota, Mississippi, Oklahoma, Louisiana and Michigan.
Also, a Hanta-virus outbreak has killed three visitors to Yosemite National Park.
There was a case of bubonic plague last week in Colorado, while a big jump in the tick population could mean an upsurge in Lyme disease.
Dr. William Shaffner, past president of the National Foundation for Infectious Diseases, said the recent up-tick of infectious diseases is due, in part, to climate.
"We've had a very, very warm winter and summer, and the drought has got something to do with it also, Dr. Shaffner said on "CBS This Morning."
Of West Nile, he said, "You would think in a drought there wouldn't be many mosquitoes because mosquitoes transmit that infection to us. But it turns out in those few standing water sources, that's where mosquitoes breed, the birds comes down to feed there, the mosquitoes bite the birds, pick up the infection and then sometimes transmit it to us.
"The West Nile virus can cause an illness with fever, but particularly among older people, people older than age 50, it can cause encephalitis and then sometimes prolong systems after people recover."
The symptoms, he said, "look a little bit like the flu. Most people who get infected don't become ill. If you become ill you have this minor flu-like illness. But a few people get the serious nervous system complications."
The source of infection or Hanta virus, Dr. Shaffner said, are deer and mice. "They are looking for food and water and so their droppings are inhaled sometimes by us and then we get sick."
Symptoms: "Initially you get fever, feeling poorly, and then you can a pneumonia-like illness that can be very severe and also kidney failure."
"Is this something we have to start living with?" asked Charlie Rose.
"We have to live with it, because we go out into the wild and we encounter these infections that are in the animal world, in the wild, and we're at risk of getting them," Dr. Shaffner said.