There are many broad, societal reasons for the expansion of dengue in the Americas. These include:

• Extensive vector infestations due to absent or ineffective vector control programs. There has been a general deterioration in vector control activities. In addition, some traditional control methods are ineffective against Aedes aegypti.
  
• Unreliable water supply systems produce the need to store water in containers, and thereby increase potential mosquito reproduction sites.
  Increased use of non-biodegradable containers, and poor solid-waste disposal, resulting in large numbers of containers that can collect water and create ideal sites for mosquito production.
  
• Increased air travel, which has made it possible for people to move the virus rapidly from one country to another. And
  
• Increased population density in expanding urban areas.