To begin with, what is chikungunya?
It is a mosquito-borne viral infection that causes fever, rashes and arthralgia or joint pain. The causative organism, chikungunya virus (CHIKV), is transmitted in humans by the Aedes aegypti and Aedes albopictus mosquito species. The mosquito bites in daytime, and carries the infection from an infected to an uninfected person. Infected persons cannot spread the infection directly — which means the disease is not contagious. The name Chikungunya is derived from the Makonde (language of the ethnic people living in southern Tanzania and northern Mozambique) word meaning “that which bends” in reference to the stooped posture developed as a result of arthritic symptoms.
Where did CHIKV come from?
There is evidence that the virus originated in Africa and moved to Asia. The first outbreak was in 1952 in south Tanzania; there have been outbreaks in various parts of Africa since then. The first Asian outbreak was in 1958 in Bangkok; there have been outbreaks in Cambodia, Vietnam, Laos, Myanmar, Malaysia and Indonesia since. The most recent epidemic re-emergence was reported in 1999-2000 in Kinshasa where an estimated 50,000 were infected.
Is there any cure for the disease? What are the clinical features of infection?
There’s no cure. Treatment is focused on relieving symptoms like fever, muscle pain, headache, nausea, fatigue and rash. The infection is of acute onset. Symptoms generally develop after an incubation period of 4 to 7 days and, in most cases, disappear after 5 to 7 days even without treatment. In rare cases, symptoms may persist for longer, and complications may develop occasionally. A clinical triad of ‘fever, rashes and arthralgia’ is characteristic of chikungunya fever. Clinical features vary from high fever (more than 40 degrees Celsius), severe headache, chills and rigours, nausea and vomiting.
When did the virus hit India? When was the last outbreak in the country?
The first epidemic was reported in 1963 in Kolkata, followed by Chennai in 1965, and Barshi, Maharashtra, in 1973. The last epidemic outbreak took place in 2006. According to official estimates, more than 1.39 million suspected cases of the viral fever were reported, affecting 210 districts. The maximum number of cases were reported from Andhra Pradesh, Karnataka, Kerala, Tamil Nadu, Gujarat, Madhya Pradesh and Maharashtra. Migrations of people in the Indian Ocean region was seen as the main reason for the 2006 outbreak — the CHIKV genotype was found to be of the Eastern Central Southern African type, different from those of the 1960s and 1970s outbreaks, which saw Asian genotypes.
Can chikungunya cause death?
Mortality rate is very low, and serious complications are not common — however, in older people, the disease may contribute to the cause of death. Most patients recover fully, even though the joint pain may persist for several months and, in some cases, years. In a few cases, eye, neurological and heart complications, and gastrointestinal complaints, have been reported. The infection may go unrecognised if symptoms are mild, or may be misdiagnosed in areas where dengue too occurs.
What is the position this year in Delhi?
The official number is 20 cases, but doctors say there are more chikungunya cases than dengue this year. In private hospitals, doctors claim at least 50% of OPD patients have symptoms, and a few of them have tested positive. According to the Department of Microbiology at AIIMS, 712 samples were tested at its lab this year, of which 391 tested positive — 362 of the positive cases were tested between July 1 and August 20. Last year, only 64 cases were reported in Delhi.
So, why have the numbers gone up? And why is there a discrepancy in numbers?
Chikungunya is not a notifiable disease. Hence it is not binding that all numbers be reported to the concerned authority. The civic bodies compile separate figures for patients belonging to Delhi and those coming from outside — which is a significant number.
Doctors say that since the incubation period of the viral infection is small, the spread is more. Also, they say, the virus is evolving, and there could be new strain, or changes in the virus’s genome could be making it more virulent. Factors such as crowding and migration may have bought in new strains.
What are the similarities and differences between chikungunya and dengue?
The vector is the same and symptoms near identical. Clinical diagnosis is needed to differentiate between the two. Tests can detect the dengue virus or chikungunya virus in the blood in the first few days of infection, or antibodies against the viruses subsequently.