Chikungunya Virus Infection in and Around Akola District, Maharashtra-Rising Trend Over a Decade

Introduction

Chikungunya (CHIK) is an arboviral infection that spreads by the bites of Aedes aegypti and Aedes albopictus. It is caused by the Chikungunya virus (CHIKV), which belongs to the family Togaviridae and the genus  Alphavirus. CHIKV is an enveloped, single-stranded, spherical RNA virus with a diameter of approximately 60-70 nm. The name ‘CHIK’ is derived from a word in the Makonde language meaning ‘that which bends up’, referring to the stooped posture caused by arthritis associated with the disease.¹

The disease was first recognized during an outbreak in southern Tanzania in 1952-53.² In India, a major epidemic of Chikungunya fever was first reported in 1963 in Kolkata, followed by outbreaks in 1965 in Pondicherry and Chennai (Tamil Nadu), Rajahmundry, Visakhapatnam, and Kakinada (Andhra Pradesh) Sagar (Madhya Pradesh) and Nagpur (Maharashtra).³ Another outbreak occurred in 1973 in Barsi, Maharashtra. Between 1983 and 2000, sporadic cases were recorded especially in Maharashtra state. The disease re-emerged in India again as an outbreak in 2005 after a quiescence of about three decades, affecting several states of India like Andhra Pradesh, Karnataka, Maharashtra, Tamil Nadu, and Madhya Pradesh.⁴

Clinically, the disease is diagnosed by a triad of fever, rash, and arthralgia. Arthralgia is sudden in onset, crippling, polyarticular, migratory, predominantly affecting the small joints of hands, wrists and feet, with lesser involvement of the larger joints.⁵ Maculo-papular rash may be seen typically over the face and trunk. The acute phase lasts for 2-3 days and may remit after a gap of 4-10 days, resulting in a "saddle back" fever curve. Symptoms like headache, nausea, vomiting, low back pain are also observed in many patients.

The disease needs to be differentiated from dengue (DENG) fever. Although rash appears in both the diseases, it is more common in DENG. Additionally, a decreased platelet count along with signs of haemorrhage strongly points toward a diagnosis of DENG.⁶ The probable diagnosis of CHIK can be made on the basis of clinical triad mentioned above and a confirmatory diagnosis can be achieved only by laboratory tests. 

The most sensitive serological test is the detection of Immunoglobulin M (IgM) antibodies using a capture enzyme-linked immunosorbent assay (ELISA), which also helps distinguish the disease from DENG. Confirmatory tests for CHIKV include detecting the viral RNA by Reverse transcriptase-polymerase chain reaction (RT-PCR).⁷

The present study provides preliminary data of CHIKV infection in and around Akola district through seropositivity of CHIKV infection in suspected patients of acute febrile illness, whose samples were received in the Department of Microbiology at a tertiary care hospital in Akola, over a period of ten years from January 2015 to April 2024. The seasonal trend and clinical manifestations of the infection were also analyzed during this period.

Materials and Methods

This hospital based retrospective study was carried out in the Department of Microbiology, at a tertiary care hospital in Akola, after approval from the Institutional Ethics committee. The study was conducted under National Vector Borne Disease Control Programme (NVBDCP) between January 2015 and April 2024. The study group comprised clinically suspected cases of CHIKV infection from hospital admissions, those who attended outpatient department (OPD) and various primary health centres across the districts of Akola, Amravati, Buldhana and Washim in Maharashtra, from January 2015 to December 2021 and from Akola and Washim between January 2015 and April 2024. Detailed history was obtained via a form provided by the Department of Health - Indian Council of Medical Research (DH-ICMR) virus research and diagnostic laboratory network.

Details such as age, sex, residential address, number of days of fever, type of joint involvement, any restriction in joint movements, morning stiffness in joints, and presence of any swelling were recorded. Five millilitre blood sample was collected and serum was separated as per standard guidelines.⁸ It was then tested for Chikungunya IgM antibodies using IgM antibody capture ELISA kit (NIV CHIK IgM) developed by National Institute of Virology, Pune, India. The test was performed as per the manufacturer’s instructions. Values were calculated and results were interpreted following the manufacturer’s guidelines.

Results

A total of 13,554 serum samples from suspected Chikungunya cases were received between January 2015 and April 2024. These were subjected to Chikungunya IgM antibody detection using MAC ELISA. Of these, 794 (5.86%) samples tested positive (Figure 1). The majority of positive cases were in the 21-30 year age group (23.8%), followed by the 11-20 year group (18.26%), and the 31-40 year group (17.25%), as shown in Table 1. Between January 2015 and April 2024, the highest number of Chikungunya IgM antibody ELISA positive cases were reported annually in October (27.95%), followed by November (14.23%), and September (13.72%), as depicted in Figure 2. The highest number of suspected as well as positive cases were predominantly found in the rural areas. Over the decade, an increasing trend in Chikungunya positivity was observed, with the exception of the years 2020 and 2021 (Figure 3 &Table 2). The common presenting features among Chikungunya IgM ELISA positive cases were fever, followed by myalgia, arthralgia, headache, and rash, as shown in Table 3.

