- by Alison Booth

Dengue epidemic in the Philippines: Is the worst still to come?

The Philippines Department of Health (DOH) declared a National Dengue Epidemic on 6th August 2019. Dengue cases in the country had almost doubling compared with the first seven months of 2018 – a year that was itself considered an extreme year for dengue. With the only licensed dengue vaccine banned, what’s behind this year’s worrying dengue epidemic?

By 27th July, the number of dengue cases recorded in the Philippines in 2019 had reached

167,607, with 720 fatalities, according to a World Health Organization (WHO) situation report. While all four serotypes are circulating, laboratory tests have confirmed that DENV 3 is the biggest culprit, responsible for 72% of cases. The average age of people infected is 12 years old with just under a quarter (23%) of cases and more than half (52%) of fatalities in children between the ages of five and nine.

 

Dengue case numbers expected to rise

Dengue is endemic in the Philippines, occurring throughout the year. Transmission is generally highest between June and October, peaking in August, which tends to be the rainiest month of the year. But a weak El Niño has delayed the rains this year, pushing back the peak of the dengue season.

We spoke with Lulu Bravo, Professor of Pediatric Infectious and Tropical Diseases at the University of the Philippines in Manila, to understand what’s behind the current dengue epidemic in the Philippines.

“In the Philippines, we expect to see increased incidence of dengue every two to three years,” said Professor Bravo. “This has been happening for the past 50 years. But this year we have already seen nearly 200,000 cases when we are only eight months into the year; so we can expect something nearer 250,000 cases in 2019. It will be a record high.”

Indeed, data from the nation’s DOH shows how peaks in dengue case numbers have been rising, and that 2018 has been the worse year this decade with just over 216,000 dengue cases reported throughout the year.

 

How is the country reacting?

The DOH declared a National Dengue Epidemic on 6th August. It has urged all regional DOH offices to increase dengue surveillance, case management and outbreak response. It is also encouraging clean-up drives along with vector control in health facilities and communities. “There are lots of radio and TV announcements and interviews by the health officials to raise awareness on dengue prevention and better control,” she says. “The Aedes mosquito breeds in moderately clean water, not the dark or stream water; it’s mostly stagnant rainwater, clean water on the roof.”

People are acting on the advice given, removing mosquito breeding sites by taking away water containers that are not covered, changing the water in flower vases, and generally keeping the environment clean.

Professor Bravo emphasises the importance of knowing the warning signs and getting medical attention quickly: “We need to be conscious of the warning signs that dengue could present. If you see any of these signs, seek consultation early because that’s the only way to prevent severe dengue and progress to a shock syndrome.”

 

Is the Dengvaxia ban to blame?

Media reports are blaming the government for banning the sale and distribution of Dengvaxia, a dengue vaccine made by Sanofi Pasteur, in February. The Guardian claims: “[Dengue] cases have gone up 98% after the government banned a vaccine widely blamed for causing the deaths of children.”

The Professor has a very different perspective. She explains: “The epidemic is not due to the banning of the vaccine. Dengvaxia has been stopped from being used in the Philippines since December 2017, that’s more than a year and a half ago. It had been administered to almost 800 children and adults.”

Scientists, Professor Bravo tells us, believe urbanisation has brought about the increasing incidence of dengue. She explains: “People are clustering in urban areas. Transmission is going to be high in places where there are lots of people.”

She also reveals how and why climate change has been blamed. “Mosquitoes want to breed where there are wet and humid places. The Aedes aegypti mosquito that is responsible for the dengue virus transmission can now survive in places that may not have been affected by dengue before – even in temperate countries.”

Read: Double dengue: Why a second dengue infection is worst than the first – and what it means for vaccination

 

Will the dengue ban be lifted?

Dengvaxia, she notes, is licensed in at least 21 countries, including the United States and the European Union. “The vaccine has been withdrawn in the Philippines for an administrative, not a safety, reason,” says Professor Bravo.

A recent DOH press release announcing the outcome of Sanofi Pasteur’s appeal against the Dengvaxia ban states that the DOH “has upheld the Food and Drug Administration’s (FDA) permanent revocation” because of “the continued failure of manufacturer Sanofi Pasteur to submit post-approval requirements.” Interestingly, it also notes that “the efficacy of the Dengvaxia itself is not an issue in this case.”

There is still hope in the Philippines that the Dengvaxia ban may one day be lifted. “People here are still trying to figure out how to make this vaccine available again so that it can be made useful for those who have had the dengue before,” says Professor Bravo. “The WHO has recommended that if you are already positive for dengue, then the vaccine is for you.”

Read: Wanted – a simple test for dengue fever 

People travelling to dengue-endemic areas are also showing interest in the vaccine. Professor Bravo has advice for travellers looking for a dengue vaccine: “This first generation dengue vaccine is not for travellers or a rapid response to an outbreak. It has a maximised duration for effectivity of about one year, and it requires three doses over six months. Scientists are working on developing something better.”

Dengue is a complicated disease. For every person with symptomatic or severe dengue, there will be four who have mild or no symptoms at all. With dengue not only on the rise in the Philippines but also spreading across the globe, more needs to be done to protect people from dengue.

If you’re currently in the Philippines, share your experience of the current dengue epidemic.