Do you have high fever, shivering, severe joint pains (the joints of your hand and feet may be swollen and painful), a headache, red eyes and itchy skin lesions?

Ah, you probably have a viral fever. Dengue, perhaps? Certainly, patients with dengue display several of these symptoms. But consider another option — you also just might have chikungunya.

Chikungunya is not usually a fatal disease and goes away after a few days (or weeks, depending on the nutritional status of the person). Doctors treat only the symptoms, namely, high fever and joint pains.

Even so, chikungunya is ravaging India and has so far affected about 1.5 million people, though the fever has not taken a toll in terms of officially confirmed deaths. The worst hit in India is the south Indian state of Karnataka which reported more than 7.5 lakh suspected chikungunya cases.

According to the latest government of India statistics, chikungunya has affected as many as 137 districts in as many as 10 states and union territories in the country, including the Andaman and Nicobar Islands. This is almost a quarter of the Indian landmass, points out Dr P K Das, director of the Vector Control Research Centre in Pondicherry.

What is more, the current chikungunya outbreak is predominantly hitting rural areas. Traditionally, chikungunya, like dengue, has been an urban health problem. “There is nothing unusual about it. Rural areas in most states in southern and western India are not any longer rural in the traditional sense of the word,” notes Dr. P K Das, the director of the Vector Control Research Centre, in Pondicherry. Many villages in these states has become semi-urban in nature, thanks to economic development during the last several years. The disease gets its name from a language used by local tribes in Makonde plateau in Tanzania where the first case of chikungunya was reported in 1952. In Makonde language, chikungunya means “that which bends up,” which describes the stooped posture caused by the arthritic symptoms of the disease.

Still, the chikungunya epidemic may be more serious than what meets the eye. Indian medical scientists who mapped the viral strains of blood samples from close to 2,000 patients have established that it is genetically similar to the one that devastated several Indian Ocean countries. For instance, in the French-ruled Reunion Islands, located 200 km southwest of Mauritius in the Indian Ocean, the virus infected one-third of its 7,70,000 - strong population, killing about 238 people.

The outbreak

The study, by a team of scientists from the National Institute of Virology (NIV), Pune, said the current outbreak — first reported in October last year — was caused by an African genotype (the genetic make-up of an organism) which can be grouped with viral strains from Reunion Islands. Their study, scheduled to appear in the October 2006 issue of Emerging Infectious Diseases journal, says the viral strain is vastly different from the ones circulating in India. Though how the virus entered India still remains a mystery, it has been around in the country for five years, slowly chipping away at the immunity of Indians to the disease, they conclude.

But what could be more worrying for India is the findings of another study carried out by a team of French virologists. Their study on chikungunya viral strains isolated from Reunion Islands published in the July 2006 issue of Public Library of Science Medicine (PLoS) journal showed that the strains have been undergoing subtle changes in their genetic make-up so fast that the human immune system fails to catch up with them. This explains why there have been so many cases of chikungunya in the island since it broke out at the end of 2004. Till date, Reunion Islands reported about 2.7 lakh chikungunya cases.

According to French virologists at the Pasteur Institute in Paris and Lyon who mapped the genetic sequences of several chikungunya virus samples from patients in Reunion Islands and the Seychelles, though the outbreak began with a strain related to East African strains of the virus, it subsequently developed into several distinct variants. Chikungunya viral strains are broadly grouped into three distinct subgroups: the first one represents all strains in Asia, the second one the ones from western Africa and the third the other African strains.

Intriguingly, the French scientists spotted alterations in a particular gene called E1 in the chikungunya virus. These changes, missing in earlier strains but present in the recent versions, do away with the need for having cholesterol for proliferation, they hypothesise. A typical chikungunya virus, which uses mosquitoes for transmitting the disease to humans and other mammals, uses cholesterol in mosquitoes for multiplication. But the newly-emerged strains seem to have bypassed this mechanism. This evolutionary adaptation is part of the virus’ survival strategy, says Herbert Virgin, a scientist at the Washington University School of Medicine, who edited the work. Mosquitoes generally have very little cholesterol and this would have limited their rapid multiplication. But the downside of this could be that there would be a larger population of the virus available for human infection and hence it could lead to a rapid spread of the disease, as happened in Reunion Islands and neighbouring Madagascar.

