The number of Lyme disease cases diagnosed in the US every year is around 300,000, according to new figures released by the Centers for Disease Control and Prevention (CDC). This number is about 10 times higher than the number officially reported.

CDC officials presented their new preliminary estimates in Boston on Sunday at the 2013 International Conference on Lyme Borreliosis and Other Tick-Borne Diseases.

Lyme disease is the most commonly reported tick-borne illness in the US, where every year the CDC receives reports on 30,000 cases. The disease is transmitted to humans through the bite of ticks infected with the bacterium Borrelia burgdorferi.

The Lyme disease bacterium has a quirky feature for survival. It can exist without iron, which most other living organisms require to make proteins and enzymes. Instead of iron, B. burgdorferi uses manganese, thus eluding immune system defences that destroy pathogens by starving them of iron.

Symptoms of Lyme disease can feel like flu and include fever, fatigue, and headache, except these are also accompanied by a skin rash called erythema migrans. If untreated the infection can spread to joints, the nervous system and the heart.

Most cases of the disease that are reported to the CDC via national surveillance show the most affected states are in the Northeast and upper Midwest, with 96% of reports being made in 13 states.

The new estimates, which arise from three ongoing CDC studies, suggest that the total number of Americans diagnosed with Lyme disease is about ten times higher than the yearly reported number.

This agrees with studies reported in the 1990s that showed the actual number of Lyme diseases cases in the US was likely to be three to twelve times higher than reported.

Each of the three ongoing studies is using a different method to estimate the number of diagnosed cases.

  • One is using six years of information from medical insurance claims covering 22 million people;
  • Another is surveying clinical laboratories;
  • The third is doing a survey of the general public.

Paul Mead, CDC’s chief of epidemiology and surveillance for Lyme disease, says:

We know that routine surveillance only gives us part of the picture, and that the true number of illnesses is much greater.

This new preliminary estimate confirms that Lyme disease is a tremendous public health problem in the United States, and clearly highlights the urgent need for prevention.”

The studies will continue to analyze and refine the data so as to help health officials get a better picture of how Lyme disease is affecting the American population. The final estimates will be published when the studies complete.

In the meantime, CDC and other agencies are investigating and coming up with new ways to kill ticks and prevent people getting infected with Lyme disease.

Lyle Petersen, director of the CDC’s department on vector-borne diseases, says there is a need to improve on current methods that people use to prevent tick bites, like using repellents and checking for ticks:

“Although these measures are effective, they aren’t fail-proof and people don’t always use them. We need to move to a broader approach to tick reduction, involving entire communities, to combat this public health problem.”

A community approach would address the many ways humans come into contact with the Lyme disease bacteria, and the various means by which they spread.

Understanding how rodents carry the bacteria, how deer are important for the tick’s life cycle, and how deer, rodents, ticks and humans interact, plus suburban planning, will be important issues to address in such an approach, says the CDC.

You can help prevent Lyme disease and other tickborne illnesses by following these steps recommended by the CDC:

  • Check for ticks every day (on you, your pet, and in your yard).
  • Wear repellent (the CDC recommends DEET or permethrin).
  • Bathe or shower soon after being outdoors (preferably within two hours) to wash off and more easily find ticks that are crawling on you.
  • If you have been in a tick-infested area, carry out a full body check. Use a mirror to view all parts of your body.
  • Parents should check their children’s hair, under their arms, in and around the ears, the belly button, between the legs, around the waist, and behind the knees.
  • Ticks can hitch a ride on clothing and pets, so check them thoroughly. Tumble clothes on a high heat for an hour to kill any ticks you may have missed.
  • See a doctor if you get a fever or rash.

For more information visit the CDC’s web hub on Lyme disease.

Written by Catharine Paddock PhD