|Year : 2014 | Volume
| Issue : 2 | Page : 47-49
Epidemiology of H1N1 in western Rajasthan
Mahendra Singh1, Prashant Babaji2, Nitin Sharma2, Subash Chandra3
1 Department of Community Medicine, AIIMS Medical College, Jodhpur, Rajasthan, India
2 Department of Pedodontics, Vyas Dental College, Jodhpur, Rajasthan, India
3 Department of Conservative Dentistry, Vyas Dental College, Jodhpur, Rajasthan, India
|Date of Web Publication||13-Jun-2014|
Department of Pedodontics, Vyas Dental College, Jodhpur, Rajasthan
Background: H1N1 pandemic posed a serious threat to world health community. We described the epidemiology of H1N1 in western Rajasthan. Materials and Methods: This study was a retrospective descriptive analysis all 686 confirmed cases of H1N1 in western Rajasthan from the month of August 2009 to March 2010 and conducted in hospitals attached to Dr. S. N. Medical College, Jodhpur. Data were analyzed using GraphPad software (GraphPad Prism ® .) and Chi-square test. Results: A total of 686 cases were confirmed positive with positivity ratio of 32.3%. The overall case fatality rate was 11.7%. The highest number of cases (50.7%) and deaths (60%) were seen during the month of Decemberand among the age group of 16-30 years. About 54% of patients were males. Mortality rate was higher in females (64%). Although, there were more cases reported from the urban area (60%), the mortality was higher in patients of the rural area (62.5%). The mortality rate among pregnant women was also higher than other groups. Conclusions: H1N1 influenza occurred predominantly among the younger age group with high case fatality especially among postpartum women in the study population
Keywords: H1N1, epidemiology case fatality
|How to cite this article:|
Singh M, Babaji P, Sharma N, Chandra S. Epidemiology of H1N1 in western Rajasthan. Sahel Med J 2014;17:47-9
| Introduction|| |
H1N1 is a novel strain of influenza A virus that evolved recently by genetic assortment. Following its emergence in March 2009 in Mexico, H1N1 virus spread rapidly throughout the world. WHO declared it as a pandemic on June 11, 2009.  The disease started in India in the month of May 2009 and the first laboratory confirmed case was reported from Hyderabad on 16 May.  The state of Rajasthan, which is the largest state in India reported its first case on July 23, 2009.  This study describes the epidemiological trends of H1N1 in Western Rajasthan.
| Materials and methods|| |
This hospital-based descriptive retrospective study was conducted in hospitals attached to Dr. S. N. Medical College, Jodhpur from month of August 2009 to March 2010. A pre-tested semi-structured questionnaire was used for the collection of data of all the patients visiting swine flu outpatient departments (OPDs), swine flu wards and the screening center in the college. The record was kept on a daily basis from the month of August. Each patient visiting either swine flu OPD or swine flu ward, suspected clinically to be H1N1 positive were grouped into three categories A, B and C according to the guidelines provided by Ministry of Health and Family Welfare Government of India in August, 2009. According to guidelines of India (2009), Category-A are patients with mild fever plus cough/sore throat with or without body ache, headache, diarrhea and vomiting. They do not require H1N1 testing or oseltamivir. They were monitored, for 24-48 h and confined at home. Category-B (i) in addition to all the signs and symptoms mentioned under Category-A, the patients had high grade fever and severe sore throat, may require home isolation and oseltamivir; (ii) in addition to all the signs and symptoms mentioned under Category-A, individuals having one or more of the following high risk conditions and were treated with oseltamivir: Children with mild illness but with predisposing risk factors. Pregnant women; persons aged 65 years or older; and patients with lung diseases, heart disease, and liver disease. Those falling in Category-C, as per the guidelines were confirmed by the real-time reverse-transcriptase-polymerase chain reaction (RT-PCR) in WHO reference laboratory by using throat and nasopharyngeal swabs and were included in the study.  Only atients who fell in Category-C were subjected to RT-PCR, while Category-B and Category-A individuals were empirically given oseltamivir and azithromycin, respectively, and were not included in the study. Data were analyzed using statistical GraphPad software (GraphPad Prism ® ). 