This could be true of India too, if the pathogen doing the rounds is more close to the East African type than to the ones found in Asia, as the NIV study says. A study in 2000, by a team of researchers led by Ann M Powers from the University of Texas Medical Branch, happened to find that the chikungunya viral strains circulating in Asia have exhibited very little genetic changes despite being around for 35 years and were present in a vast geographical range. To some extend this may explain why chikungunya, first reported in 1963 in Calcutta, occurred frequently. The last recorded outbreak of chikungunya in the country, prior to the current one, was reported in Maharashtra and Karnataka in the early seventies.

Another theory forwarded is that as three decades have passed since the last outbreak, a large section of society has become susceptible to the chikungunya virus. “The virus may have been circulating all this while, but did not lead to an outbreak because of the inherent immunity of the people to the virus, thanks to earlier outbreaks,” argues Pradeep Seth, former head of virology at the All India Institute of Medical Sciences in New Delhi. Such diseases re-emerge as and when a susceptible population builds up in a society, observes Seth, who currently works as an independent consultant in virology and medical biotechnology.

Similar symptoms

Chikungunya is among the many mosquito-borne diseases to have assumed alarming proportions. Exactly 10 years ago, dengue haemorrhagic fever — significantly spread around by the same Aedes eagypti mosquitoes that transmit chikungunya — emerged as a major public health scare in India. Dengue, too, was a sporadically reported disease till October 1996. Aedes aegypti, which breeds in the rainy season, when freshwater pools are around, is a day-biting mosquito and feeds multiple people, unlike its anopheles counterparts that spread malaria.

To be sure, not all the 1.5 million cases reported since October last year may be chikungunya. This is because chikungunya’s clinical symptoms are quite similar to those of several other viral fevers. The chances of misdiagnosing other infections such as dengue as chikungunya are very high, experts say. NIV, which has tested 12,000 samples till date, could find only 10 per cent of the specimens positive to chikungunya.

Even so, experts are not discounting the magnitude of the problem. “I consider it is a serious public health issue, particularly it has resurfaced after a gap of 33 years,” says Dr Das. Moreover, cases are being reported from newer areas every day. For instance, in the first fortnight of September as many as 15,000 new cases were confirmed in Ahmedabad by city administration officials. “The epidemic is far from over,” NIV director Akhilesh C Mishra told KnowHow.

It is true that chikungunya viral infection is seldom fatal. But it incapacitates victims for days on end, resulting in the loss of several mandays. It is the poor who live on daily wages who tend to suffer the most. This is particularly true of this current outbreak too as it coincided with the kharif farming season.

In many of the worst-hit states like Andhra Pradesh and Karnataka the number of chikungunya cases is coming down. The number of chikungunya cases being reported was the highest during June and July last year. “Now it is on the decline,” reports Usha Ganesh, principal secretary, health and family welfare department, Karnataka. She adds: “As chikungunya is a self-limiting disease, there is no medication or vaccination. Prevention is the best cure.” Whatever medication offered is purely supportive and symptomatic such as treating fever with paracetomol or giving pain killers like diclofenac for relieving joint pains. Ganesh says the government has taken active measures to spray all larvae sites and prevent stagnation in water. “One day of the week has been declared a dry day in each district. All water containers are cleaned,” says Ganesh.

The on-going chikungunya epidemic underlines the gaps in disease surveillance and vector control strategies in the country. Says Seth, “We virologists have been crying from the rooftop for long to have a district-level sentinel disease surveillance system in the country. Without such a mechanism in place, it will very difficult for a country the size of India to monitor new pathogens with epidemic potential, let alone controlling them in the initial stages.”

Viral reach

Suspected number of cases

Karnataka • 7.5 lakh
Bijapur • 93,103
Bangalore rural • 83,871
Bhagalkote • 46,055
Gulbarga • 43,657
Dharwad • 36,437
Maharashtra • 3 lakh
Andhra Pradesh • 76,000
(Telangana)
Tamil Nadu • 65,000
Kerala • 50,000
Madhya Pradesh • 40,000
Gujarat • 25,000