My patient went to a local emergency room recently feeling unusually tired and feverish. There was no cough, congestion, shortness of breath, or diarrhea. He was given a test for COVID-19 and sent to a designated area for observation until his test result returned.

The test was negative and he was sent home to rest, drink plenty of fluids, and take Tylenol for what was either COVID-19 with a false negative test or a different viral illness.

The following day, his symptoms persisted, and his fever rose to 103 degrees, so he returned to the emergency room. This time, he had blood tests that revealed his platelet count (the cells that help with blood clotting) to be slightly low, and liver tests to be elevated, suggesting inflammation. His heart, lung, and abdominal examinations were normal, and imaging tests of the chest and abdomen were ordered. He was once again told he had a viral illness. If his X-rays were normal, the plan was to send him back home to rest and recover.

An astute intern was assigned to the case, and asked whether she could review his record and repeat his physical examination. When she opened up the patient’s gown to expose his back fully for her lung exam, she noticed an oblong, red rash with a tiny puncture mark in the middle. Suddenly, everything began to make sense.


My patient was not aware he had a rash, because it did not hurt or itch, and it was in an area he couldn’t see. When the intern questioned him further, he said he had been working outside near some tall grass over the last few days, a high-risk spot for tick bites.

He was admitted to the hospital and treated with antibiotics for suspected tick-borne illness, and his blood test confirmed babesiosis. He may also have Lyme disease, which occurs in 20% to 25% of babesiosis patients, and testing for this is in progress.

Babesiosis is a parasitic disease that is transmitted to humans through a tick bite. It occurs in the warmer months, and is common in the Northeastern and Midwestern states. The symptoms are similar to those of malaria, with fever, fatigue, and low blood counts, and liver and spleen enlargement. Fortunately, it responds to treatment with antibiotics.

This is a cautionary tale for doctors and patients alike. We are all potentially vulnerable to cognitive bias — meaning we favor certain answers that come to mind based on recent experience.

With COVID-19 being prevalent in clinics and hospitals, as well as dominating the news, it is bound to be our first thought when someone is ill with fever. We become “biased” in favor of the diagnosis that we see and hear about most each day. If we don’t consciously remind ourselves of this, it may distract us from giving proper attention to other diagnostic possibilities.

But my patient was persistent, and his intern was thorough, so he was properly diagnosed and is recovering. Whenever you are given a diagnosis, it is important to ask, “Is there anything else it could be?” While COVID-19 is still a serious threat, tick-borne diseases are another summer menace to be on the lookout for.

Jeffrey Millstein is a primary care physician and medical director for patient experience-regional practices at Penn Medicine.