THE INFECTIONS. REHEMA ELLIS REPORTS ON HOW CITIES ARE TRYING TO KEEP PEOPLE SAFE. >> Reporter: AS NEW YORK SPRAYS FOR MOSQUITOS CARRYING DANGEROUS VIRUSES, EEE, CONCERN IS SPREADING NATIONWIDE. CASES POPPING UP IN MASSACHUSETTS, VERMONT, NEW JERSEY, WISCONSIN AND TONIGHT NEW HAMPSHIRE. NEW HAMPSHIRE HEALTH OFFICIALS SAY ONE ADULT RESIDENT DIED OF EEE AFTER BEING HOSPITALIZED FOR SEVERE NERVOUS SYSTEM DISEASE. IT IS NEW HAMPSHIRE'S FIRST HUMAN CASE OF THE VIRUS IN A DECADE. THE WEST NILE VIRUS IS A THREAT, TOO. 33 STATES HAVE REPORTED 289 CASES OF WEST NILE. >> THIS IS WORRISOME AND DISCOURAGING. >> Reporter: EPIDEMIOLOGIST AND INFECTIOUS DISEASE SPECIALIST DR. RICHARD ELLISON SAYS EEE VIRUS IS ESPECIALLY TROUBLING. >> WE HAVE 30% TO 40% OF THE PATIENTS WHO GET THIS AND BECOME SICK WITH IT WILL DIE FROM IT. >> Reporter: IS THERE ANY AGE GROUP THAT'S PARTICULARLY VULNERABLE TO THESE VIRUSES? >> THE VERY YOUNG AND THE VERY OLD ARE THE ONES WHO HAVE THE WORST OUTCOME. >> Reporter: OFFICIALS NATIONWIDE ARE TAKING ACTION, SPRAYING, TESTING TO IDENTIFY MOSQUITO-BREEDING AREAS. >> I'M GLAD THAT THEY'RE DOING SOMETHING PROACTIVE ABOUT IT. >> Reporter: SAFETY PRECAUTIONS INCLUDE WEARING LONG SLEEVES AND PANTS, USING INSECT REPELLENT AND GETTING RID OF STANDING WATER. TAKE EXTRA CARE DURING DUSK AND DAWN, OFFICIALS SAY. THAT'S WHEN