Recent resurgence of Chikungunya fever in Delhi, India

This outbreak investigation in Palam area, Delhi during August to December, 2010 found approximately 71% to be serologically positive for Chikungunya virus by IgM Mac ELISA. There was no reported case of mortality, although morbidity was quite high. Majority (62.8%) of affected people belonged to 15-45 years of age group and most of them were females (62.7%). During this survey, it was observed that Chikungunya cases peaked during October (324 cases) than other months. Breeding places were mostly confined to water collection in plastic and metal containers, construction sites and coolers.

Chikungunya is a self-limiting viral infection usually characterized by sudden onset of high fever, skin rash and joint pain with or without swelling cause by an Arbo virus and is transmitted by Aedes mosquitoes (Aedesaegypti). ^[1] The incubation period of Chikungunya is usually between 2-10 days and mostly affects adult population in compare to young population. ^[2],[3],[4] In India first outbreak of Chikungunya was documented in Kolkata during 1963 and after that 4 to 5 outbreaks had occurred. ^[1] The last outbreak was reported in 1971 and after that no such outbreak occurred. ^[2] It was assumed that virus had vanished from this region. Surprisingly since December 2005, more than 1,80,000 cases of Chikungunya was detected in India which clearly indicates re-emergence of Chikungunya in India. ^[2],[3] Since then Chikungunya become a major public health problem in India. An estimate of prevalence of infection due to Chikungunya from several surveys conducted during an outbreak gives us an idea of burden of problem in a specific region which seems crucial for initiating any intervention strategy. ^[4]

Although, Chikungunya is self-limiting viral illness, some neurological complications like meningoencephalitis, demyelinating neuropathy, optic neuritis and myocarditis are not uncommon. ^[2],[3],[4] Till date, no specific treatment is available for this infection. Vector control through proper intervention is only mode of preventing this epidemic. It is evidenced from prior literature that most effective strategy for reducing density of Aedes mosquitoes is community-based intervention and personal protective measures. ^[4]

It is evident from prior survey that the main reason for this outbreak is lack of herd immunity, in-appropriate vector control strategy, emergence of rapid mutation of the virus. ^[2],[4] Another issue with such outbreak is non-availability of proper laboratory diagnosis. ^[1],[2] The reasons for outbreak for Chikungunya virus is unclear and yet to be explored. ^[2]

A study during 2006 among 140 patients attending Nizam’s Institute of Medical Sciences, Hyderabad found near about 50% of them to be positive for Chikungunya specific RNA by reverse transcription-polymerase chain reaction. ^[5] Theinvestigation of fever among 800 patients in Kolkata during 2007 showed nearly 41% was found to be reactive for Chikungunya. ^[6] It was also observed that 66% were male patients and most common symptoms among sero-positive cases were sudden onset of fever, joint pain and skin rashes. ^[6] It is quite clear from this study that there is re-emergence of Chikungunya epidemic in West Bengal after a gap of almost four decades. ^[6] Another Chikungunya outbreak investigation by Inamadar et al. among 145 cases attending tertiary care center in South India found all ages were affected, most common cutaneous manifestation was pigmentary changes (42%) and more males were affected in compare to females (1.8:1). ^[1]

Until recent resurgence Chikungunya was never a public health priority in India. Now it has become an important issue in domain of public health due to its rapid onset, its potential for epidemic and high morbidity. ^[7] From 2006, the disease spread to non-endemic areas in India mainly through travelers. ^[7] The economic impact of Chikungunya in India was much higher than estimated. During 2006 epidemic of Chikungunya, it was estimated that national burden in terms of DALYS (Disability Adjusted Life Years) was 25,588 ^[7] while 69% of DALYS was contributed by persistent arthalgia. ^[7]

Laboratory diagnosis of Chikungunya poses a great threat as most commonly practiced test like ELISA for detection of IgM antibodies is not standardized and interpretation of test results should be done with caution. ^[7] Diagnosis is usually done based on triad of clinical symptoms like sudden onset of fever, skin rash and arthalgia. ^[5],[6],[7]

As Chikungunya is self-limiting disease and treatment is mainly supportive. The best strategy for control of such outbreak is raising awareness of the community through mass education by public health officials. Vector control measures like spraying insecticides for example temephos, fenthion, malathion and DDT, clearing stored water and personal protective measures is also a key element in control of such outbreak. ^[8]

Research has shown that most important reservoir of vector of Chikungunya is in stored water in plastic or metal container and also available at construction sites. ^[2] During this present survey community received education regarding safe water storage practices and personal hygiene which seems important issues in control of such outbreak.

It is evident from prior studies and the present one that Chikungunya has become a major public health problem in India since 2006 and appropriate strategies should be initiated by public health specialist as well as health care personnel to halt this epidemic.

Source of Support: None, Conflict of Interest: None