Studies into the burden of dengue have primarily focused on the costs borne by patients and healthcare systems in endemic countries. But with today’s world more connected than ever, the burden of dengue is now being felt right across the globe. We spoke with Professor Yesim Tozan, lead author of ‘A Prospective Study on the Impact and Out-of-Pocket Costs of Dengue Illness in International Travellers’ to learn more.

“More people from countries not affected by dengue are travelling to endemic countries,” says the Professor. “If they contract the disease, it can have a significant impact, both during their travels and once they’ve returned home. We need to start thinking about all populations – not just people living in endemic countries – when it comes to dengue treatment, prevention and control.”

How travellers are affected by dengue

Professor Tozan’s research was a spinoff of the DengueTools project, a European-backed initiative hosted at Sweden’s Umeå University, investigating how to prevent the spread of dengue through better diagnosis, prevention and prediction. The project had three core areas of study, one of which explored how dengue is moving across the globe.

“After DengueTools, leveraging the partnerships we’d built to understand how international travellers were affected by dengue was a natural next step,” says Professor Tozan. “We reached out to travel and tropical medicine clinics in eight countries to learn about the burden of dengue on travellers returning home with a confirmed diagnosis.”

The study explored costs incurred by 90 travellers returning to their home countries of Australia, Austria, Germany, Israel, Italy, the Netherlands, Switzerland and the US. Two-thirds of the travellers were tourists, with the remainder primarily travelling on business or visiting friends or family. All were adults and almost all reported experiencing their first bout of dengue. They reported having a fever, fatigue, pain and a headache, with the fever lasting nearly a week on average.

Burden of dengue on travellers

Only 20 of the travellers stayed in hospital while they were abroad; they stayed for an average of 3.7 days. Of the remainder, 29 visited a pharmacy or doctor’s office. The majority – 64 in total – visited an outpatients department, doctor or healthcare clinic on their return home, and 35 spent an average of 3.1 days in hospital in their home country. One returning traveller spent seven nights in intensive care.

The researchers estimated that each traveller incurred out-of-pocket costs averaging $993. “We looked at it from the patient’s perspective, what they paid,” says Professor Tozan. “They told us about both direct and indirect costs at home and abroad, including drug, hospital and other medical costs, along with the cost of cutting travel or staying for extra days. Some paid for family to come and spend time with them – or even to evacuate them.”

The study opened the door to a larger piece of research looking into the burden of dengue, chikungunya and malaria across more countries for a longer period. Entitled ‘Monitoring long-term consequences of chikungunya, dengue, Zika and falciparum malaria in travellers’ and with the identity ‘CHIDEZIMA’, the study – which is currently recruiting participants – aims to “describe and compare the symptoms, functional activities, healthcare consumption and quality of life” of travellers who are “at the acute state of infection”. A sub-study will look at “the economic burden of illness due to these travel-associated, tropical febrile infections by international travellers”.

Burden of dengue on society

Besides this more extensive study, there is still more to explore. After all, the out-of-pocket costs incurred by travellers are just one piece of the puzzle. “We’re missing the healthcare component,” says Professor Tozan. “We need to drill into one country and match the patients’ out-of-pocket costs with the treatment they received in their home country to get a more comprehensive picture of what one traveller’s dengue illness episode could cost society.”

While the costs are likely to be different in each country, the researchers estimated they could amount to more than US$7k, US$8k and just short of US$3.5k per patient for the US, Australian and Italian healthcare systems, respectively. They derived these ballpark estimates from average national costs for healthcare.

If we add together the almost US$1k cost to the patient and the US$7k cost to the US healthcare system, that’s a potential cost of US$8k for each episode of uncomplicated dengue – which is significant. Costs for an episode of severe dengue would be far, far higher. And if enough of those travellers were to bring dengue back to a region with a population of Aedes mosquitoes capable of transmitting the disease, it could lead to an outbreak.

Europe now has mosquito populations capable of transmitting the disease. Just imagine the financial burden of a dengue outbreak!

Dengue prevention essential

“We now have the financial argument that shows why preventative measures are so important for travellers. We need to tell people what they need to do when they are travelling to dengue-endemic regions, let them know that the burden of dengue is high. Once a vaccine is available for travellers, getting a shot before you travel will be a no-brainer,” concludes Professor Tozan.

Have you experienced an episode of dengue while travelling abroad? Please tell us your story. How were you diagnosed? What treatment did you receive? How are you now?