Dengue outbreak raises concerns in Saudi Arabia as mosquito numbers surge

Saudi Arabia is grappling with a surge in dengue fever cases, leading to growing concerns among health authorities who say intensified efforts are needed to control outbreaks and raise awareness on preventative measures.

The virus is spread from the bite of an infected Aedes mosquito, primarily the Aedes aegypti species, which thrives in tropical and subtropical climates. It spreads dengue and other viruses, including Zika, making it one of the top three mosquitoes in the world in terms of the number of diseases it can spread.

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Experts say Saudi Arabia is annually reporting thousands of cases of dengue fever, common symptoms of which include fever, rash, nausea, and aches and pains that can last up to a week. Some people with dengue develop complications that can result in internal bleeding, shock, and even death. Severe dengue requires careful monitoring in the hospital.

Saudi-born dengue fever expert, Assistant Professor of Environmental and Occupational Health at the Kingdom’s King Saud University and the head of the Public Health and Preventive Medicine Unit, Dr Kholood Altassan, told Al Arabiya English that she has been studying dengue fever across the country since 2016.

She explained that increase in cases is driven more by urbanization and mosquito resilience than climate change, though rising temperatures enable the spread to new areas.

“The mosquito habitat has been expanding over the last 20 years. Even its presence in Saudi Arabia is somewhat non-novel and anomalous, and it’s surprising to many people within the field in Saudi Arabia. Historically, we’ve seen these types of mosquito-borne diseases in the malaria belt or in tropical climates, so it’s odd to see it in a dry, arid environment like that of Saudi Arabia.”

Urbanization drives mosquito migration inland

Altassan said she had approached the Saudi Health Ministry years ago to ask what climate-related diseases are most concerning to them. Their answer: Dengue fever.

She said the disease first arrived in Saudi Arabia in late 1993 or early 1994. At the time, the arid climate was deemed inhospitable for the Aedes mosquito vector. Yet, it managed to gain a foothold and become endemic in the Western Region.

“When that happened, they were surprised it had managed to take hold because the climate wasn’t suitable. We’re now understand more and more is that even if the climate is not necessarily ideal, this particular mosquito – the Aedes aegypti – is very resilient and very much able to withstand dry conditions for longer periods, and it’s able to find environmental microclimates in an urban environment where it can thrive and flourish,” Altassan explained.

Dengue fever – while prevalent in Saudi Arabia for 20 years – is now moving further inland to capital cities.

“When I did my research, there were no Aedes aegypti in Riyadh and no Aedes aegypti outside the Western Region. In 2021, Saudi Arabia published a paper stating that for the first time, there were Aedes aegypti in Riyadh.”

This year, Saudi Arabia has seen cases without travel history to endemic areas, indicating local transmission and “that is new,” Altassan said.

Hot and humid weather provides an ideal breeding ground for disease-carrying mosquitoes like Aedes aegypti. Warmer temperatures have expanded their habitat, enabling them to spread to previously unaffected areas.

Rainfall creates breeding grounds

Increased extreme weather events, such as floods, also create stagnant water pools where mosquitoes breed. Saudi Arabia has seen unusually heavy rainfall in recent years, fueling mosquito breeding.

According to the 2023 study ‘Knowledge, attitude, and practices toward dengue fever among the public: A cross-sectional study in the Western region of Saudi Arabia,’ published in the Frontiers journal, author Munerah Hamed noted that the Western region of Saudi Arabia experienced a series of substantial rainfall events between 2017 and 2023, resulting in a rapidly advancing dengue epidemic in the area.

“Winter rainfall creates conducive breeding environments for dengue mosquito vectors, increasing transmission rates. On the other hand, summer heat accelerates the mosquito life cycle and enhances viral replication, heightening the risk of dengue transmission,” Hamed observed.

The World Health Organization has noted in its latest infectious disease advisory that dengue cases are rising.

“After a slight decline of cases between 2020-2022 due to the COVID-19 pandemic and lower reporting rate, in 2023, an upsurge in dengue cases has been observed globally, characterized by a significant increase in the number, scale, and simultaneous occurrence of multiple outbreaks, spreading into regions previously unaffected by dengue. Outbreaks are also reported in middle and high-income countries such as Egypt and Saudi Arabia due to climate change leading to unusual rainfalls.”

