Lyme disease is caused by bacteria called Borrelia burgdorferi. These bacteria are transmitted from the bite of an infected nymph or adult black-legged deer tick:





Bites from other ticks, like dog ticks, wood ticks, and lone star ticks also transmit infection to humans, though Lyme disease is acquired only after the bite of an infected deer tick.  (More pictures of all these ticks are here (from the Lyme Disease Association).  Note that dog ticks — which are very common — are black.

Michael Specter explains the diagnostic criteria for making a diagnosis of Lyme disease in an excellent article in The New Yorker this week:

The Centers for Disease Control and Prevention has established highly specific criteria for the diagnosis of Lyme disease: an acknowledged tick bite, the appearance of a bull’s-eye rash, and, for those who don’t live in a region where Lyme is common, laboratory evidence of infection. Most people who fit the profile respond well to antibiotics, even months or years after the initial infection. Many Lyme specialists, however, believe that short-term antibiotic therapy may suppress symptoms but rarely cures the disease.


And it is here — where the science is unclear and frustrations run high — that the controversy about the treatment of Lyme disease begins.  First described in the medical literature in 1977 after an outbreak of infection in Lyme, Connecticut, the number of cases of Lyme disease rises every year as the geographical distribution of infected ticks widens:

Those facts are undisputed. But nearly everything else about Lyme disease—the symptoms, the diagnosis, the prevalence, the behavior of the borrelia spirochete after it infects the body, and the correct approach to treatment—is contested bitterly and publicly. Even the definition of Lyme disease, and the terminology used to describe it, has fuelled years of acrimonious debate. The conventional medical assessment is straightforward: in most cases, the tick bite causes a skin rash, called erythema migrans, which is easily identified by its bull’s-eye. If left untreated, the bacteria can spread to muscles, joints, the heart, and even the brain. Public-health officials say that a few weeks of antibiotic treatment will almost always wipe out the infection, and that relapses are rare. In this view, put forth in guidelines issued by the Infectious Diseases Society of America, Lyme is normally easy to treat and easy to cure.

For many people, though, the clinical situation is far more complicated.


Typical symptoms are not specific:  fever, headache, muscle aches, and fatigue.  The rash that can accompany a tick bite — erythema migrans or bullseye rash — is not present in all cases. If the diagnosis is made at this early stage, treatment with antibiotics (amoxicillin or cefuroxime under eight years old and doxycycline for those who are older) for 2-4 weeks is usually curative.  If this early stage of Lyme disease is not identified and treated, the bacteria can spread to the joints (arthritis), the nervous system (meningitis, bell’s palsy), heart (arrhythmias), and cause severe symptoms of debilitating and chronic fatigue and muscle pain.  In people with these symptoms, treatment options and recovery without residual health problems are variable, less than certain, and frequently a simple  matter of opinion.  This can be frustrating for people who suffer as well as doctors who treat them:

Most troubling, some patients who are treated continue to suffer from a variety of symptoms long after their therapy has ended. Nobody really knows why they fail to get better. Infectious-disease experts refer to the phenomenon, which can affect up to twenty per cent of patients, as Post-Treatment Lyme Disease Syndrome. Researchers have attempted to resolve the mystery in experiments with monkeys, mice, and dogs; human studies are also under way. As the number of infections grows, so does the number of people struggling to figure out what is wrong with them.

Specter goes on to identify the sides that make up the “Lyme War” and what it may take to finally answer the most pressing questions about Lyme disease:  patience and sound science.

Lyme disease is transmitted to humans only from an infected black-legged deer tick.  The tick needs to be attached and feeding for more than 36 hours for transmission to occur.  The longer the feeding goes, the bigger the engorged tick becomes.  The CDC provides advice for preventing deer tick bites and guidelines on the correct method of removing feeding ticks:


While it is a good idea to take preventive measures against ticks year-round, be extra vigilant in warmer months (April-September) when ticks are most active.

Avoid Direct Contact with Ticks

  • Avoid wooded and bushy areas with high grass and leaf litter.
  • Walk in the center of trails.

Repel Ticks with DEET or Permethrin

  • Use repellents that contain 20% or more DEET (N, N-diethyl-m-toluamide) on the exposed skin for protection that lasts up to several hours. Always follow product instructions. Parents should apply this product to their children, avoiding hands, eyes, and mouth.
  • Use products that contain permethrin on clothing. Treat clothing and gear, such as boots, pants, socks and tents. It remains protective through several washings. Pre-treated clothing is available and remains protective for up to 70 washings.

Find and Remove Ticks from Your Body

  • Bathe or shower as soon as possible after coming indoors (preferably within two hours) to wash off and more easily find ticks that are crawling on you.
  • Conduct a full-body tick check using a hand-held or full-length mirror to view all parts of your body upon return from tick-infested areas. Parents should check their children for ticks under the arms, in and around the ears, inside the belly button, behind the knees, between the legs, around the waist, and especially in their hair.
  • Examine gear and pets. Ticks can ride into the home on clothing and pets, then attach to a person later, so carefully examine pets, coats, and day packs. Tumble clothes in a dryer on high heat for an hour to kill remaining ticks.


More about Lyme disease from the CDC here.