Infographic: What is dengue and how does it spread?

Tens of thousands of people across India, Pakistan and Bangladesh have been struck by dengue fever this year in one of the worst outbreaks in recent times that has further burdened the countries’ already fragile public health systems.

In India, at least 116,991 dengue cases have been reported this year, according to local media citing health officials. A total of 15 states and federally ruled territories have reported cases this year, accounting for 86 percent of India’s total dengue caseload till October 31.

In Pakistan, the two provinces that share a border with India – Punjab and Sindh – are also witnessing outbreaks. As of November 8, Punjab had recorded 19,021 dengue cases and 75 deaths this year, while Sindh recorded 4,273 cases, according to Pakistani officials. The total number of cases throughout the country is not known, but according to the International Federation of Red Cross and Red Crescent Societies [PDF], the capital Islamabad had an upward trend of continuously rising dengue cases.

And in Bangladesh, nearly 25,000 patients have been admitted to hospitals nationwide and 95 people died since January, according to the Directorate General of Health Services (DGHS). At least 151 new patients were hospitalised with dengue fever during the past 24 hours.

Dengue is a mosquito-borne viral infection primarily found in tropical climates where high temperature, humidity and unplanned rapid urbanisation create ideal conditions for infected mosquitoes to spread the dengue virus or DENV.

These mosquitoes usually live in places at an altitude below 2,000 metres (6,500 feet) and require temperatures of above 16 degrees Celsius (60 degrees Fahrenheit) to breed.

According to the World Health Organization (WHO), almost half of the world’s population, about four billion people, live in areas with a risk of dengue. Every year, 100-400 million people are infected with dengue and 40,000 people die of severe dengue.

Dengue virus transmission

Dengue cannot be spread directly from one person to another. Rather, the virus is spread through the bite of an infected female Aedes aegypti mosquito.

When an uninfected mosquito bites a person who has the virus in their bloodstream, the mosquito becomes infected. An infected mosquito can then transmit that virus to a healthy person by biting them, thus creating a cycle.

Infected mosquitoes can continue transmitting the virus to healthy people for their entire life span which generally lasts three to four weeks.

According to the WHO, the global spread of dengue has increased immensely in recent decades and is regarded as one of the 17 neglected tropical diseases (NTDs).

Symptoms

It typically takes four to five days after being infected for a person to develop symptoms, which can last for a week or longer.

About one in four people infected with dengue will get sick. For those, symptoms can range from headaches, nausea and fever to more severe ones such as severe abdominal pain, breathing difficulties and internal bleeding. About one in 20 people who get sick will develop severe dengue, which can be life-threatening, according to the Centers for Disease Control and Prevention.

Prevention and treatment

Preventing mosquito bites is among the best defences against dengue. This includes putting mosquito nets around beds, removing stagnant water at home, and using mosquito repellent.

There is no specific medication to treat dengue. Those who become infected are encouraged to rest, drink plenty of fluids and take pain relievers such as paracetamol (also known as acetaminophen) to control fever. Aspirin or ibuprofen should not be taken as they can increase the risk of bleeding complications.