Studies suggest more than eight billion people could be at risk of dengue and malaria by 2080 as warming temperatures enable spread. The WHO notes that dengue is one of the top ten global health threats, calling it the most rapidly spreading mosquito-borne virus, with cases increasing 30-fold over the past 50 years.

Surge in cases

Saudi Arabia, in particular, has witnessed a significant increase in dengue fever cases in recent years. According to the Saudi Ministry of Health and the WHO, reported cases have surged recently, underscoring the urgent need for effective measures to combat the disease.

Saudi Arabia’s Ministry of Health Statistical Yearbook 2002 – the latest year on record – recorded 3,647 cases across the Kingdom. In 2023, the WHO noted that Saudi Arabia was one of the top three countries for reported dengue fever cases in the Eastern Mediterranean Region.

In a 2023 study, ‘Prevalence of dengue fever in Saudi Arabia: Jeddah as a case study,’ Hanan Alyahya, author of the report published in the Entomological Research journals, noted that 2023 saw a surge in cases of dengue fever: “The first recorded case in Saudi Arabia was in October 1993. However, daily data indicates that 2023 was a major epidemic year. The number of infections reached 4,099 during the first half of the year, indicating a significant increase compared to previous years.”

Stacey Rizza, an infectious diseases specialist and professor of medicine at Mayo Clinic, told Al Arabiya English that Saudi Arabia has gone from “what was probably only a few hundred cases annually 20 years ago, to thousands a year now. “

“They’ve had a 10 times, if not more, increase in dengue cases because of the differences in water transmission and rainfall.”

She said that dengue fever predominantly causes problems in central parts of the world around the equator that are moist and have a lot of mosquitoes.

“Because of climate change and the way environments have changed in the last 25 years, the number of cases has dramatically increased, and that’s why it is getting more and more attention,” she said.

“Cases have been increasing because the world is getting warmer and more moist. The disease had been common around India, Southeast Asia, the Americas and the Caribbean but has now started to move to new parts of the world, particularly the Eastern Mediterranean and parts of the Gulf States.”

The region had very few cases 20 to 25 years ago, said Rizza.

“But the areas around the Red Sea have started getting heavier rains, and sometimes there’s flash flooding or implications that can allow stagnant water, mosquitoes and then transmission of dengue.”

This will also see dengue appear in neighboring Gulf countries, she said.

“The UAE is still a little drier and doesn’t get those heavy rains like those around Jeddah and the Red Sea. But the UAE is a multi-dimensional country with people from all over the world. They’re likely to notice a small increase in the near future.”

Altassan said despite the rise in cases, dengue fever is “not the next pandemic” given that, unlike other diseases, such as COVID-19, it can only be spread via the vector – the mosquito – rather than human-to-human transmission.

“Diseases that have the potential to become a pandemic are those that can spread from person to person. With dengue, you still need the vector. So, as long as there is some sort of a middleman, it is unlikely to spread exponentially out of control.”

However, massive outbreaks could still overwhelm health systems.

Virus resilience despite control efforts

Eliminating mosquito breeding grounds is crucial, but the resilience of Aedes aegypti makes this problematic.

Altassan pointed out that once a vector exists, “it is tough to eradicate.” She said: “There are a lot of challenges when it comes to vector control, both globally and locally.”

She pointed to four types of vector control, starting with either mosquito nets or mosquito ‘zappers’ for home.

“The problem with mosquito nets is that you use them while you are sleeping – and with the Aedes aegypti species, that’s not helpful. They are usually day-biters. They usually bite early in the morning and right before the sun sets in the afternoon. That is the peak biting time,” she further explained.

Other means of outbreak control are mostly limited to chemical broad-spectrum insecticide sprays, which come “with its own set of challenges” as they can harm both humans and non-target animals and insects.

“Plus, there is the fact of resistance. Every year, you have to test the mosquitos to see if they are going to be sensitive to this pesticide. Do we need to change it or not?”

According to Altassan: “You have to do targeted spraying because the mosquito is present in small waterbodies. People generally store water in small containers around their houses. So, for example, in air conditioning units where water collects, these mosquitos will lay their eggs in these areas. So, when you spray, you have to target these specific areas.”

