AS an infectious diseases specialist, I travel to Johannesburg, South Africa, and Lilongwe, Malawi, four times a year for various projects related to my work with the human immunodeficiency virus or, as we all know it, H.I.V.

I also go to Ireland several times a year to forge collaborative projects between hospitals in Dublin and Lilongwe and to Trinidad/Tobago to help with their H.I.V. program. Then, of course, there are all the meetings I must attend both domestically and internationally. With all this travel, I've been anointed a "platinum" flier with several airlines.

I have been in the H.I.V. "business" since the beginning of the epidemic back in the early 1980s. Though there has been significant progress in treating and preventing H.I.V. during the last two decades, I find that I can still get overwhelmed. Besides family and friends, what keeps me going is exercise.

In the beginning, we didn't know what to call this disease. All we knew was that everyone with a certain set of symptoms wound up dying. It was frustrating and heartbreaking. To help clear my head, I started swimming. And then I started competing. For a short time, my biggest worry was the quality of my stroke. It was great distraction from the misery of dealing with patients I couldn't help.

To this day, every place I go I find the time to exercise. It's a wonderful way to see the country and to get that endorphin rush that makes a bad day a little more tolerable. For me, running through dusty fields of Malawi and hearing the Islamic call to prayer is mesmerizing. And I can't help but smile, when I'm running through a village and these gorgeous little African children start running with me yelling, "azungu," which can mean stranger, foreigner or white guy - all of which are true.

My colleagues and friends still have a tough time believing I spend a short layover in London doing laps in a pool. Or that I walk through German customs wearing my ratty running shorts. My daughters tell me I should get rid of them. Despite their embarrassment, I won't. The shorts are too comfortable.

The ultimate eyebrow raiser is on the South African Airways flight back from Johannesburg to the United States. This endless trip is enough to drive anyone crazy. My solution is to go into the restroom halfway through the flight and change into workout clothes. I then do a full hour of calisthenics, crunches, push-ups and lunges in the aisle of the plane. I'll ask the stewards for a lot of those steamy washcloths, and then retreat to the restroom for a sponge bath. I'll sleep like a baby for the rest of the flight.

I love to celebrate the successes that we have had in treating and preventing H.I.V. But we have so much more work to do. Despite our best efforts, it remains hard not to focus on the fact that H.I.V. is diagnosed in about 3,500 pregnant women in Lilongwe every year or the countless e-mails notifying me about the death of an infant.

But I've not given up. I will keep working to fight this disease. And I will keep running and swimming to help me, for just a few hours, escape from it.

*By Charles van der Horst, M.D., as told to Joan Raymond.