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SHORT COMMUNICATION
Year : 2012  |  Volume : 56  |  Issue : 3  |  Page : 242-244  

Epidemiology of pandemic H1N1 strains in a tertiary hospital of Maharashtra


1 Associate Professor, Department of Microbiology, Indira Gandhi Government Medical College, Nagpur, India
2 Research Scientist, Department of Microbiology, Indira Gandhi Government Medical College, Nagpur, India
3 Lecturer, Department of Microbiology, Indira Gandhi Government Medical College, Nagpur, India
4 Professor & Head, Department of Microbiology, Indira Gandhi Government Medical College, Nagpur, India

Date of Web Publication3-Dec-2012

Correspondence Address:
Sunanda Shrikhande
Associate Professor, Department of Microbiology, Indira Gandhi Government Medical College, Nagpur, Maharashtra
India
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DOI: 10.4103/0019-557X.104267

PMID: 23229220

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   Abstract 

Swine-flu is a viral fever caused by a new mutated strain Influenza A virus subtype H1N1, which infects humans. Pandemic H1N1 (pH1N1/2009) virus was detected in the first quarter of 2009 in the west coastal region of North America and spread very rapidly to the other countries during April-June, 2009. This study was conducted to assess the epidemiology of pandemic H1N1 strains using a cross-sectional study design in a tertiary hospital. The symptomatic patients attending the flu outpatient department (OPD)/emergency from August 2009 to April 2011 at Indira Gandhi Government Medical College, Nagpur were included using a standard case definition. A total of 67 (27.01%) samples from 247 patients were pandemic influenza A/H1N1 positive. None of the patients had a history of foreign travel, whereas 23.88% of the patients gave history of travel to an endemic area. Overall, 22.38% of the patients came in contact with proven cases of pandemic H1N1. pH1N1 transmission activity has increased since May 2010.

Keywords: Nagpur, Pandemic H1N1, Swine-flu


How to cite this article:
Shrikhande S, Bhoyar S K, Tenpe S H, Deogade N G. Epidemiology of pandemic H1N1 strains in a tertiary hospital of Maharashtra. Indian J Public Health 2012;56:242-4

How to cite this URL:
Shrikhande S, Bhoyar S K, Tenpe S H, Deogade N G. Epidemiology of pandemic H1N1 strains in a tertiary hospital of Maharashtra. Indian J Public Health [serial online] 2012 [cited 2014 Sep 22];56:242-4. Available from: http://www.ijph.in/text.asp?2012/56/3/242/104267

Pandemic H1N1 (pH1N1/2009) virus was detected in the first quarter of 2009 in the west coastal region of North America and spread very rapidly to other countries during April-June, 2009. [1],[2] The World Health Organization (WHO) formally declared the pandemic (Phase 6) on June 11, 2009. [2] As of August 1, 2010, more than 214 countries had reported laboratory confirmed cases of pH1N1/2009 virus, with over 18,449 deaths worldwide. [2] This virus is unique compared with the viruses causing previous pandemics with higher transmission ability; but a low virulence compared with previous pandemic viruses of this century. [3] The first positive case of P-09-H1N1 in India was reported on May 16, 2009 at Hyderabad airport who was a 23-year-old with history of traveling to the United States. [4] The virus soon spread to almost all major cities in India.

Swine-flu is a viral fever caused by a new mutated strain influenza A virus subtype H1N1, which infects humans. This novel virus is a combination derived from a reassortment of six gene segments from the triple reassortant swine-origin virus and two gene segments from the Eurasian influenza A (H1N1) swine virus lineage. [5]

Antigenic variation through antigenic-drift and antigenic-shift of hemagglutinin (HA) and neuraminidase (NA) proteins enables the virus to escape host immune responses. [6] Antigenic drifts in the HA subtype are associated with seasonal epidemics. Although the precise mechanism is unknown, shifts are widely assumed to be facilitated by the virus's segmented genome and the genetic diversity it achieves by infecting a varied reservoir of animals. [6] Antigenic shifts in HA subtypes are associated with pandemics.

This observational study was planned to assess the epidemiology of pandemic H1N1 strains in a tertiary care hospital in Maharashtra and was approved by the institutional ethics committee. In this hospital-based cross-sectional study, we enrolled symptomatic patients attending the flu OPD/emergency from August 2009 to April 2011 at Indira Gandhi Government Medical College, Nagpur. Samples were collected from patients of all age groups who met the criteria of case definition of influenza like illness (ILI), like with a history of international travel from the country of confirmed pandemic H1N1, or a close contact with a confirmed H1N1 infected person, or with shortness of breathing, or hospital admitted patients. ILI was defined as those with fever ≥38°C with at least one respiratory symptom such as cough, rhinorrhea, or sore throat. [7] Nasal/throat swabs were taken in a viral transport medium (VTM) after collecting relevant clinical and epidemiological information. All samples were sent to National Institute of Virology, Pune for Reverse Transcriptase - Polymerase Chain Reaction RT-PCR analysis.

A total of 248 patients with suspected pandemic influenza A/H1N1 were evaluated during the study period.