| Results|| |
Flu-like illness was reported by 10,608 patients, but testing for H1N1 using real-time reverse-transcriptase-polymerase chain reaction (RT-PCR) assay was done in only those 2121 (20%) patients. The number of individuals suspected as H1N1 peaked during the months of November-February with the maximum number of suspected 812 (38%) and confirmed 689 (32.34%) cases during study periodThe maximum case positivity was seen during the month of November [Table 1].
177 (25.87%) and 87 (12.71%) cases were seen in the age group ≤15 years and >45 years. respectively. On thw whole, more cases were seen in males (372 cases, 54%) compared to females (314, 46%). Specifically males were more affected than females in the age groups of 0-15 years and 46-60 years. The distribution of cases were almost equal for both sexes in other age groups [Table 2].
There were more cases in the urban (414, 60%) compared to the rural area (272, 40%). Of the 686 total positive cases, 80 died giving a case fatality rate of 11.7%. Most of the deaths (42%) were within 1-3 days of admission. Case fatality rate was significantly higher among patients in the rural (18.38%) compared to the urban area (7.24%).
Overall, the maximum case fatality rate of 13.79% was recorded in the month of December [Table 3]. The highest case fatality (12.75%) was seen in the age group (16-30 years) [Table 4]. Case fatality (63.8%) was higher in females than males (36.3%).
| Discussion|| |
Pandemic H1N1/09 virus is a novel strain of influenza A which is derived originally from a strain that lived in pig. The virus first evolved around September 2008 and circulated in the human population for several months before the first cases were identified. Following its emergence, H1N1 virus spread rapidly throughout the world. The virus spread in such a manner that on June 11, 2009, WHO declared a pandemic alert level of six.  The disease started in India in the month of May 2009. Soon the disease spread to other parts of the country. The first case in the state of Rajasthan was seen much later on July 23, 2009. The present study was based on all confirmed cases of H1N1in western Rajasthan from month of August 2009 to March 2010.
We observed more cases in males (54%) compared to females (46%). Puvanalingam et al. (2011) in their study involving 2government hospitals in Chennai observed similar findings.  This may be partly because males of more exposed to the environmental predisposition to the virus than females. The seasonal influenza A virus is believed to affect the individuals in extremes of age. However, H1N1 strain affects predominantly the younger population. Our observed the high proportion of cases (61.51%) in the age group of 16-45 yearsis similar to that reported in previous studies. ,, The likely reason may be the higher immunity of younger individuals. Higher immunity is associated with a robust immunological response and cytokine storm making the disease to be more clinically apparent. The suspected as well as confirmed cases rose during the winter months of December, January, and February. This is not unexpected as H1N1 is a viral disease that spreads via aerosols.
We recorded case fatality rate of 11.69% which is higher than that reported from other parts of the world (0.3-0.4%).  In contrast, Puvanalingam et al. (2010) observed case fatality rate of 1.8% and Samra et al. (2011) in their study in tertiary care hospital in Northern India reported case fatality rate of 5%. ,
The predominance males infection compared to females and the higher case fatality rate in in females compare to males are is similar to the report in some previous studies. ,,,
We recorded higher frequency of deaths among the young age group, 16-30 years (12.75%, 19.69% respectively. In contrast, Rana et al. (2012) in their study observed a case fatality of 26.8%.  Case fatality rate was significantly higher in rural (18.38%) than urban area (7.24%) in our study.
Case fatality H1N1 influenza was also high (24.03%) in pregnant women. This is similar to the findings of Puvanalingam et al. (2010). 
| Conclusion|| |
H1N1 was more frequent among young age groups and occur mainly during the winter months in the study population. Severe illness and higher case fatality was observed among the pregnant and postpartum women.
| References|| |
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[Table 1], [Table 2], [Table 3], [Table 4]