NEW DELHI — An epidemic of dengue fever in India is fostering a growing sense of alarm even as government officials here have publicly refused to acknowledge the scope of a problem that experts say is threatening hundreds of millions of people, not just in India but around the world.
India has become the focal point for a mosquito-borne plague that is sweeping the globe. Reported in just a handful of countries in the 1950s, dengue (pronounced DEN-gay) is now endemic in half the world’s nations.
“The global dengue problem is far worse than most people know, and it keeps getting worse,” said Dr. Raman Velayudhan, the World Health Organization’s lead dengue coordinator.
The tropical disease, though life-threatening for a tiny fraction of those infected, can be extremely painful. Growing numbers of Western tourists are returning from warm-weather vacations with the disease, which has reached the shores of the United States and Europe. Last month, health officials in Miami announced a case of locally acquired dengue infection.
Here in India’s capital, where areas of standing water contribute to the epidemic’s growth, hospitals are overrun and feverish patients are sharing beds and languishing in hallways. At Kalawati Saran Hospital, a pediatric facility, a large crowd of relatives lay on mats and blankets under the shade of a huge banyan tree outside the hospital entrance recently.
Among them was Neelam, who said her two grandchildren were deathly ill inside. Eight-year-old Sneha got the disease first, followed by Tanya, 7, she said. The girls’ parents treated them at home but then Sneha’s temperature rose to 104 degrees, a rash spread across her legs and shoulders, and her pain grew unbearable.
“Sneha has been given five liters of blood,” said Neelam, who has one name. “It is terrible.”
Officials say that 30,002 people in India had been sickened with dengue fever through October, a 59 percent jump from the 18,860 recorded for all of 2011. But the real number of Indians who get dengue fever annually is in the millions, several experts said.
“I’d conservatively estimate that there are 37 million dengue infections occurring every year in India, and maybe 227,500 hospitalizations,” said Dr. Scott Halstead, a tropical disease expert focused on dengue research.
A senior Indian government health official, who agreed to speak about the matter only on the condition of anonymity, acknowledged that official figures represent a mere sliver of dengue’s actual toll. The government only counts cases of dengue that come from public hospitals and that have been confirmed by laboratories, the official said. Such a census, “which was deliberated at the highest levels,” is a small subset that is nonetheless informative and comparable from one year to the next, he said.
“There is no denying that the actual number of cases would be much, much higher,” the official said. “Our interest has not been to arrive at an exact figure.”
The problem with that policy, said Dr. Manish Kakkar, a specialist at the Public Health Foundation of India, is that India’s “massive underreporting of cases” has contributed to the disease’s spread. Experts from around the world said that India’s failure to construct an adequate dengue surveillance system has impeded awareness of the illness’s vast reach, discouraged efforts to clean up the sources of the disease and slowed the search for a vaccine.
“When you look at the number of reported cases India has, it’s a joke,” said Dr. Harold S. Margolis, chief of the dengue branch at the Centers for Disease Control and Prevention in Atlanta.
Neighboring Sri Lanka, for instance, reported nearly three times as many dengue cases as India through August, according to the World Health Organization, even though India’s population is 60 times larger.
Part of India’s problem is that some officials view reports of dengue infections as politically damaging. In September, Mamata Banerjee, the chief minister of West Bengal, dismissed reports of an increasing number of dengue-related deaths, saying doctors were misdiagnosing. “So everyone is earning a bad name,” she said at a news conference.
A central piece of evidence for those who contend that India suffers hundreds of times more dengue cases than the government acknowledges is a recent and as yet unpublished study of dengue infections in West Bengal that found about the same presence of dengue as in Thailand, where almost every child is infected by dengue at least once before adulthood.
“I would say that anybody over the age of 20 in India has been infected with dengue,” said Dr. Timothy Endy, chief of infectious disease at Upstate Medical University in Syracuse.
For those who arrive in India as adults, “you have a reasonable expectation of getting dengue after a few months,” said Dr. Joseph M. Vinetz, a professor at the University of California at San Diego. “If you stay for a longer period, it’s a certainty.”
The reason that such an extensive epidemic can hide in plain sight is that as many as 80 percent of dengue infections cause only mild symptoms of fatigue, said Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases. For many, the disease is experienced as “maybe just a fever that someone shrugs off.”
But the remaining 20 percent may be affected by more serious flulike symptoms, with high fever, vomiting, searing pain behind the eyes, skin rash, and muscle and joint aches that can be so intense that the illness has been dubbed “breakbone fever.”
The acute part of the illness generally passes within two weeks, but symptoms of fatigue and depression can linger for months. In about 1 percent of cases, dengue advances to a life-threatening cascade of immune responses known as hemorrhagic or shock dengue.
This potentially mortal condition generally happens only after a second dengue infection. There are four strains of the dengue virus, and infection with a second strain can fool the immune system, allowing the virus to replicate. When the body finally realizes its mistake, it floods the system with so many immune attackers that they are poisonous. Such patients must be provided intravenous fluids and round-the-clock care to avoid death.
Twenty years ago, just one of every 50 tourists who returned from the tropics with fever was infected by dengue; now, it is one in six, said Dr. Velayudhan, the W.H.O. official. The Portuguese archipelago of Madeira is in the midst of an epidemic.
On Oct. 9, Puerto Rico’s Health Department declared a dengue epidemic after at least six people died and nearly 5,000 people were sickened.
The great danger of having hundreds of millions of people in India with undiagnosed and unacknowledged primary infections is that a sudden shift in the circulating dengue strain could cause a widespread increase in life-threatening illnesses.
“We have been fortunate so far,” said Dr. Kakkar of the Indian public health group. “But if, God forbid, we come across that situation we probably need far better health-care management and inpatient care facilities.”
Trucks spewing pesticides against mosquitoes are now a regular presence in New Delhi neighborhoods, but rapid and disorderly urbanization — a hallmark of India’s development — increases the risks of dengue proliferation, so few believe the government here can do much to halt its spread.
The best hope for relief is a vaccine, but a recent trial of the most advanced vaccine candidate largely failed.
“I think we’re looking at 10 to 12 years before we see an effective vaccine, and that’s if we’re lucky,” Dr. Halstead said. “In the meantime, we’re in trouble.”
Hari Kumar contributed reporting.