Saudi Arabia’s vast population and geographic size also present a challenge.

“What they used to do in Jeddah was if you got a case of dengue fever, they would send a team to your home, investigate, and see where there might be breeding points. But, from a human resources point of view, it is not very sustainable. Moreover, it is very difficult to carry out such a search for every single case,” Altassan further said.

Genetically modified mosquitos may help

But, she said, new, more novel ways “seem promising” – including the release of genetically modified mosquitos.

This is where scientists produce large quantities of male Aedes aegypti eggs within a laboratory setting. These males are engineered to harbor a specific gene, which they transmit to their progeny during mating in their natural habitat. The gene is engineered to eliminate female offspring, primarily females that bite and transmit diseases. Male offsprings continue to propagate the gene through subsequent mating cycles.

This initiative aims to reduce the transmission of mosquito-borne illnesses to humans gradually. Its purpose is not to halt an outbreak, but to avert one.

“However, because it’s still so novel, the long-term impacts are not clear yet, and they haven’t been applied in a sustainable and consistent way,” she noted.

Altassan also said that surveillance of dengue fever is “extremely challenging.”

“It is one of the most grossly underreported infectious diseases. Because roughly 80 percent of cases are asymptomatic, you will contact it, and you won’t know. Then, if you are asymptomatic, you can transmit it to other mosquitos, so the spread can still occur,” she said.

“In other cases, it will be a mild flu-like virus, which people will treat themselves symptomatically with over-the-counter medication and won’t even seek medical attention. That means, you are often not going to detect these cases. If we say 95 percent of cases are like that, are we only detecting five percent?”

“So, Riyadh may have had dengue years ago, but we didn’t realize it because it wasn’t a big enough outbreak. In other cases, we might detect an outbreak, but won’t realize its magnitude.”

This will also see dengue appear in neighboring Gulf countries, she said.
“The UAE is still a little drier and doesn’t get those heavy rains like those around Jeddah and the Red Sea. But the UAE is a multi-dimensional country with people from all over the world. They’re likely to notice a small increase in the near future.”

Rizza told Al Arabiya English that the only way to prevent dengue fever is to be methodical about preventing mosquito infections.

“Health officials have significant initiatives to eradicate stagnant water, chemical treatments and areas that carry a lot of mosquitoes. An example is requiring people not to keep big open water areas because this will decrease the amount of mosquitoes that can live and therefore cause transmissions.”

“In more crowded urban areas, when multiple people live in the same household, the risk of dengue could increase.

The virus will be transmitted faster in areas that don’t have good water flow or good drainage systems or have more stagnant water and mosquitoes. And then, of course, there is the issue of access to healthcare to get diagnosed and receive supportive care if needed.”

Describing the symptoms of dengue fever Rizza added: “It makes people/patients have high fevers. It can cause body aches, particularly in the muscles and joints, and can feel like pain to the bones, which is why its nickname is “bone-ache fever.”

Some people say it makes their eyes hurt -- that they feel pain behind their eyes. It can also cause some nausea and vomiting and can last up to one to two weeks, although the worst of it is usually in the first few days or the first week. It can cause additional symptoms, such as liver dysfunction, which may cause the whites of a person’s eyes to turn yellow. It can also cause a rash and swollen lymph nodes.”

If infected, the Saudi Ministry of Health advises Saudi citizens to “get enough rest, take enough fluids, avoid blood-thinning medication such as aspirin and avoid exposure to mosquito bites to avoid spread of the disease.”

Prevention hinges on public awareness

Public awareness campaigns play a crucial role in combating dengue fever, with the Saudi Ministry of Health saying: “The best way of prevention is to avoid mosquito bites by eliminating mosquito breeding sites, such as indoor and outdoor water basins; covering, replacing and cleaning all water tanks and deposits every week, including household vase water; using insect repellent skin creams indoor and outdoor; covering the body with long-sleeved clothing; and making sure window screens are intact and free of holes that can allow insects in.”

The Saudi government has launched extensive awareness programs to educate the public about the disease, its symptoms, and preventive measures. These campaigns emphasize the importance of personal protection, such as wearing long-sleeved clothing, using mosquito repellents, and eliminating stagnant water sources.

