While research continues to advance our understanding of bed bug biology and behavior and how to treat them properly, there are still many unanswered questions that puzzle numerous experts.
One topic that continues to challenge many of the top minds is why bed bugs infest certain cities and states worse than others? Knowing that bed bugs infest homes and travel readily from home to home you would expect high-density cities to have some of the largest problems due to population density. Everything seems to be consistent with this understanding when you see New York City, Philadelphia and San Francisco in the “most-infested cities” lists that are released by Orkin and Terminix each year. But why are Cincinnati, Dayton and Syracuse high on these lists as they aren’t nearly as population-dense as New York, Philly and San Fran?
It’s also understood that bed bugs reproduce and spread faster in warmer conditions. This would suggest that major metropolitan areas in the South should be “hotbeds” for bed bug activity. That being said, if you split the United States into five regions (figure 1, below), and organize the Terminix Top 15 cities from 2012 and 2013 and the same Top 20 from Orkin in 2013 into those regions, you see only 7 out of 40 entries for cities from the Southeast and South Central areas, and none of those cities are in either list’s Top 10. This glimpse into the data appears to suggest that northern cities may have more prevalent bed bug issues than cities in the South.
According to Gary Curl of Specialty Products Consultants, Mendham, N.J., bed bug services account for the following percentage of total 2013 revenue as reported by pest control companies in his annual survey:
- Northeast — 13.5 percent
- Midwest — 9.3 percent
- Southeast — 4.7 percent
- South Central — 4.2 percent
- West — 6.3 percent
This data suggests that bed bug treatments make up a more significant portion of pest control company business in the Northeast and Midwest compared to the South.
Using the same regional classification system, the Terminix and Orkin Top 15 and 20 cities were mapped. To balance the influence of each company (Terminix only lists 15 cities while Orkin lists 20), we analyzed Terminix’s Top 15 list from 2012 and 2013 and found that there were 20 cities in common between the two lists. The 20 cities from each company’s list were then placed in each region accordingly. Each time a city appeared on both lists (such as New York City), it was counted as two entries for a region and grouped accordingly:
- Northeast — 10
- Midwest — 16
- Southeast — 4
- South Central — 3
- West — 7
The mapping of the “top bed bug-infested cities” lists appears to demonstrate a similar trend compared with Curl’s revenue data. Taking the same list of cities from Orkin and Terminix, the top cities were then split into “North” and “South.” The Southeast and South Central areas were designated as South along with Western states New Mexico, Arizona, Nevada and cities in California south of Fresno.
In the North there were 31 cities. In the South, there were 9 cities. Looking at this data one would quickly think that there is a clear “northern bias” for bed bugs. However, one must take into consideration that using the above North/South split, there are more states in the North (33.5 states) than the South (14.5 states). Therefore, you would expect to see more bed bug-infested cities in the North. So maybe there is a slight “northern bias” but we decided to look a bit further.
Using the same classification system the Top 40 U.S. cities by population were mapped (according to the 2010 census and 2013 population estimates):
- Northeast — 6
- Midwest — 7
- Southeast — 5
- South Central — 7
- West — 15
The number of cities that fall into each group is dramatically different compared to Curl’s data and the classification of the top bed bug cities list. Furthermore, grouping the top 40 U.S. cities by population using the same North/South classification system mentioned previously reveals:
- North — 20 cities
- South — 20 cities
Comparing Gary Curl’s revenue data, Terminix and Orkin’s Top 15 and 20 most infested-cities lists, and U.S. census data, it suggests a clear bias by bed bugs for northern cities. Looking at Orkin and Terminix’s city lists there are three times more bed bug-infested cities in the North compared with the South. Compare this to the 50/50 North vs. South split found with the census data and a “northern bias” becomes more evident.
Why is This Happening?
The next step will be trying to determine why this northern bias may exist. There are many factors that could contribute to why a given city has a bed bug problem, including:
- High-rise buildings and population concentration definitely plays a role in the spread of bed bugs and it’s possible that more cities in the North have higher concentrations of people in small areas. Some southern cities have much more sprawl to their population where a given city may cover hundreds of square miles.
- Air conditioning in lower-socioeconomic communities may play a role in the population of bed bugs and their spread. In the South many affordable housing communities provide air-conditioned units due to the uncomfortable temperatures in the summer. In the North, many affordable housing communities are without air conditioning since heat waves and warmer conditions last a shorter time and many individuals can live comfortably without them. Past research has demonstrated that bed bugs can develop from an egg to an adult at 64oF in 60 days while the same process only takes 14 days at 82oF. Regulated, cool temperatures in air-conditioned units during the warmer months may slow reproductive rates as well as spread. In areas that lack air conditioning, bed bugs reproduce and spread more rapidly during warmer months when the temperature inside a home can exceed 85oF.
- Lastly, two bed bug species are known to infest homes in the United States: the common bed bug, Cimex lectularius, and the tropical bed bug, Cimex hemipterus. The tropical bed bug is known to be found more often in tropical regions and the common bed bug is the species thought to primarily infest the continental United States. The issue is that the two species look and behave similarly and it is nearly impossible to tell the difference without a microscope. The question becomes this: Does the common bed bug thrive in temperate cities/states? And is the southern U.S. (a transition temperature zone) an area between the common and tropical bed bugs where neither overly thrive? While the difference between the species doesn’t affect the control of the bug, it would be interesting to note which species is present inside an account to shed light on which is more prevalent and where.
Regardless of the reason or if this trend is observed 10 years from now, it is important to note that there are dramatic differences in the prevalence and spread of bed bugs from city to city and state to state. Understanding what influences the spread of bed bugs can help us learn how to slow the spread and perhaps create predictive models in regards to when and where a surge in bed bug populations will occur. Then again, maybe it’s just the last laugh of the confederacy…
Author’s note: I would like to thank Gary Curl of Specialty Products Consultants for permission to use data generated by his report, A Strategic Analysis of the U.S. Structural Pest Control Industry — 2013.
The author is director of innovation and technical content at BedBug Central, Lawrenceville, N.J.