Doctors 'in the field' are faced with patients turning up day and night at their clinics after having travelled from remote areas.
Patients travel for up to 250 miles to get to the centre, often bringing several relatives on what can be a two-day trek to reach help. Dr Harry said: "We were working 24/7. The doctors are facing an enormous challenge.
"For me, it was very different from working in Atlanta, America, where I had the support of 300 to 500 doctors each and every day. In the field, you were the healthcare worker, the laboratory worker - you were everything." He added: "There is a paucity of human resources, there is a shortage of doctors and nurses who can deal with malaria."
'Life or death' Medics are unlikely to have the opportunity to carry out a follow-up checks on patients, so they must make instant decisions about what they are suffering from and what treatment they need.
The pressure to treat patients quickly, plus a shortage of laboratory facilities means doctors are unable to send of blood samples for tests. This can mean patients are given anti-malarial medication if they have symptoms such as fever, even if they don't have malaria - adding to the growing problem of resistance to drugs.
"When that doctor is facing a patient, there is no room for a second chance. It's a life or death situation. They must try to decide what's the best option for that person in the field, at 2am."
While in Somalia, he carried out a study which showed using artemisinin drugs, derived from the Chinese plant Artemisia annua in combination with other drugs - known as ACT - was the most effective treatment for malaria.
Overdoses One 23-year-old woman came to the clinic after trying to treat her malaria with drugs that she bought herself. She tried chloroquin first, then Fansidar. It is common for people to self-medicate because health professionals are hard to reach.
Many areas have high levels of chloroquin resistance, so the drug does not work. but people often take high doses, thinking the more they take the more effective it will be. Fansidar can be effective, but there resistance to that drug is also growing. The woman was pregnant, but lost her baby. Doctors then treated her with ACT.
She made a full recovery. Dr Harry said it was crucial that effective, fast-acting drugs were available to doctors. Dr Harry said: "In the frontline, if you are the only doctor and you're seeing 20 to 30 patients with malaria. If you had a couple of bottles on the shelf, the choice is clear. You would choose ACT."