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Year : 2011  |  Volume : 54  |  Issue : 2  |  Page : 323-325
Profile of H1N1 infection in a tertiary care center

Department of Microbiology, ESIC-PGIMSR, Rajajinagar, Bangalore-10, Karnataka, India

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Date of Web Publication27-May-2011


Background: A novel swine origin influenza virus (H1N1) is spreading worldwide and threatens to become pandemic.H1N1 critical illness mostly affects young patients and is often fatal. Aim: The aim of the present study is to evaluate the clinical characteristic of H1N1 infection in a tertiary care hospital. Materials and Methods: A total of 92 nasal and pharyngeal swabs from suspected cases of swine flu were processed by real time reverse transcriptase polymerase chain reaction (rRT-PCR). Result: Twenty(21.73%) were positive of which two were treating physicians and five (25%) patients expired. Conclusions: The age group of positive cases of H1N1 was between 21 and 30 years and age group of patients who died ranged from 40 to 45 year. This overview indicates that although the majority of hospitalized persons infected with novel influenza A (H1N1) recovered without complications, certain patients had severe and prolonged disease. It was also noted that 2009 influenza A (H1N1) infection - related clinical illness predominantly affects young patients. All hospitalized patients with novel influenza A (H1N1) infection should be monitored carefully and treated with antiviral therapy. Mandatory vaccination of health-care workers is especially important in emerging pandemic.

Keywords: H1N1, influenza A, respiratory failure, swine flu, upper respiratory tract infection

How to cite this article:
Jagannatha Rao S, Rao MJ, Swamy N, Umapathy B L. Profile of H1N1 infection in a tertiary care center. Indian J Pathol Microbiol 2011;54:323-5

How to cite this URL:
Jagannatha Rao S, Rao MJ, Swamy N, Umapathy B L. Profile of H1N1 infection in a tertiary care center. Indian J Pathol Microbiol [serial online] 2011 [cited 2021 Nov 28];54:323-5. Available from: https://www.ijpmonline.org/text.asp?2011/54/2/323/81618

   Introduction Top

A novel influenza A (H1N1) virus emerged in Mexico in early 2009 and has to date caused 9830 human infections. The virus is transmitting from human-to-human at least as efficiently as seasonal influenza viruses. [1]

After early outbreaks in North America in April 2009, the new influenza virus spread rapidly around the world. By the time World Health Organization (WHO) declared a pandemic in June 2009, a total of 74 countries and territories had reported laboratory-confirmed infections. To date, most countries in the world have confirmed infections from the new virus. [2]

The new virus has also led to patterns of death and illness not normally seen in influenza infections. Most of the deaths caused by the pandemic influenza have occurred among younger people, including those who were otherwise healthy. Pregnant women, younger children and people of any age with certain chronic lung or other medical conditions appear to be at higher risk of more complicated or severe illness. Many of the severe cases have been due to viral pneumonia, which is harder to treat than bacterial pneumonias usually associated with seasonal influenza. Many of these patients have required intensive care. [2]

Influenza A (H1N1) virus is a subtype of influenza A virus and was the most common cause of human influenza (flu) in 2009. Some strains of H1N1 are endemic in humans and cause a small fraction of all influenza-like illness and a small fraction of all seasonal influenza. H1N1 strains caused a few percent of all human flu infections in 2004-2005. [3]

   Materials and Methods Top

A total of 92 patients who presented to medical Out Patient Department (OPD) during August 2009 to April 2010 with suspected signs and symptoms of Swine Flu and who were categorized as belonging to Category C [4] were admitted to Swine Flu ward. The age group ranged from 14 to 70 years. A thorough physical examination was done. One nasal swab and one throat swab was collected under all aseptic and universal precautions and kept in Viral Transport Medium and sent to the testing center. Real-time Reverse Transcriptase Polymerase Chain Reaction (rRT-PCR) was done as per the CDC Protocol [5] for the detection of H1N1 and the reports were received at our hospital within 48 hours.

