State-run hospitals in New Delhi are overrun with feverish patients, municipal spokesman Y.S. Mann said.

"There is a sense of panic. People insist on hospitalization even if symptoms are mild," he said.

Still, the number of dengue cases recorded in Delhi are the highest in five years. At least 1,872 patients have tested positive for the illness this year so far, compared to 1,695 in 2010, Mann said. Seven of them have died in recent weeks.

Television footage showed patients sharing beds in government hospitals as New Delhi chief minister Arvind Kejriwal made surprise checks at crowded wards.

His inspections came after national media ran the story of a six-year-old boy who died from a suspected case of dengue fever. Several city hospitals, his father said, refused treatment to his child, citing a shortage of beds.

Last week, a seven-year-old boy also died for want of treatment. Unable to bear the loss, his parents killed themselves by jumping from the roof of their rented four-storeyed house, police said.

Authorities say they have ordered hundreds of more beds to accommodate the surge of patients in government hospitals, which provide free treatment. They also mandated private hospitals to not turn away anyone requiring admission.

Vastly under-reported

Nationally, India recorded 75,808 dengue fever cases in 2013 and 40,571 in 2014, according to the health ministry.

But independent researchers say the disease is vastly under-reported. According to a study by Brandeis University in Massachusetts last year, India had six million annual clinically diagnosed dengue fever cases between 2006 and 2012.

The study also pegged the cost of dengue fever treatment in India at $548 million per year.

Even without an outbreak, New Delhi's four major federal-funded hospitals are stretched by the thousands of patients that visit them everyday. The dozens of other state and municipal level hospitals in the city also suffer from overcrowding.

With an estimated 25 million inhabitants, Delhi is now ranked the world's second most populous city after Tokyo, according to a 2014 UN report.

Billions of dollars needed

Rapid urbanization is believed to have contributed significantly to population growth in the Indian capital, as more and more people migrate to cities in search of employment. India still has the world's largest rural population with 857 million followed by China with 635 million, the report says.

India's city planners estimate the nation will require an investment to more than $952 billion over the next two decades, from various domestic and foreign sources, to provide basic infrastructure in urban areas.

The South Asian nation currently spends one percent of its GDP on public health -- and Asia's third-largest economy fares poorly on multiple health indices.

The country has a high infant mortality and malnourishment rates, with around 50,000 mothers and 1.3 million newborns dying every year during or immediately after delivery, officials say. Widespread illiteracy, poverty, poor sanitation and nutrition have also been identified as contributors to disease.