The consultant peers at me over his half-moon specs like a mad professor eying a scientific curiosity: “And you took the antimalarial drugs as directed?” “I did,” I say. “I took Malarone, as advised by my GP for travel in Kenya.” He nods pensively and then continues writing in my notes, his ballpoint pen tapping noisily against the desk.

Not only did I take Malarone, the “Rolls-Royce” of anti-malaria pills — high-performing and staggeringly expensive — I also slept under a treated mosquito net, as did my four-year-old daughter, my travel companion.

Our room was sprayed by Fred, one of a team of staff that outnumbered the guests at the glamorous beachfront house in Lamu, an island off the East African coast. And every evening I doused myself in insect repellent, slapping it on with all the fervour of a WAG with a bottle of fake tan. As a result I was bitten only twice.

Before I booked the flight to Nairobi I balanced the risk of illness against the cost of the holiday. Europe is too expensive right now. Travelling farther afield meant more value for my pound, and a more exciting trip. My host in Lamu was an old friend, a charismatic adventurer who had grown up between Africa and London.

Through the day we feasted on fruits, fresh fish, lobster, crab, shrimps and salad. The island has no cars and my daughter, to her joy, didn’t need to wear shoes. We took dhow fishing boats past mangrove swamps to laze on empty beaches — empty except the wild baboon sitting on a nearby rock. And every night we toasted the sun as it set on the Indian Ocean.

Six weeks on and I am at the decidedly unglamorous Hospital for Tropical Diseases, in Central London. My symptom? A persistent headache. And I keep falling asleep. My GP has referred me “as a precaution”, and the nurse who checked me in refers me for a routine blood test, saying: “We always check for malaria. It’s not worth our reputation to miss a case.”

The waiting room is full. There are gap-year kids looking fashionably bedraggled and smart middle-aged couples seeking medical advice. Despite the spring sunshine, one man is wrapped in a wool jacket and is sweating profusely. An Australian woman is chatting to staff in a cheerful twang as she hands over a wad of medical notes as big as the telephone directory. Then I’m called.

“Well,” says the doctor, “thank goodness you came in. You have falciparum malaria.” I am stunned. I was bitten only twice. “Unfortunate,” the doctor concedes. But I have no fever, no chills. “Symptoms can be non-specific,” he explains, adding that he sees hundreds of patients with malaria a month. “You are in a small minority who present late, and with few symptoms. It’s a serious disease but it is treatable.”

As the parasites in my blood are resistant to Malarone, I will be given a course of quinine, the sideeffects of which include tinnitus, nausea, shakes and hypoglycaemia.

“It’s unlikely that your daughter has it,” he continues, “it’s rare with Malarone.” I discover later that I am the first person that the consultant has seen who caught malaria while on the drug, which explains his scrutiny of my case.

Of the four strains of human malaria — the others are vivax, ovale and malariae — falciparum is the most common (80 per cent of all cases) and the most dangerous. Every year 250 million people contract the disease, according to the World Health Organisation (WHO), and it kills an astonishing one million — including one child every 30 seconds.

Falciparum is also called “malignant” malaria and “cerebral malaria” because it can pass into the brain and put you in a coma. It can cause complications such as renal failure, liver damage and severe anaemia.

It is endemic in West Africa, but also on the Kenyan coast. I think back to mothers who criticised me for giving my daughter Malarone, suggesting homeopathic medicine instead. It was, I reflect, amazingly dangerous advice. In the UK there are 1,600 cases a year in travellers from abroad; between 10 and 12 die. Travellers such as me, going from malaria-free areas to a disease “hotspot”, such as the Kenyan coast, are especially vulnerable to the disease, according to the WHO.

Had I known these hard facts, my calculation between cost and illness might have been different. I would have gone, yes, but would I have taken my four-year-old? I am not alone, however, in choosing cost over risk. The Civil Aviation Authority recently reported that traffic between Heathrow and the eurozone had fallen by 8.7 per cent, while traffic to other destinations was up by 1.8 per cent.

Those travelling long-haul are, by definition, going to more exotic locations. Mexico has dropped off the list because of swine flu, but Africa, India, Thailand and Latin America are all popular — despite the risks of malaria, dengue fever, yellow fever and a host of other diseases.

“We have seen an increase in the numbers booking long-haul, for longer trips,” says a spokeswoman for Trailfinders, the travel agent. She adds that the company travel clinic, which dispenses vaccinations and antimalarials, has also noted an increase in requests for advice, “including information on areas with malaria, such as Africa”.

Controversially, Dr Ron Behrens, consultant in tropical and travel medicine at the Hospital for Tropical Diseases, does not always recommend antimalarials for India or South and Central America, where vivax malaria is present.

“The risk is low,” he says, “and adverse effects from the drugs is high. It is almost always ‘benign’ malaria — the relapsing form that rarely kills.” He adds, however: “Africa is where you find falciparum, life-threatening malaria. I don’t argue with anyone who refuses to take pills, but I think they are crazy.”

There is “good news” for me, however. My parasite count is low — under 0.01 per cent — “probably because the Malarone gave it a good beating”, the doctor explains.

I’m relieved, obviously, but given that my chances of getting malaria in the first place must have been about 1 per cent, I don’t feel like celebrating.

What the doctor says

Travellers must know their “ABCD “of malaria — acccording to Dr Ron Behrens, at the Hospital for Tropical Diseases.

A — Awareness of risk Get good, up-to-date information on the area you are visiting from your GP or a specialist centre, such as Trailfinders Travel Clinic.

B — Bite prevention Sleep under a net impregnated with insecticides and, if necessary, spray your room. From dusk to dawn apply long-lasting insect repellent and in the evening wear clothes that cover as much skin as possible.

C — Chemoprophylaxis (pills) Take antimalarials that are suitable for you and for the area that you are visiting as antimalarial drug resistance is a big problem. Finish the drugs prescribed by your doctor. Never buy antimalarial drugs over the internet, or from non- medical sources in the country that you visit.

D — (Rapid) Diagnosis It is vital to mention as soon as possible to your healthcare provider that you have been to a malaria area, or you can get sick and die because no one thinks of it. Malaria symptoms include high fever, chills, sweats, nausea and vomiting, headache and fatigue, but can also be non-specific, such as “feeling under the weather”. Depending on the strain, symptoms can appear from seven days to a year after exposure.

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