How Humans Are Laying Out The Welcome Mat For Mosquitoes And The Diseases They Carry

Climate change is partly to blame, but it’s not the whole story.
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PENANG, Malaysia – The buzz of a single mosquito flying around Oo Boon Siew’s living room is enough to make his family jump in terror. It wasn’t so long ago that these tiny insects disrupted their tranquil life and nearly killed Oo.  

Once a well-travelled education consultant, Oo now lives on the Malaysian island of Penang with his wife and son. His joints frequently swell and ache, a physical reminder of the events that brought him to the edge of death.

Over the course of just a few weeks in 2009, Oo fell victim to a staggering sequence of viruses. First, he was infected with the flu-like dengue fever, fairly common in this part of the world. Then he caught the less common chikungunya, which is similar to and often confused with dengue but can cause disfigurement and disabling joint pain that persists for years. Finally, he caught a more severe strain of dengue and nearly died.

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Oo Boon Siew, 58, at his home in Penang, Malaysia.
Joshua Paul for Huffington Post

There is no cure for dengue or chikungunya, and both spread via the same two species of mosquito that carry the Zika virus.

Though Oo’s experience was unusual, it illustrates how these mosquito-borne diseases spread on the backs of urbanization, globalization and climate change. Such illnesses, which have expanded across the world increasingly in the past decade, are making inroads into Europe and the Americas, raising fears among experts that outbreaks could become more severe.

The legacy of Oo’s illnesses are still evident in his family’s home. The family always keeps two large cans of insecticide at hand. Oo’s son, Adrian, even decided to research chikungunya for his doctorate.

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Mosquito repellants on the staircase of Oo's house.
Joshua Paul for Huffington Post

And then there are the memories.

When Oo first fell ill with dengue, his temperature was so high that he stayed in the hospital for a week. After a couple more weeks, he was sick again ― they thought it was related to the dengue, but his joints were swollen and his eyes hurt. When his temperature spiked, he went back to the hospital and tested positive for chikungunya, which was then sweeping through his neighborhood.

“My hands hurt so much that I couldn’t hold a spoon,” Oo said of his chikungunya. “I couldn’t hold a cup.”

He recovered quickly after the first week of chikungunya, but only weeks later a third mosquito bite delivered a dangerous form of dengue. Oo had never felt so sick. Doctors told him he’d need blood transfusions to keep him strong while the virus raged inside him.

That last fight was the toughest. But at least he recovered. Others have not been so lucky.

As extreme weather events like massive floods and storms become more common, conditions grow more favorable for mosquitoes to breed, and more mosquitoes mean more of the diseases they carry. But some scientists warn it would be simplistic to blame climate change alone for the expansion of mosquito-borne diseases. Instead, they point to a variety of interconnected factors that allow mosquitoes to thrive, including the effects that human activities can have on ecosystems, such as rapid urban construction, deforestation, mass migration and political and economic instability. 

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High-density condominiums and houses built on a newly cut hill in Penang.
Joshua Paul for Huffington Post

Scientists are also concerned that cases of chikungunya, dengue and Zika are being under-reported. Some infected people may have mild symptoms or no symptoms at all. Nevertheless, these diseases are suddenly more visible than they’ve been in the past.

Dengue is one the fastest-growing infectious diseases in the world, and the World Health Organization says there may be as many as 390 million new cases each year.

The human Zika virus infection, initially endemic in equatorial Africa and Asia, has also expanded its geographical range. In 2007 it emerged in the Pacific region and the Americas as a more serious infection than previously reported.

Also in 2007, chikungunya transmission was reported for the first time in Europe: 197 cases in the Emilia Romagna region of northern Italy. The disease had mostly occurred in Africa, the Americas, the Indian subcontinent and wide areas of AsiaLast year, the WHO reported outbreaks in Italy and France.

In 2013 the disease re-appeared in the Caribbean after 200 years. Since then, local transmission has been identified in 45 countries or territories throughout the Americas, with more than 1.7 million suspected cases reported to the Pan American Health Organization. 