Discussion

Chikungunya re-emerged in India as an outbreak in 2005 after a quiescence of about three decades. Since then, Chikungunya cases have been occurring both in sporadic and outbreak forms in various regions of India, including Maharashtra state. To assess the burden of Chikungunya in the Western Vidarbha region, we present the seroprevalence of cases in and around Akola district over a decade, from January 2015 to April 2024.

A total of 13,554 samples suspected of Chikungunya were received between January 2015 and April 2024 from Akola district and surrounding areas at the Microbiology laboratory of a tertiary care hospital in Akola. Of these, 794 cases tested positive by Chikungunya IgM antibody ELISA. Hence, the seroprevalence over this decade was found to be 5.86%. In comparison, Patil et al.,from Kasegaon, Maharashtra reported a seropositivity of 9.6%, while Krishna et al., from Telangana reported a prevalence of 10.34%. Singh et al., from Nagpur, Central India, observed a seropositivity of 16.99% in their study.^9,10,11

In this study, majority of the positive cases belonged to the age group 21-30 years (23.8%), followed by 11- 20 years (18.26%), and 31-40 years (17.25%). This is consistent with the findings of Suryawanshi et al., form Nagpur and Naik et al., from Karnataka, where the majority of positive cases belonged to the 16-30 year age group. However, this finding contradicts the report by Chandra et al., from Mangalore, who identified 31- 45 year age group as the most commonly affected. In our study, the higher positivity in the 21-30 year age group may be attributed to the fact that individuals in this age range are more likely to be outdoors for work or education. Since the vector, Aedes aegypti, has a daytime biting habit, this age group is more frequently exposed and therefore commonly affected.^12,13,14

In the present study, females (53.65%) were found to be more affected than males (46.35%). This finding is consistent with the studies by Baveja et al., from Mumbai, Sakhiya et al., from Ahmedabad and Singh et al., from Nagpur. In contrast, studies by Patil et al., from Kasegaon, Maharashtra, and Naik et al., from Karnataka, reported a male preponderance. There may not be a definitive reason for this variation, as seropositivity in either sex could depend on factors such as occupation, outdoor activity, and familial or societal roles, which influence the risk of exposure and consequently the outcome.^{15,16,11,9,13}

According to our observations, the most commonly affected period of the year was October, followed by November and September, consistently throughout the decade. These findings align with the study by Mahapatra from Delhi, that reported peak cases in October. Similarly, Baveja et al., from Mumbai and Mehta et al., from North India reported the highest number of cases between September and November. As the monsoon and especially the post-monsoon period provides favourable breeding conditions for both Aedes aegypti and Aedes albopictus, the majority of Chikungunya cases occur during this time, although sporadic cases and positivity are observed throughout the year.^17,18,15

The majority of the suspected (57.08%) as well as confirmed positive (55.92%) cases in this study were from rural areas of the districts mentioned above. These findings are consistent with Singh et al., from Nagpur who reported higher seroprevalence in rural areas.¹¹

One of the notable findings in our study is the rising trend of Chikungunya positivity in and around Akola district over the past decade. Except for the years 2020 and 2021, a steady rise in the number of positive cases in and around the district was observed. The decline during 2020-21 may be attributed to the COVID-19 pandemic, which likely led to underdiagnosis due to disrupted healthcare services and reduced case reporting.

There is a need for clinically differentiating Chikungunya from Dengue fever. Absence of haemorrhagic manifestations is one of the key features. In this study, all positive cases presented with fever and joint pain. Headache was reported in 94.45% of patients, while body pain was observed in 85.01%. These findings are consistent with the reports of Galate et al., from Mumbai and Kawle et al., from Chandrapur.^19,20

Chikungunya is a self-limiting febrile illness, with most patients requiring only palliative treatment. However, studies have reported long-term complications, including arthritis persisting for more than six months and various neurological manifestations. Public health awareness campaigns, source reduction of mosquitoes, education initiatives by paramedical staff, promotion of personal protection measures, and vigilant laboratory testing of suspected cases remain crucial and much needed.

Conclusion

Our study highlights the rising seropositivity of Chikungunya over the past decade in and around the Akola district. This emphasizes the need of regular surveillance, prompt laboratory testing of suspected cases to reduce disease burden and prevent acute neurological complications in severe cases. To avert any impending outbreaks, efforts must be taken at both individual and community levels through an integrated vector management approach. Engaging the private sector and strengthening referral services will further aid in curbing seasonal infections and address the underreporting of cases.

Source of Funding

 National Vector Borne Disease Control Programme (NVBDCP)

Source of Support

NIV Pune

Conflict of interest

Nil