Even as political parties continue the blame game for the spread of chikungunya in Delhi, experts are divided on whether they can attribute the death of 12 patients to the mosquito-borne viral disease. Some researchers even say there is a possibility that the chikungunya virus has become more potent and this may have triggered severe complications in the patients who died in Delhi hospitals while being treated for the infection.

This year, India has recorded 14,656 cases of chikungunya. Karnataka has the most cases followed by Maharashtra and Delhi, according to the National Vector Borne Disease Control Programme under the Union health ministry. But this is the first time in India that a city has recorded deaths attributed to chikungunya.

Delhi's health authorities seem ill-equipped to handle the situation. Health minister Satyendra Jain declared that the virus cannot cause death because that is what he read on Google. The World Health Organisation has, in fact, documented 191 deaths in different parts of the world that can be attributed to chikungunya.

Chikungunya is unlikely to kill a healthy person who has no other serious medical problems. Public health experts say that the virus does not cause death often but sets off debilitating symptoms that may affect patients even years after the onset of the disease. With hospitals in Delhi recording deaths attributable to chikungunya, there is an urgent need to study the “pathology of the virus” or the mechanism by which is causes disease, they said. But doctors are divided on whether chikungunya can be fatal.

Can chikungunya kill?

Health officials in Karnataka, a state that has recorded 66% of the chikungunya cases in the country since January this year, said they had never seen a chikungunya patient develop complications that could have a fatal outcome. “I am rather shocked that hospitals (in Delhi) are recording chikungunya deaths," said Dr Prakash Kumar, deputy director in Karnataka's health department. "We have had so many cases here but not a single death. It is a crippling disease and it does not exaggerate the pre-existing illness in a patient.”

A study published in Emerging Infectious Diseases in 2008 found an increased mortality rate during the chikungunya epidemic in Ahmedabad in 2006. The study’s lead author, Dr Dileep Mavalankar, studied the association between the chikungunya epidemic in India and the mortality rate in Ahmedabad then. “We found that 2,944 excess deaths occurred during the epidemic period when compared to the same months in the previous four years,” said Mavalankar.

Public health experts said that in the case of the 12 people who died in Delhi, chikungunya did increase their risk of dying. “Though it may not be a direct reason, it did contribute as a cause of death,” said a senior doctor from Delhi.

People suffering from dengue and chikungunya being treated at a Delhi hospital. Photo: IANS.
People suffering from dengue and chikungunya being treated at a Delhi hospital. Photo: IANS.

However, Dr Suranjeet Chatterjee from Indraprastha Apollo Hospital, who has treated over 100 cases of chikungunya, said it was incidental that the people who died were suffering from chikungunya. “It could be any other virus," he said. "It is just because we are actively testing patients for chikungunya in Delhi that we found they had chikungunya.”

Out of the 12 deaths, five were at Indraprastha Apollo Hospital. Chatterjee was not involved in their treatment.

Possible mutation?

According to the Indian Council of Medical Research, the chikungunya strain in circulation in India has not undergone any change since previous outbreaks. A senior official said the East Central South African strain continues to remain in circulation since 2006, when the country witnessed a major outbreak of the vector-borne infection. “There are no detailed studies about mutation but we know that there is always a risk of an increased outbreak potential as viruses like chikungunya keep on changing,” added the official.

But Dr Paluru Vijayachari from the Regional Medical Research Centre at Port Blair in the Andaman and Nicobar Islands suspects a change in the genetic content of the virus. “It is perhaps becoming more potent,” said Vijayachari, who has published several papers about the chikungunya epidemic in the islands. “We had reported instances where patients had developed acute flaccid paralysis – a complication not commonly reported among chikungunya patients.”

Causes of death

A statement by Indraprastha Apollo Hospital stated that of the five deceased, four were elderly patients with associated pre-existing chronic illnesses such as chronic kidney disease, diabetes mellitus, hypertension, coronary artery disease and old-age debility. In fact, the health authorities as well as the Delhi health minister have maintained that those suspected to have died of chikungunya actually died of other illnesses they were already suffering from. On Friday, Union Health Minister JP Nadda asked for a detailed report from the Delhi government on deaths due to dengue and chikungunya.

Disagreeing with the government’s attempt to downplay the role of chikungunya in these deaths, Dr Dileep Mavalankar said that the cause of death is identified as the disease that triggers a chain of events, which ultimately leads to a person’s death. “Blaming a pre-existing illness for someone’s death is not correct," he said. "Half of the population will have some co-morbidity. What we need to [ask] is that if chikungunya would have not happened, would the person have still died.”

When dengue causes confusion

The presence of active dengue and chikungunya transmission in the community could also be triggering severe complications in patients, said doctors. In Karnataka, out of the 4,000 people who tested positive for dengue recently, six were also suffering from chikungunya. “There is always a possibility that a patient may have been infected with both dengue and chikungunya,” said Dr Prakash Kumar from the state's health department. “Though chikungunya is non-fatal, dengue is, which could explain the rising mortality.”

The challenge, doctors said, is the possibility of false negative results of blood investigations. Many tests are available in the market and not all are reliable. Also, the test has to be done at a particular stage of the infection to get accurate results, said doctors. Rapid test kits to test for dengue can produce wrong results and are not considered reliable by the government.

Hence, doctors said, there was high possibility of a person not testing positive for a co-infection but actually suffering from it.

Is the virus adapting?

The National Vector Borne Disease Control Programme’s director Dr AC Dhariwal said the rainfall pattern in Delhi this year has led to an increase in the breeding of the Aedes aegypti mosquito, which can bear the dengue, chikungunya and even Zika viruses. “We are seeing more cases of chikungunya as the incubation period of the virus is as low as two days,” said Dhariwal. He added that Delhi had not seen an outbreak of chikungunya in the recent past and this made the population susceptible to the infection.

In 2010, Delhi had recorded 120 cases compared to 1,724 cases since January this year.

Infectious disease consultant in Mumbai, Dr Om Shrivastav, said the focus should be on understanding the interaction between the virus and the mosquito. “Despite all the vector control activities, the transmission of the virus is only increasing," he said. "Also it’s causing complications we didn’t see in the past, which only means that the mosquito is responding differently to the virus and causing the virus to change and adapt.”