Chikungunya went undetected for seven years in Malaysia between 1999 and 2006, which led to speculation it had been eliminated. But it then re-emerged in a reported outbreak in the country’s north, reaching 13,759 reported cases by 2009. The disease now returns in regular outbreaks. Last year, a team of researchers from the University of Malaya (which included Adrian Oo) reported 269 cases, mostly in the north.

Oo Boon Siew is a living testament to the resurgence of chikungunya in his homeland: He holds out his hands, the knuckles swollen even after eight years. He feels pain in his joints about once a month. It’s sometimes worse during the rainy season.

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Oo Boon Siew's hands, which he says still experience joint pains due to chikungunya.
Joshua Paul for Huffington Post

“My son, Adrian, forbids me to complain now that he studies it,” Oo said of the disease. “He explained that for some people it is much worse.”

Adrian, now 25, was taking his high school exams when his father became sick. Those months left such an impression that he decided to study medicine and specifically to research chikungunya.  

Chikungunya is more often found in rural areas of Malaysia, but the area where the Oo family lives could hardly be called rural. The picturesque island of Penang has experienced an explosion of new construction in recent years. Building sites now scar a landscape previously thick with forests. This growth benefits businesses and tourists, but also disease-carrying mosquitoes, which thrive in urban environments with numerous construction sites.

Floods are also more common now in Penang, helping to fuel the insect problem.  

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A lake in Penang muddied from flooding.
Joshua Paul for Huffington Post

Oo says he’s never been sick like he was in 2009. “That’s when they started building all around the area where I live, and stagnant water from building sites was a breeding camp for mosquitoes,” he said.

Adrian now forbids his parents from going on runs in the park during the rainy season.

“My wife and I used to go very often. But now there’s no discussion, Adrian feels it’s too dangerous,” said Oo.

Around the world, disease-carrying mosquitoes are developing resistances to the most common insecticides, including those used to fumigate buildings when an outbreak occurs, according to Dr. Low Van Lun, a senior lecturer on tropical diseases at the University of Malaya in Kuala Lumpur.

Recent studies have looked at genetically modifying mosquitoes and releasing sterilized males. “But some are afraid it will affect the ecosystem, killing frogs for example, while the long-term consequences are unpredictable and we could be left with only very strong mosquitoes and the consequences of the bite are unknown,” Dr Low said.

For now, Oo is the only one in his family who can laugh at the sight of a mosquito. People who have already had chikungunya or strains of dengue are likely to develop immunities, so he probably won’t get those diseases again. His wife and son are still vulnerable, however.

“They are terrified, but I had everything already, so I’m the only one who’s not afraid,” he said.

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Oo outside his house in Penang.
Joshua Paul for Huffington Post

This article is part of HuffPost’s Project Zero campaign, a yearlong series on neglected tropical diseases and efforts to fight them. The series is supported, in part, by funding from the Bill & Melinda Gates Foundation. All content is editorially independent, with no influence or input from the foundation.