All the patients were investigated for Complete Blood Count (CBC), Fasting Blood Sugar (FBS)/Post Prandial Blood Sugar (PPBS), blood urea/serum creatinine, serum electrolytes, sputum for Grams stain, acid fast bacilli and bacterial culture and sensitivity, chest X-Ray, two-dimensional echocardiogram (2D-ECHO) and arterial blood gas analysis (ABG).

   Results Top

[Table 1] and [Figure 1] show the total number and age-wise distribution of suspected cases of H1N1, respectively.
Figure 1: Shows the age-wise distribution of 92 cases which were admitted to Swine Flu ward

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Table 1: Shows the sex-wise distribution of 92 cases which were admitted to Swine Flu ward

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A total of 20 cases of nasal swab and throat swab were positive for 4 markers used in real-time RT-PCR. They were Influenza A, Swine A, Swine H1 and ribonuclease P (RNAse P). The maximum number of positive cases were in the age group of 21-30 years (60%) followed by 31-40 years (30%) as shown in [Table 2] and [Figure 2].
Figure 2: Shows the age-wise distribution of confirmed cases as H1N1

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Table 2: Shows the sex-wise distribution of confirmed cases as H1N1

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[Table 3] shows the predominant symptoms in confirmed cases of H1N1 infection. The predominant complaints were productive cough, fever with chills and rigors, and breathlessness, although vomiting and diarrhea have been reported more commonly with H1N1 infection. [6] Only two of our patients had these symptoms.
Table 3: Symptoms of confirmed cases of novel H1N1 patients

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The systemic examination of H1N1 positive cases showed bilateral crepitations in 12 (66.6%), tachycardia in 8 (40%) and hypotension in 5 (25%). On radiological examination 6 (30%) had acute respiratory distress syndrome (ARDS) and 6 (30%) had bronchopneumonia.

Five (25%) H1N1 confirmed cases died, of these four were females and one male.

   Discussion Top

H1N1 infection is severe in younger and healthier people as noted. To date, most severe H1N1 infections and deaths have occurred in adults under the age of 50 years.H1N1 deaths in the elderly is comparatively rare. Severe respiratory failure, the most reported cause of death due to H1N1 pandemic infection is also in the young and otherwise healthy people. [6],[7],[8] In these patients the virus directly infects the lung causing severe respiratory failure.

Although serological studies suggest that 2009 influenza A (H1N1) is a novel influenza strain with little protection afforded by seasonal influenza vaccination, adults older than 60 years appear to have some preexisting immunity to this novel virus. [9]

Why the H1N1 strain becomes more aggressive with the young is not fully understood. It is suggested that H1N1 component, a sub-type of the virus protein hemagglutinin, in both swine flu and human flu has a common ancestor H1 circulated in humans, evolving continuously during the 1918 and 1957 influenza pandemics. H1 then became inactive, replaced by other subtypes of hemagglutinin such as H3. H1 in humans reappeared in 1977 and has been a dominant subtype of human flu ever since. Even though H1 has evolved significantly from 1977 to the present in humans, the H1N1 has evolved very little in pigs. Swine flu H1 has been very similar to the original 1918 and 1930 versions of H1. So it is assumed that most people born before 1957 who were exposed to human H1 influenza their immune systems produce antibodies to old H1. Since old H1 has not been seen in humans in many years, younger people do not have antibodies to make them immune to the old H1 which is very close to 2009 H1 swine flu. [8],[10]

Critically ill patients with diabetes and hyperglycemia also are known to be at increased risk of complications and death; similarly, alcohol abuse, which is known to be a risk factor for acute respiratory distress syndrome. These relationships also have been reported with seasonal influenza. [8]

It is well documented that underlying diseases could be contributory factors for the higher mortality. [11] In the present study, five (25%) H1N1 confirmed cases died, of these four were females and one male. Among these one patient had tuberculosis, one had chronic obstructive pulmonary disease with congestive cardiac failure, type 2 diabetes mellitus, ischemic heart disease and hypertension and one was a chronic alcoholic. There were no contributory factors for death in 2 other cases. There was a rapid downhill course of the infection ranging from 3 to 5 days from the date of admission to date of expiry. The cause of death was attributed to respiratory failure/sepsis. It was not known whether these two patients were on antibiotics, as antibiotics could have a negative impact on the immune status.