Yet, according to Altassan, public knowledge about the disease still needs to improve in many parts of Saudi Arabia.

She said that while public health centers and clinics in the Western Region and Jeddah have done “an amazing job – there are education materials in hospitals, in schools, everywhere” in educating the public. This now needs to be widened across the Kingdom as the disease begins to crop up in other, previously unreported parts of the country.

“In Riyadh, no one has heard about dengue. They don’t know what the disease is or how it is contracted. There is more we need to start doing [in terms of awareness drives] outside the Western Region,” she added.

Treating dengue fever

There is no treatment for dengue itself, only supportive care for the symptoms.

“In one percent of cases, it can be quite severe,” says Altassan. You can get a severe hemorrhagic fever. All we can do at the hospital is treat the symptoms. If someone goes into hemorrhagic shock, you are going to treat the hemorrhagic shock.”

She further said: “If that was one percent out of 100 people, it doesn’t seem that concerning, but one percent out of hundreds of thousands of people is. It depends on the magnitude of the outbreak. And the problem is, once it takes hold in an area, you will likely struggle to bring those numbers down again for years.”

Rizza said “the main thing to do” is for those infected to drink lots of fluids to stay well-hydrated.

“Take acetaminophen to help with bone pain or muscle pain. Occasionally, it can progress to severe disease requiring people to go to the hospital to receive IV fluids, go on ventilators or receive other supportive care because they’re critically ill.”

She added: Getting infected does not mean a person is immune from getting infected again. It tends to be worse if a person gets infected a second time. Dengue can cause death in very severe cases.”

There is a vaccine available globally, but it is not used in Saudi Arabia, says Altassan. It is only recommended in areas of very high incidence of dengue fever and can have adverse health effects.

“They applied one vaccine, but then they realized that it actually makes dengue fever worse the first time you contract it. So, it doesn't work.”

Alex Jackson, the global editorial editor for the World Mosquito Program, told Al Arabiya English that extreme climate and weather patterns such as droughts, heatwaves, floods, and rainfall are increasing in severity and regularity, providing favorable conditions for mosquitoes to breed.

“This could help spread their viruses to higher latitudes and altitudes across the globe, reaching new regions and re-emerging in areas where mosquito numbers had subsided for decades,” he said. “Although there are more than 3,000 mosquito species in the world, most serious diseases such as dengue, chikungunya, Zika, and yellow fever are transmitted by just two – Aedes aegypti and Aedes albopictus.”

Jackson added: “Dengue, the fastest-spreading mosquito-borne virus in the world, is estimated to infect up to 400 million people every year, with more than half of the world’s population now at risk. Recent studies have predicted that more than eight billion people could be at risk of malaria and dengue by 2080.”

Earlier this month, Al Arabiya English reported that a new study shows that climate change is accelerating the spread of deadly infectious diseases such as malaria and dengue fever beyond their traditional geographical boundaries.

The research from the University of California-Davis School of Medicine, published on Monday in the journal JAMA, rings alarm bells about the complex interplay between rising global temperatures and the changing epidemiology of viruses, bacteria, fungi, and parasites.

Calls for greater preparedness

It calls for greater preparedness by the medical community to deal with emerging health threats caused by climate change.

“Clinicians need to be ready to deal with the changes in the infectious disease landscape,” said study lead author George Thompson, a professor at the UC Davis School of Medicine.

“Learning about the connection between climate change and disease behavior can help guide the diagnosis, treatment, and prevention of infectious diseases,” Thompson noted.

Director of Scientific Affairs at the World Mosquito Program Dr Katie Anders told Al Arabiya English: “We need to use all the tools in the box to combat the growing threat from mosquito-borne diseases.”

“This means governments and communities must control mosquito populations, strengthen disease surveillance and outbreak response, ensure good clinical management, and rapidly scale up the delivery of effective interventions such as Wolbachia and new dengue vaccines once those are available.”

Read more:

‘Worst dengue season’: UN tells Latin America, Caribbean to prepare for epidemic

Climate change fuels spread of deadly diseases, scientists warn

Dengue can be major threat in US, Europe and Africa as temperatures climb: Scientist