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Before You Go

Neglected Tropical Diseases
Lymphatic Filariasis(01 of18)
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Lymphatic filariasis, more commonly known as elephantiasis, is a leading cause of disability worldwide, according to the U.S. Centers for Disease Control and Prevention. It affects over 120 million people globally and can cause severe swelling of body parts, including the legs and scrotum. While people are usually infected in childhood, the painful, disfiguring symptoms of the disease only show up later in life. (credit:Drugs for Neglected Diseases initiative)
Onchocerciasis(02 of18)
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Onchocerciasis, commonly known as river blindness, is an eye and skin disease that can cause severe itching and visual impairment ― including blindness. Around 18 million people are infected. Of those, over 6.5 million suffer from severe itching, and 270,000 are blind. The disease is caused by a parasitic worm, transmitted through bites from infected blackflies. The worm can live for up to 14 years in the human body, and each adult female worm can be more than 1.5 feet long. (credit:ISSOUF SANOGO/AFP/Getty Images)
Chagas(03 of18)
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Chagas disease is a potentially life-threatening illness. In the first months after infection, symptoms are mild, including skin lesions and fever. But in its second, chronic phase, up to 1 in 3 patients develop cardiac disorders, which can lead to heart failure and sudden death. The disease is transmitted to humans by “kissing bugs,” which live in the walls or roof cracks of poorly constructed homes in rural areas, according to the World Health Organization. Of the estimated 6 million to 7 million people affected worldwide, most live in Latin America, but the disease has also spread to the United States. Around 300,000 people in the U.S. have Chagas disease, according to the Dallas Morning News. (credit:Nature Picture Library/Getty Images)
Dengue(04 of18)
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Dengue is a flu-like illness that can sometimes be lethal. In 2015, more than 2 million cases of dengue were reported in the Americas. In some Asian and Latin American countries, “severe” dengue is a leading cause of serious illness and death among children. Dengue is spread by the Aedes aegypti mosquitoes, the same type of insect that transmits Zika. To reduce the risk of bites, WHO recommends covering water containers, using insecticide, having window screens and wearing long sleeves. (credit:Fachrul Reza/NurPhoto/Getty Images)
Human African Trypanosomiasis(05 of18)
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Human African trypanosomiasis, commonly known as sleeping sickness, is a chronic infection that affects the central nervous system. People can be infected for years without signs, but in the second stage, patients can suffer behavior changes, hallucinations and even slip into a coma and die. Many people affected live in remote, rural areas that don’t have easy access to quality health services. This makes diagnosis and treatment more difficult. WHO has identified sleeping sickness as a disease that could be eliminated worldwide by 2020 if the right resources are dedicated to it. (credit:MARIZILDA CRUPPE / DNDi)
Leishmaniasis(06 of18)
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There are several forms of leishmaniasis, including visceral, which can be fatal, with symptoms including fever and weight loss; and cutaneous, the most common form, which causes skin lesions, leaving lifelong scars and disability. The disease, spread by sandflies, affects some of the poorest people on earth, according to WHO, and is associated with malnutrition and poor housing. Around 1 million new cases occur annually, causing 20,000 to 30,000 deaths. Leishmaniasis is climate-sensitive, affected by changes in rainfall, temperature and humidity ― which means it could be exacerbated by global warming. (credit:Corbis Documentary/Getty Images)
Trachoma(07 of18)
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Trachoma is an eye disease, which if untreated, can cause irreversible blindness. It causes visual impairment or blindness in 1.9 million people, per WHO. The disease is present in poor, rural areas of 42 countries in Africa, Latin America, Asia and the Middle East ― but Africa is the most affected. (credit:STR via Getty Images)
Rabies(08 of18)
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Rabies is almost always fatal once symptoms show up. Initial symptoms are fever and tingling around the wound. As the virus spreads, people with “furious” rabies become hyperactive and die by cardiac arrest; people with “paralytic” rabies become paralyzed, fall into a coma and die. Transmitted by pet dogs, rabies causes tens of thousands of deaths every year. The disease is present on all continents except Antarctica ― but more than 95 percent of human deaths due to it occur in Asia and Africa. It is a neglected disease primarily affecting poor populations, where vaccines are not readily available. (credit:NOAH SEELAM/AFP/Getty Images)
Leprosy(09 of18)
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Leprosy is a chronic disease, which when untreated can cause permanent damage to the skin, nerves, limbs and eyes. There were 176,176 cases at the end of 2015, according to WHO. While the stigma associated with the disease means people are less likely to seek treatment, leprosy is curable, and treatment early on can avoid disability. Leprosy was eliminated as a public health problem in 2000 ― meaning there is now less than one case for every 10,000 people worldwide. (credit:Chandan Khanna/AFP/Getty Images)
Schistosomiasis(10 of18)