The relative absence of serious co-morbidities emphasizes that young, relatively healthy adults were the primary population affected by influenza A (H1N1) infection during this outbreak. Though certain patients had severe and prolonged disease, the preliminary overview indicates that majority of hospitalized persons infected with novel influenza A (H1N1) recovered without complications. Careful monitoring and treatment with antiviral therapy of hospitalized patients with novel influenza A (H1N1) infection should be emphasized, including patients who seek care >48 hours after illness onset.

Two symptomatic doctors exposed to H1N1 patients were tested positive for H1N1. This highlights the need for precautions to be taken while examining the patients and need for immunization. Mandatory vaccination of healthcare workers is especially important in an emerging pandemic, which, although is still relatively mild, has shown the capability of causing severe illness and death, and can also get worse as it continues to spread. The purpose of vaccinating healthcare workers is to decrease the amount of circulating virus and lower the risk that it will spread to those in higher risk groups.

   References Top

1.Chan KH, Lai ST, Poon LL, Guan Y, Yuen KY, Peiris JS. Analytical sensitivity of rapid influenza antigen detection tests for swine-origin influenza virus (H1N1). J Clin Virol 2009;45:205-7.  Back to cited text no. 1
2.World Health Organisation. Global Alert and Response. Geneva; WHO; Feb 24 2010.  Back to cited text no. 2
3.Centres for Disease Control (CDC). Influenza Summary, 2004-2005. Influenza (Flu): WeeklyReport.Season". http://www.cdc.gov/flu/weekly/weeklyarchives 2005-2006/05-06summary.htm.  Back to cited text no. 3
4.Revised Guidelines for Management of Cases of H1N1 Influenza (Swine Flu). As published by Union Health Ministry, Govt. of India; 2010.  Back to cited text no. 4
5.CDC protocol of real time RTPCR for Influenza A (H1N1) April 28, 2009 revision 2. Published from The WHO collaborating centre for Influenza at CDC Atlanta, United States of America: 2009.  Back to cited text no. 5
6.H1N1 early outbreak and disease characteristics, Centre for Disease Control and Prevention. Hist Arch 2009 pg.1-6.( http://www.cdc.gov/h1n1none flu/surviellanceqa.htm )   Back to cited text no. 6
7.Swine H1N1 Explosion in the United States, Recombinomics Commentary 15:18, June 9, 2009.  Back to cited text no. 7
8.Laurie Barclay, MD, Medscape Medical News. H1N1 Critical Illness Mostly Affects Young Patients and Is Often Fatal.  Back to cited text no. 8
9.Centers for Disease Control and Prevention (CDC). Serum cross-reactive antibody response to a novel influenza A (H1N1) virus after vaccination with seasonal influenza vaccine. MMWR Morb Mortal Wkly Rep 2009;58:521-4.  Back to cited text no. 9
10.Seth J. Sullivan, Robert M. Jacobson, Walter R. Dowdle, Gregory A. Poland. 2009 H1N1 Influenza. Mayo Clinic Proceedings 2010;85:64-76.  Back to cited text no. 10
11.Paul J, Srivastav A. Swine flu: Current perspective in 2010 in the proceedings of scientific sessions of 65 th Annual conference of physicians of India - Medicine update 2010;20:65.  Back to cited text no. 11

Correspondence Address:
Srinivasa Raghu Jagannatha Rao
Department of General Medicine, ESIC-PGIMSR, Rajajinagar, Bangalore-560010
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0377-4929.81618

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  [Figure 1], [Figure 2]

  [Table 1], [Table 2], [Table 3]

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