CLIMATE CHANGE MAY BE CAUSE OF SURGE IN DENGUE FEVER CASES AROUND WORLD
▶ Doctors in the UAE warn of patients testing positive for disease despite no history of travel, writes Nick Webster
Global cases of the debilitating tropical disease dengue fever are increasing sharply – including rises in some Arab nations, experts said. Dengue fever is a waterborne disease spread by mosquitoes and is rarely reported in the Emirates. More than 4.2 million cases were recorded worldwide last year, compared with 500,000 at the turn of the century, said the University of Washington’s Institute of Health Metrics and Evaluation.
The European Centre for Disease Prevention and Control (ECDC) said last year that 6,000 dengue-related deaths were reported in 92 countries and territories worldwide.
The Mena region registered an 88 per cent increase in cases between 1990 and 2019, the institute said.
It found 1.2 million more incidences of the virus were reported in the World Health Organisation’s Eastern Mediterranean region in that time.
This region comprises 21 member states – including the UAE – plus occupied Palestine. The region stretches from Morocco to Pakistan.
Medics in Dubai said that although cases of dengue fever patients requiring care were low, some had been reported recently – including patients who appeared to have contracted the disease locally.
“In 2023, we saw an increased surge in vector-borne disease,” said Dr Nandkishore Mariswamy, an internal medicine specialist at NMC Specialty Hospital in Dubai Investments Park.
“At the end of the summer, we saw multiple cases of local spread of dengue in Dubai, which was very surprising.”
Dengue fever is usually spread by the Aedes aegypti mosquito – often referred to as the yellow fever mosquito.
In the past, it was unheard of in Dubai, said Dr Mariswamy.
He suspects that climate change is allowing the carrier species to establish itself in more places.
“Usually, whenever there is a weather change or climate change, we find that warmer climates favour these vector-borne mosquitoes to thrive,” said Dr Mariswamy.
Highest number
The WHO says dengue fever was first reported in the Eastern Mediterranean region in 1998. Nine countries – Egypt, Oman, Saudi Arabia, Somalia, Sudan, Yemen, Pakistan, Afghanistan and Djibouti – have had outbreaks.
Pakistan, Saudi Arabia and Oman reported the highest number of cases last year.
While the Emirates Health Services website has not published any recent dengue data, the site has a page providing information, including preventive measures.
Elsewhere in the region, an outbreak was reported last summer in Egypt, particularly in the south-eastern Red Sea governorate.
Meanwhile, research by the department of biology sciences at the King Abdulaziz University in Jeddah found that the number of dengue cases soared in Saudi Arabia lsat year.
Data showed infections reached 4,099 in the first half of the year – a significant increase on previous years in the kingdom, said researchers.
Only 300 cases were reported in Jeddah in 1994, when surveillance was established.
Fever reaching 40°C
Infection in humans is caused by any one of four closely related dengue viruses that lead to a variety of symptoms. While vaccine research is continuing, the four subtypes of the virus make it a challenge to develop effective protection.
The most common signs are a fever of 40°C, headaches, joint and muscle pain, nausea, vomiting, mild nosebleeds and a skin rash.
Severe cases in vulnerable groups – such as pregnant women, the young, the elderly and people with existing health problems – can be deadly if untreated.
In 2019, the WHO warned that an increase in global outbreaks was probable, particularly during seasonal changes and periods of heavy rainfall.
“With waterborne diseases, most of the time it causes abdominal symptoms like diarrhoea, vomiting and severe dehydration,” said Dr Ali Ahmed, from the Canadian Specialist Hospital in Dubai.
“If someone is affected by the disease or their immune system gets activated, they are in a compromised situation.
“When a patient comes with symptoms like high fever, we check for dengue, as it usually presents with a very high temperature of 39°C or 40°C.”
Doctors check a patient’s platelets – cell fragments in the blood that prevent heavy bleeding. A low count could signal internal bleeding, another symptom.
An antigen blood test would follow to confirm the presence of the pathogen, before the case is reported to the health authorities.
Dr Ahmed said he recorded about 25 cases of dengue fever in his hospital last year, having typically reported about five cases a year previously.
Patients testing positive for the virus had no history of travel, indicating dengue fever was contracted in the UAE. “There have been more cases here than in previous years, and I’ve had that confirmed in discussion with other doctors,” said Dr Ahmed. “We’re seeing dengue cases every year, whereas before we didn’t see any.”
Many recently reported cases appear to be in Dubai, where people who have contracted dengue have taken to social media to warn others to be on guard for mosquitoes.
In October, Al Zahra Hospital in Dubai published details of a 58-year-old woman with the disease who had no history of travel outside the UAE.
“We have been seeing dengue fever every now and then, with most cases coming from endemic countries,” said Dr Dima Ibrahim, an infectious disease specialist at Burjeel Medical City in Abu Dhabi.
But she said fellow doctors now reported cases in patients who had not travelled.
“It was almost unheard of to have this disease in the Middle East and North Africa because of the dry air,” Dr Ibrahim said. “Some colleagues have described cases to have occurred without any history of travel, like in Dubai.”
Once doctors at BMC suspect dengue fever based on symptoms and tests, cases are reported to the Department of Health. Hospitals offer supportive treatment, such as medication for headaches.
“There is no specific treatment that we give for dengue,” said Dr Ibrahim.
“The weather change has made the presence of mosquitoes more prevalent, so we must try to prevent transmission of the disease. If there is an area with mosquitoes, apply insect repellent to the skin and, sometimes, bedding. If you have activity outdoors, wear long sleeves.”
Warming planet
As the planet warms, infectious diseases could undergo a major shift, experts say.
More frequent drought and floods expose populations to more waterborne microbes, while migrating animals interact with species they had not encountered before.
Longer summers and shorter, warmer winters with more standing water, in which mosquitoes breed, are increasing cases of vector-borne diseases.
“Clinicians need to be ready to deal with the changes in the infectious disease landscape,” said Prof George Thompson, from the department of medical microbiology and immunology at the University of California’s Davis School of Medicine.
“Learning about the connection between climate change and disease behaviour can help guide diagnoses, treatment and prevention of infectious diseases.”
At the end of the summer, we saw multiple cases of local spread of dengue in Dubai, which was very surprising
DR NANDKISHORE MARISWAMY NMC Specialty Hospital in Dubai