The Looming Threat of Dengue Fever in the U.S.

It's summertime, and one of the rites of the season is the onset of mosquito activity in many parts of the country. For most Americans, these pests are simply an annoyance, but in many parts of the world they can be deadly, and they could become more dangerous here too.  

A new report from the Natural Resources Defense Council, Fever Pitch, describes some of the factors that have contributed to the 30-fold increase in a mosquito-carried viral disease, dengue fever, over the last fifty years.

Two mosquito species that the new NRDC report maps in the US, Aedes aegypti and Aedes albopictus (also known as the Asian Tiger), have been known to carry the dengue fever infection. That doesn't mean they are all teeming with the virus naturally, but rather that they are able to contract the virus by biting someone sick with dengue and then transmit the virus to others. Just because the mosquitoes are in your state or county doesn't always mean that dengue fever disease outbreaks will occur, or that you'll get the disease - it simply means that your state or county may be vulnerable to an outbreak in the future. NRDC's report finds that more than 173 million Americans in at least 28 states live in counties where one or both of these mosquitoes have been found.

We would like to see more testing of mosquitoes in the US so we can know if, when, and where mosquitoes are carrying the dengue virus. When travelers infected with dengue fever "import" the virus back into the US, especially during the summer months when mosquitoes are active, it could increase the possibility of local transmission to other people.

Unless there's a large outbreak of the disease, you may not be able to find out how many cases of dengue fever are being reported in your state for months or years. Because the reporting system is so slow, and filled with holes, we'd like to see the system changed and updated. NRDC is advocating for dengue to become a nationally notifiable disease, with more rapid central reporting of suspected dengue fever cases, so individuals and scientists can get up-to-date information about the number of dengue cases in their state in a matter of weeks.

To help prevent an outbreak in your community, be sure to remove mosquito habitats around your home: empty any standing water from flower pots, buckets, or empty cans, and get rid of old tires or empty containers. Clean your pet water bowls daily, and watch out for clogged rain gutters: the mosquito vectors breed in standing water.  Cover outdoor cisterns if you have them, and ask your neighbors to do the same.

And since global warming may be affecting dengue, an effective way to reduce the likelihood of spread is to address climate change at its source by reducing global warming emissions. Call your Senator or Representative to ask them what they're doing to protect their constituents from dengue fever and other climate-change related health risks (which include increases in deadly heat waves, air pollution-related illnesses, and the frequency of extreme storms with flooding.)

Is NRDC saying that global warming is the main cause of the increase in dengue fever infections in recent years? Nobody knows precisely why dengue fever infections have been increasing, and there are likely multiple reasons. But global warming and its associated increasing temperatures, lengthening summers, and changing patterns of rainfall and droughts, are among the factors that can make it easier for dengue to spread. Other factors include uncontrolled, unplanned urbanization and population growth; rapid international travel and trade; and widespread poverty. All these factors can help dengue-carrying mosquitoes exist in closer proximity to people. Global warming may work in conjunction with these factors by helping the mosquito "vectors" live longer, in more, and in different, places. NRDC is advocating for more funding for local environmental monitoring and disease surveillance that will, in the future, make it easier to understand the relative importance of all the different factors that may be giving dengue fever such a strong foothold in the Americas.