All the confirmed cases of pandemic influenza A/H1N1 were in the age range of 10-70 years with a mean age of 22 years. Most of the cases were found in the age range 21-30 years (38.80%), followed by 51-60 years (20.89%), and 41-50 years (14.92%) [Figure 1]. 67 (27.01%) were pandemic inflfluenza A/H1N1 positive with the fifirst case detected on August 14, 2009 [Figure 2].
Figure 1: Age wise distribution of H1N1 cases

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Figure 2: Seasonal distribution of H1N1 cases

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Among the positive cases 44 (65.67%) were male and 23 (34.32%) were female (ratio: 1.9:1). A total of 49.25% (n = 33) cases of pandemic H1N1 had associated medical ailments. Anemia and diabetes (8.95%) were the most common medical ailments associated with pandemic H1N1, followed by bronchial asthma (7.46%). None of the patients had a history of foreign travel, whereas 23.88% of the patients gave history of travel to endemic area. Overall, 22.38% of the patients came in contact with proven cases of pandemic H1N1.

Laboratory tests required for etiology-specific diagnosis are not widely available in India. Unlike temperate climate countries where seasonal influenza incidence reaches epidemic proportions during winter months, [4] in tropical countries like India, a year-round circulation of strains has been reported, although the infection peaks during rainy season (June-September). [8]

Although the classical season of influenza is in winter, the peak of the cases coincided with the rainy season at our study site. The two months of August and September, which reported the largest block on cases, also witnessed the progressions of the rainy season and a high amount of relative humidity in the air. No cases of H1N1 were reported in October, which also witnessed a sharp fall in the amount of rain received locally in the region.

A characteristic feature of the H1N1 pandemic is that it disproportionately affected children and young adults. [9] Similar results were observed in different parts of the world. [10] In most countries, the majority of pandemic influenza A (H1N1) cases have been occurring in young people, with the median age estimated to be 12-17 years in Canada, USA, Chile, Japan, and UK. Most of the pandemic influenza cases in young age people indicate toward partial immunity to the virus in the older population. [1] In this study, young adults aged between 21 and 30 years and comprised nearly a third of the cases. Although this is a working age-group with higher risk of exposure to groups during their working hours, the predilection of the disease in this age group merits closer examination. This observation could also be confounded by the exposure and level of immunity against other influenza viruses in circulation. The health care seeking behavior in India shows a trend of self-medication with an easy availability of prescription drugs across the counter. This could have resulted in selective appearance of some population groups in a tertiary hospital and is a major limitation of our study design.


   Acknowledgement Top


We would like to acknowledge all the staff working in ICMR Influenza Project at Indira Gandhi Government Medical College, Nagpur for their contribution during the study. We are grateful to National Institute of Virology, Pune for for RT-PCR analysis of specimens.

 
   References Top

1.Novel Swine-Origin Influenza A (H1N1) Virus Investigation Team, Dawood FS, Jain S, Finelli L, Shaw MW, Lindstrom S, et al. Emergence of a novel swine-origin influenza A (H1N1) virus in humans. N Engl J Med 2009;360:2605-15.  Back to cited text no. 1
[PUBMED]    
2.WHO. Pandemic (H1N1) 2009 - update 112 [Internet]: WHO; 2009. Available from: http://www.who.int/csr/don/2010_08_06/en/index.html. [Last cited 2012 Jun 4].  Back to cited text no. 2
    
3.Outbreak of swine-origin influenza A (H1N1) virus infection - Mexico, March-April 2009 [Internet]. Available from: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm58d0430a2.htm. [Last cited 2012 Jun 4].  Back to cited text no. 3
    
4.John TJ, Moorthy M. 2009 pandemic influenza in India. Indian Pediatr 2010;47:25-31.  Back to cited text no. 4
[PUBMED]    
5.Antigenic and genetic characteristics of swine-origin 2009 A (H1N1) influenza viruses circulating in humans [Internet]. Available from: http://www.sciencemag.org/content/325/5937/197.abstract. [Last cited 2012 Jun 4].  Back to cited text no. 5
    
6.Mandell G, Bennett J, Dolin R. Mandell, Douglas, and Bennett's principles and practice of infectious diseases. 6 th ed. Philadelphia: Elsevier Churchill Livingstone; 2005.  Back to cited text no. 6
    
7.CDC H1N1 Flu H1N1 Flu and You [Internet], Available from: http://www.cdc.gov/h1n1flu/qa.htm. [Last cited 2012 Jun 4].  Back to cited text no. 7
    
8.Agrawal AS, Sarkar M, Chakrabarti S, Rajendran K, Kaur H, Mishra AC, et al. Comparative evaluation of real-time PCR and conventional RT-PCR during a 2 year surveillance for influenza and respiratory syncytial virus among children with acute respiratory infections in Kolkata, India, reveals a distinct seasonality of infection. J Med Microbiol 2009;58:1616-22.  Back to cited text no. 8
[PUBMED]    
9.Kwan-Gett TS, Baer A, Duchin JS. Spring 2009 H1N1 influenza outbreak in King County, Washington. Disaster Med Public Health Prep 2009;3 Suppl 2:S109-16.  Back to cited text no. 9
[PUBMED]    
10.AlMazroa MA, Memish ZA, AlWadey AM. Pandemic influenza A (H1N1) in Saudi Arabia: Description of the first one hundred cases. Ann Saudi Med 2010;30:11-4.  Back to cited text no. 10
[PUBMED]  Medknow Journal  


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