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Schistosomiasis is a chronic disease that causes gradual damage to internal organs. Symptoms include blood in urine, and in severe cases, kidney or liver failure, and even bladder cancer. Around 20,000 people die from it each year. Transmitted by parasites in infested water, the disease largely affects poor, rural communities in Africa that lack access to safe drinking water and sanitation. “[People] get it as kids bathing in water,” Sandrine Martin, a staff member for the nonprofit Malaria Consortium in Mozambique, told HuffPost. “But the symptoms, like blood in the urine, only develop later ― and then people tend to hide it because it’s in the genital area.” (credit:Malaria Consortium)
Chikungunya(11 of18)
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Chikungunya is a disease that causes fever and severe joint pain, according to WHO. While it is rarely fatal, it can be debilitating. Since 2004, it has infected more than 2 million people in Asia and Africa. There is no cure for the disease, which is transmitted to humans by infected mosquitoes. The name comes from a word in the Kimakonde language, spoken in some areas of Mozambique and Tanzania, that means “to become contorted” ― a nod to the hunched-over position of people who are affected with joint pain. (credit:Universal Images Group/Getty Images)
Echinoccosis(12 of18)
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Echinoccosis is a parasitic disease that leads to cysts in the liver and lungs. While it can be life-threatening if untreated, even people who receive treatment often have a reduced quality of life, according to WHO. Found in every continent except Antarctica, the disease is acquired by consuming food or water contaminated with tapeworm eggs, or through direct contact with animals who carry it, such as domestic dogs or sheep. (credit:Smith Collection/Gado/Getty Images)
Foodborne Trematodiases(13 of18)
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Foodborne trematodiases can cause severe liver and lung disease, and on rare occasions death. Most prevalent in East Asia and South America, the disease is caused by worms that people get by eating raw fish, shellfish or vegetables that have been infected with larvae. While early, light infections can be asymptomatic, chronic infections are severe.More than 56 million people were infected with foodborne trematodes, and over 7,000 people died in 2005, the year of WHO’s most recent global estimate. (credit:Alexandre Tremblot de La Croix via Getty Images)
Buruli Ulcer(14 of18)
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Buruli ulcer is a skin infection caused by bacteria that often starts as a painless swelling, but without treatment, it can lead to permanent disfigurement and disability. In 2014, 2,200 new cases were reported, with most patients under age 15. The exact mode of transmission is still unknown. The majority of cases, if detected early enough, can be cured with antibiotics. (credit:ISSOUF SANOGO/AFP/Getty Images)
Yaws(15 of18)
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Yaws is a chronic, disfiguring childhood infectious disease. Affecting skin, bone and cartilage, the symptoms show up weeks to months after infection and include yellow lesions and bone swelling. More than 250,000 cases of yaws were reported from 2010 to 2013, WHO told HuffPost. A lack of clean water and soap for bathing contributes to its spread. Only 13 countries are known to still have cases of yaws, including Ghana, Papua New Guinea and Solomon Islands. (credit:BIOPHOTO ASSOCIATES via Getty Images)
Soil-Transmitted Helminth(16 of18)
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Soil-transmitted helminth infections are among the most common infections worldwide and affect the poorest communities. People are infected by worms transmitted by human feces contaminating soil in areas with poor sanitation. People with light infections usually have no symptoms. Heavier infections can cause diarrhea, abdominal pain, general weakness and impaired cognitive development. Depending on the number of worms, it can lead to death. Up to 2 billion people are infected worldwide, according to WHO. But because infections can be light, not all patients suffer, WHO’s Ashok Moo told HuffPost. (credit:Malaria Consortium)
Taeniasis(17 of18)
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Taeniasis is an intestinal infection caused by tapeworms, which mostly causes mild symptoms, such as abdominal pain, nausea, diarrhea or constipation. But if larvae infect the brain, causing neurocysticercosis, the disease can cause epileptic seizures and can be fatal. People get it by eating raw or undercooked infected pork. The ingested tapeworm eggs develop into larvae and migrate through the body. Taeniasis is underreported worldwide because it is hard to diagnose in areas with little access to health services, according to the CDC. (credit:Science Source/Getty Images)
Guinea Worm(18 of18)
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Guinea worm is a crippling disease that it is close to being eradicated. There were only 22 human cases reported in 2015, according to WHO ― down from around 3.5 million cases in 21 countries in the mid-1980s. The disease is usually transmitted when people with limited access to quality drinking water swallow stagnant water contaminated with parasites. About a year after infection, a painful blister forms ― most of the time on the lower leg ― and one or more worms emerge, along with a burning sensation. It is rarely fatal, but can debilitate infected people for weeks. The Carter Center, founded by former President Jimmy Carter and his wife, has been instrumental in efforts to eradicate the disease. (credit:PETER MARTELL/AFP/Getty Images)