Dengue fever spreads north

The agonizing and sometimes fatal tropical disease is much more prevalent than previously thought
Edgard Garrido / Reuters

When Alec Falkenham got a rash on his back, he thought nothing of it. The 26-year-old from Halifax was vacationing last winter in Puerto Morelos, a small fishing village lined with palm trees a 45-minute drive south of Cancún, Mexico. “I figured it was because of a sea anemone,” he says. But when he got home, his bones began throbbing. “It’s the worst pain I’ve ever felt in my life. It’s like someone is squeezing your muscles and bones, just compressing them,” says Falkenham, who works as a doctoral student in pathology at Dalhousie University. He was eventually diagnosed with dengue fever, a mosquito-borne, potentially lethal virus. Falkenham would go to the emergency ward three more times that week, and spent the next week on painkillers, the only way to dull the agony. “It was two weeks of solid pain,” he says, “every day and every hour.”

Otherwise known as breakbone fever for the agony it causes, the full impact of the tropical disease is only now being appreciated. Earlier this year, a study led by Oxford University researchers estimated that more than 390 million people are infected annually, nearly quadrupling previous World Health Organization estimates. At least half a million are hospitalized with the most dangerous form of the infection that can include internal bleeding and fluid accumulation, and which kills approximately 2.5 per cent of those affected. The spread of the dengue virus is phenomenal. This year in Singapore, five died and more than 15,850 have been infected. In Thailand, there have been 94 deaths and 100,000 infections. Honduras declared a state of emergency in July after an outbreak killed 16 people and infected more than 12,000. Costa Rica was forced to do the same. And dengue is moving north. Last year, Europe saw a sustained outbreak for the first time in nine decades. Eight cases were recently reported in Florida. “Dengue appears to be reclaiming territory,” says Brian Ward, an associate professor researching zoonotic diseases (those that can transfer from animals to humans) at McGill University. “You have very large populations now living in dengue areas, and you have huge numbers of people moving between them.”

There’s no specific treatment for dengue, and the race is on to create a vaccine, predicted to be the next blockbuster addition to the $27-billion global vaccine market. It’s estimated a dengue vaccine could earn upward of $2 billion a year in sales. “For many years, large vaccine manufacturers decided there wasn’t a market for dengue vaccine. They couldn’t make a commercially viable product,” says Cameron Simmons, a professor of infectious diseases at Oxford University. “But, as some of these countries have transitioned from developing low-income countries to middle-income countries, a commercial market [has developed],” says Simmons, speaking from his lab in Ho Chi Minh City, Vietnam. Still, he adds that “for any new drug or vaccine, the road is a long one.”

At present, Sanofi Pasteur, France’s largest drug maker, is closest to finding a way to fight dengue. After decades of development, it hopes to have a vaccine to market in 2015. However, a clinical trial last year yielded disappointing results: The vaccine proved just 30 per cent effective, while one of the virus’s four strains was completely immune. Despite the setback, Sanofi is beginning production, predicting that the next round of trials will be more successful. “We are taking steps to be on time to deliver the first doses in 2015,” says Melanie Saville, chief medical officer of the dengue vaccine at Sanofi Pasteur. “We are confident in our ability to provide the first vaccine to protect against dengue.”

The demand is urgent, in large part because of dengue’s staggering economic cost. Deutsche Bank estimated dengue cost Latin America $2.1 billion in lost productivity between 2000 and 2007. “The problem with dengue is the sheer scale of the disease burden; it’s a very large number of people who develop this week-long, severe viral infection,” says Simmons. “That has an economic impact in households where health care is one of the biggest costs, and has health care implications for those countries.”

Canadians are safe from dengue—save for those who travel to tropical areas—because the disease has not spread this far north. As for Falkenham, the memory of his ordeal is hard to shake. “I live in fear of being exposed again, every time I even think of travelling anywhere.”