HGA is caused by bacteria (germs) that attack certain types of white blood cells called granulocytes. HGA was previously known as human granulocytic ehrlichiosis.
In the United States, HGA is most commonly found in the Northeast, mid-Atlantic and upper Midwest. In Massachusetts, the disease has been spreading and is now found throughout the state.
HGA is one of the diseases that can be spread by the bite of an infected black-legged (deer) tick. The longer a tick remains attached and feeding, the higher the likelihood that it may spread the bacteria. Black-legged ticks in Massachusetts can also carry the germs that cause Lyme disease and babesiosis. These ticks are capable of spreading more than one type of germ in a single bite.
HGA can occur during any time of year. The bacteria that cause HGA are spread by infected black-legged ticks. Young ticks (nymphs) are most active during the warm weather months between May and July. Adult ticks are most active during the fall and spring but will also be out searching for a host any time that winter temperatures are above freezing.
Symptoms of HGA usually begin to appear 7 to 14 days after being bitten by an infected tick.
Symptoms of HGA generally include fever, headache (that often doesn’t get better with over-the-counter medicine), chills, muscle ache, and fatigue. Less commonly, people may have abdominal pain, nausea, vomiting, diarrhea, cough and joint aches.
HGA can be treated with antibiotics. It is important to begin treatment early to prevent serious, potentially life-threatening complications
