In recent weeks, what is fast looking like an epidemic of dengue fever has been spreading in different parts of India. Delhi is over 600 reported cases, with 16 fatalities; Kerala has over 700 cases; Gujarat, 200; West Bengal, 300. At India’s top hospital, the All India Institute of Medical Sciences (AIIMS), one medical student has died and 20 nurses are infected. In today’s news, it appears that two of the grandsons of Prime Minister Manmohan Singh have also contracted the disease and have been admitted to the hospital.

Dengue fever, you ask?

Here’s the scoop. It’s transmitted by mosquitoes: not the Anopheles, which carries malaria, but the Aedes — especially the Aedes aegypti, which the Centers for Disease Control (CDC) describe as a “domestic, day-biting mosquito that prefers to feed on humans.” There are two strains of dengue. Regular dengue fever (DF) produces fever, headache, back ache, joint pains, nausea, eye pain and rash. Dengue hemorragic fever (DHF) is nastier and potentially deadly:

Dengue hemorrhagic fever is characterized by a fever that lasts from 2 to 7 days, with general signs and symptoms that could occur with many other illnesses (e.g., nausea, vomiting, abdominal pain, and headache). This stage is followed by hemorrhagic manifestations, tendency to bruise easily or other types of skin hemorrhages, bleeding nose or gums, and possibly internal bleeding. The smallest blood vessels (capillaries) become excessively permeable (“leaky”), allowing the fluid component to escape from the blood vessels. This may lead to failure of the circulatory system and shock, followed by death, if circulatory failure is not corrected.

There is no vaccine and no specific medication for dengue. Cases of DHF in particular require rapid hospitalization and fluid replacement therapy for the patient to pull through. This requires, obviously, a medical infrastructure that permits rapid hospitalization, not to mention hygienic hospital conditions, never a given anywhere in the world.

Mosquitoes are the only vector of the disease, meaning that anyone who contracts it in a hospital environment likely did so from mosquitoes hanging out there. The best way to prevent dengue, therefore, is to reduce mosquito breeding opportunities and infestation settings like standing water. In the immediate, the authorities in Delhi (and presumably other places as well) are carrying out a fumigation campagn with pesticides. At the same time, it seems that the country was also insufficiently prepared to deal with a disease that has been endemic for a long time.

The spread of dengue — as well as chikungunya, which has now killed 71 people in Kerala — comes at a time when health experts are revising their longtime opposition to DDT. The WHO has lifted its ban on DDT, and the US government also supports wider use of the once-dreaded chemical. This is controversial, obviously; this article, for example, makes the opposing case.

Dengue has been spreading worldwide as the Aedes mosquito makes itself at home in more and more places. Here is a map that shows the reinfestation of Aedes in the Americas since 1970. As a side note, there is also a hip band out of Los Angeles called Dengue Fever. They play a blend of psychedelic rock and Cambodian pop.