#3: West Nile Virus
WNV is transmitted by mosquitoes, which pick it up from infected birds. Most cases go undetected as there are no symptoms at all. When symptoms do manifest, they can do so as the milder West Nile Fever (fever, fatigue, head and body aches), which generally doesn’t require treatment, or the more serious and far more rare West Nile Disease (encephalitis, meningitis, and other nervous-system diseases), which gets only supportive care but can require hospitalization.

Outbreaks can occur anywhere in warmer months, particularly near standing water, but are common in the temperate southern states. In these areas, use insect repellant and, when camping, mosquito netting. Avoid being outdoors when bugs are most apt to bite (e.g., dusk), and wear clothing that covers your arms and legs.

#4: Diarrheal Diseases
These are perhaps the most common travel diseases and can be bacterial (Salmonella), viral (norovirus), or parasitic (Giardia). Most cause self-limited illness, and treatment is primarily supportive. The best prevention is good hygiene: ensuring that your produce is thoroughly washed or peeled, that your meat is well cooked, and that your hands are washed regularly and vigorously. If you're traveling in the mountains, do not drink untreated spring water — often the breeding ground of the hardy Giardia parasite. Seek care immediately if diarrhea is persistent; bloody; and/or associated with severe vomiting, fever, or abdominal pain.

#5: Influenza
A respiratory illness and seasonal killer with many strains, influenza can be easily transmitted in confined spaces, such as a plane, making it a travel disease of sorts. Although it caused a scare in recent years, the H1N1 (swine flu) strain is usually milder than Influenza A but sometimes more lethal in the very young, the very old, and those with chronic conditions. The best prevention? An annual flu vaccination.

Also of interest: 5 travel dangers that can be fatal.