Megacity

(noun) 1: megalopolis 2: a city together with its suburbs or recognized metropolitan area with a total population in excess of 10 million people

Regardless of the primary destination, most people must at least pass through a megacity during their travels.

There are several health threats associated with congested, highly populated areas in addition to traffic accidents and infectious disease. The two most likely to impact non-residents are air pollution and crime.

Air Pollution

Air pollution can be a problem in any large city, but is more severe in the developing world. Between them China and India can claim sixteen out of the twenty most polluted cities in the world. Travelers with current problems with, or even a remote history of, asthma or other pulmonary conditions should have medication available.

Crime

Wherever you travel crime is a possibility. Large cities and developing countries are generally areas of higher risk. The World Health Organization suggests some precautions that may reduce your risk:

• Be alert to the possibility of muggings during the day as well as at night.
• Carry your passport and money in a hidden pouch or belt. Do not carry large amounts of cash.
• Keep jewelry, cameras and other items of value out of sight.
• Avoid isolated beaches and other remote areas.
• Avoid overcrowded trains, buses and minibus taxis.
• Use taxis from authorized ranks only or have a reputable hotel call one for you.
• Avoid driving at night and never travel alone.
• Keep car doors locked and windows shut.
• Be particularly alert when waiting at traffic lights.
• Park in well-lit areas.
• Employ the services of a local guide/interpreter or local driver when traveling to remote areas.
• Check with the Department of State for travel alerts or warnings for your destination before departure.