The study population

The patients who attended The Civil Hospital, Rajkot, India, the primary health care centres and the community health care centres which were covered under the district Rajkot, who presented with the sign and symptoms of fever, headache and joint pain which were suggestive of the acute Chikungunya infection were included in this study.

The case definition and the criteria for inclusion in the study

The patients with one or more of the following characteristics were included in the study:

The study sample

All the 193 eligible serum samples of the suspected cases of the Chikungunya patients who attended the outdoor and indoor patients departments at a tertiary care hospital in Rajkot and the primary health care centres, the community health care centres and the urban health centres which were covered under Rajkot district, which were collected during the one year study period which extended from 1^st January 2011 to 25^th December 2011, were processed and tested for the detection of the Chikungunya IgM antibody by using a solid phase, capture micro well ELISA technology (National Institute of Virology-Pune).

Data Collection

A specially designed, semi-structured questionnaire form was used to collect the data on the demographic factors like age, sex, and residence, in addition to the data on the history of the illness, the possible risk factors and the results of the investigations.

Blood samples (5-8 ml) were drawn from all the patients as a part of the routine laboratory work and the sera were separated and obtained for the processing for the Chikungunya IgM ELISA. These patients belonged to different localities of Rajkot.

Ethical Considerations

The data which were collected for the purpose of the current research were a part of the diagnostic technique. So an ethical consideration was not needed. While the patients with the suspected Chikungunya infection were dealt with, the patients' privacies were secured and the identifying information was kept confidential. A prompt treatment was provided for all the study subjects.

Out of the total 193 cases, 84 were positive for the Chikungunya IgM antibody. Out of the total 84 positive cases, 32 were males (38.09%) and 52 were females (61.9%). A high prevalence was seen in female patients. The age group which was most commonly affected in this study was the 40-50 years age group, with 34 (40.4%) cases occurring in this age group. Only 20(23.81%) cases occurred in the 20-30 years age group.

Among the total 84 positive cases, a majority of the patients presented with the triad of fever, headache and joint pain. There were 44(52.38%) cases with fever, headache and joint pain; while 15(17.85%) cases presented with fever, 7(8.33%) cases presented with joint pain, 3(3.57%) cases presented with GIT and vomiting symptoms, 2(2.38%) cases presented with rashes, 3(3.57%) cases presented with haemorrhage and 5(5.95%) cases presented with retro orbital pain. The Chikungunya infection shows seasonal variations in the month of November and December. There is an increased breeding of the Aedes mosquito in the post monsoon season.

Chuikungunya is a re-emerging debilitating infection. The name itself indicates the degree of the discomfort which is caused. 'Chikungunya', in Makonde means, 'that which bends up' or 'to dry up or become contorted'. Chikungunya Virus was first detected in 1963 in West Bengal [7]. This was followed by several epidemics in Chennai, Pondicherry, Vellore, Visakhapatnam, Rajmundry, Kakinada, Nagpur and Barsi between 1964 and 1973 [8]. These outbreaks have even inspired the writing of songs about the virus and the recognition of 'Keelamma the Chikungunya goddess'[9]. Over ten thousand cases have been reported. It has been suspected that many cases of Chikungunya either go misdiagnosed or unreported [10].

The phylogenetic analysis of the E1 gene of Chikungunya Virus indicates only three lineages with distinct genotypic and antigenic characteristics i.e. the "central/east African genotype [11], the "Asian genotype" [12] and the "west African genotype [13]. Additionally, a mutation at the 226 amino-acid (Valine-Alanine) of the E1 gene was observed during the recent outbreaks and it has been associated with the more efficient replication of Chikungunya Virus in Aedes albopictus [14]. Chikungunya Virus of the latest outbreak displayed the ECSA lineage, due to the accumulation of mutations in the viral genome, which has led to the appearance of new subgroups and has suggested a dynamic evolution of the virus [15].

Gender and age comparison:

When the Chi-square test was applied: Chi-square was 8.803, DF was 1 and the p value was 0.0030 [16]. In the present study, more females were affected, with a F:M ratio of 1.62:1. More number of cases occurred in the age group of 40-50 years [Table/Fig-1], which was comparable with the occurrences in other studies like those which were done on the Kerala outbreak [17], in which females were affected 194 (54.8%) more than the males. In the 2005-2006 Reunion Island and Indian Ocean outbreak [18] more males were affected, with a M:F ratio of 1.24:1, with the 58 years age group being mostly affected.

Comparing the signs and symptoms with those of other studies

In other studies, the common presenting symptoms were only fever and joint pain, followed by vomiting and rashes [18, 19]. In the present study, more patients had the triad of fever, headache and joint pain, which showed that headache may be the presenting symptom with fever and joint pain. Rash was seen only in very few patients [Table/Fig-2].

Comparison of the seasons of occurrence

In the present study, the Chikunguny cases occurred in the months of November and December, because in the post monsoon season, there is water accumulation. This artificial water collection is the source of breeding of the Aedes mosquito and the increased frequency of mosquito bites. The lack of awareness amongst the general public and the improper sanitation cannot be ignored. In other studies, most of the cases occurred between March to April, thus showing a seasonal variation [17, 18] [Table/Fig-3].

Whether or not the virus moves to the new world, it is still a significant burden on the already overstretched hospitals, health systems and communities of the affected regions. An economic pressure is created on the state and national laboratories due to the outbreak and on the local businesses due to the absenteeism from work for weeks due to the incapacitating symptoms.

[Table/Fig-4] shows the suspected cases of Chikungunya in various states in 2006 [19, 20].

The sex prevalence of Chikungunya is more in females. It is seen more in the 40-50 years age group. Among the total symptomatic cases, the more common symptoms which are observed are fever, headache and joint pain. In the present study, Chikungunya occurred more in the winter season, in the months of November and December. This study emphasizes the need for a continuous surveillance on the disease burden and for laboratory research which is aimed at the development of vaccine candidates, antiviral strategies and diagnostic kits. To reach these goals, several investigations for characterizing Chikungunya Virus can be done by doing murine studies to investigate the cell tropism and the neurovirulence determinants, transmissibility studies in mosquitoes by using chimeric viruses, and virulence/pathogenesis studies which can investigate the outcomes of the Chikungunya Virus strain variations (A. M. Powers, C. H. Logue, J. P. Ledermann, B. J. Sheahan and G. J. Atkins, unpublished results). Hopefully, these efforts will lead to advances in the public health capacity for the prevention of future arboviral outbreaks, combined with a rapid control of the outbreaks that occur.