• Bihar has recorded more than 15,000 dengue cases with 59 deaths so far this year, according to the official records.
  • These are the highest numbers of reported dengue cases and deaths in the state in at least five years there has been an increase of 608% in the number of cases between 2018 and 2023.

Why have dengue cases and deaths soared in Bihar?

  • The primary reason for the rise in dengue cases and deaths in Bihar is the delayed monsoon season, which usually lasts till mid-September but this year continued till mid-October.
  • Erratic rainfall led to the creation of shallow, stagnant pools of water, especially in densely populated areas of Patna, in which mosquitoes thrived.
  • Moreover, with winters yet to arrive, people have continued to use water coolers that are also a breeding ground for mosquitoes, according to the doctors.
  • The rise in cases has come on the back of a lack of sanitation and proper defogging by the state’s municipal corporations.

Have doctors witnessed any new dengue symptoms?

  • For the first time, doctors have witnessed liver and lung infections caused by dengue among the patients.
  • Doctors have also noticed that the patients are experiencing a recurrence of fever after 2-3 hours instead of the usual 6-8 hours.
  • Some patients have suffered from body itching and swelling in their liver.

Is there a rise in demand for platelets in Bihar?

  • For the last 10 days, the demand has grown substantially in Patna.
  • According to the standard protocol, patients receive platelets only after their count drops to 15,000 in number — a normal platelet count ranges from 150,000 to 450,000 per microliter of blood.
  • However, doctors have been injecting platelets even when the count is around 25,000 as a precautionary measure due to the high dengue death toll this season.

About Dengue:

  • Dengue is a viral infection caused by the dengue virus (DENV), transmitted to humans through the bite of infected mosquitoes.
  • About half of the world’s population is now at risk of dengue with an estimated 100–400 million infections occurring each year.
  • Dengue is found in tropical and sub-tropical climates worldwide, mostly in urban and semi-urban areas.
  • While many DENV infections are asymptomatic or produce only mild illness, DENV can occasionally cause more severe cases, and even death.


  • Most people with dengue have mild or no symptoms and will get better in 1–2 weeks. Rarely, dengue can be severe and lead to death.
  • If symptoms occur, they usually begin 4–10 days after infection and last for 2–7 days.

Symptoms may include:

  • high fever (40°C/104°F)
  • severe headache
  • pain behind the eyes
  • muscle and joint pains
  • nausea
  • vomiting
  • swollen glands
  • rashes
  • Individuals who are infected for the second time are at greater risk of severe dengue.

Severe dengue symptoms often come after the fever has gone away:

  • severe abdominal pain
  • persistent vomiting
  • rapid breathing
  • bleeding gums or nose
  • fatigue
  • restlessness
  • blood in vomit or stool
  • being very thirsty
  • pale and cold skin
  • feeling weak
  • People with these severe symptoms should get care right away.
  • After recovery, people who have had dengue may feel tired for several weeks.


Transmission through the mosquito bite:

  • The virus is transmitted to humans through the bites of infected female mosquitoes, primarily the Aedes aegypti
  • Other species within the Aedes genus can also act as vectors, but their contribution is secondary to Aedes aegypti.

Human-to-mosquito transmission:

  • Mosquitoes can become infected by people who are viremic with DENV.
  • This can be someone who has a symptomatic dengue infection, someone who is yet to have a symptomatic infection (they are pre-symptomatic), but also people who show no signs of illness as well (they are asymptomatic).
  • Human-to-mosquito transmission can occur up to 2 days before someone shows symptoms of the illness, and up to 2 days after the fever has resolved.

Maternal transmission:

  • The primary mode of transmission of DENV between humans involves mosquito vectors.
  • There is evidence however, of the possibility of maternal transmission (from a pregnant mother to her baby).
  • At the same time, vertical transmission rates appear low, with the risk of vertical transmission seemingly linked to the timing of the dengue infection during the pregnancy.
  • When a mother does have a DENV infection when she is pregnant, babies may suffer from pre-term birth, low birth-weight, and fetal distress.

Other transmission modes:

  • Rare cases of transmission via blood products, organ donation and transfusions have been recorded.
  • Similarly, trans-ovarial transmission of the virus within mosquitoes have also been recorded.

Syllabus: Prelims