In recent years several disease outbreaks like Ebola virus, Avian Influenza A virus, Middle East Respiratory Syndrome coronavirus (MERS-CoV) have paralyzed the lives of millions across the globe. The current outburst of Influenza virus A, Swine Flu has claimed and is still claiming thousands of lives along with a high morbidity rate. In the year 2009, the virus was first detected in Mexico and started intruding to other parts of the United States and gradually to the entire world. HIN1 upsurge claimed nearly 50,000 lives worldwide. Looking at the gravity of the situation the World Health Organization (WHO) has declared it a ‘pandemic. ’
In India, the situation is no better. This year the flu virus has claimed as many as 1000 lives so far. Till now a total of 22,186 cases have been registered, and the figure increases with each passing day! The situation is getting worse with each passing year as well. In current year approximately 1094 deaths and 22,196 cases have been observed as compared to 265 deaths and 1786 swine flu cases in the year 2016. The highest number of people succumbing to the deadly viral infection have been reported in Maharashtra (467), followed by Gujarat (269), Kerala (73) and Rajasthan (69). The disease is slowly gripping its roots to other parts of the nation as well.
What is Swine flu?
Swine Flu is a contagious respiratory infection caused by one of the several strains of the Influenza Virus. The virus belongs to the family Orthomyxoviridae.
These RNA viruses have a genome that is approximately 13.5 kbps in size and is segmented into 8 coding regions that code for 11 different proteins:
- Envelope proteins: Hemagglutinin (HA) and Neuraminidase (NA).
- RNA Basic Polymerase: PA, PB-1, PB1-F2, and PB-2.
- Matrix Proteins: M1 and M2.
- Non-structural Proteins: NS-1 and NS-2.
HA and NA are the major surface glycoproteins that are responsible for viral attachment, replication, and pathogenesis and thus, are the main targets for antiviral drugs. These pathogens fast mutate into new strains by re-assorting the HA and NA genes and this is the main roadblock in the treatment of flu virus
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The RNA viruses are classified into three genera based on their antigenic differences1 in their nucleoprotein and matrix protein- Influenza virus A, Influenza virus B and Influenza virus C.
Influenza virus A cause severe flu outbreaks in domestic poultry and are the most virulent human pathogens that are mainly responsible for giving rise to human influenza pandemics. They are further subdivided into different serotypes2 based on the antibody response to these viruses- H1N1 (Swine flu pandemic 2009), H1N2, H2N2, H3N2, H5N1, H7N7, H7N2, H7N3, H10N7, and H7N9.
Influenza virus B mainly infects humans but is less pathogenic than Type A. They do not result in pandemics.
Influenza virus C targets humans, dogs, and pigs but they are less common than the other types and cause mild disease.
How the virus does attacks and invades the host body?
When the virus enters the host body it attaches to the sialyl moiety3 of the target cell surface. This binding is highly specific in nature. The whole invasion process can be summarised below:
Viral particles attach to the sialyl moiety of the host cell
Viral particles then enter the host cell via the process of endocytosis4
Transcription of the viral RNA genome by RNA polymerase
m-RNA is processed into ss-RNA using host cell machinery
Assembly, maturation, production, and release of new viral progenies.
As the viral progenies are released they target other cells and this marks the onset of infection. The incubation period5 of the flu is 2-4 days.
Once the incubation period is over the symptoms begin to appear. The common signs of the diseased state are chills, fever, running nose, sore throat, body aches, nausea, vomiting, diarrhea, and fatigue.
Pigs are the main reservoir of the virus and act as an intermediate host for interspecies transmission and genetic variation. The virus strains that infect humans are different from the strains that attack the swine population. It spreads through saliva and mucus particles that are released when an infected person or pig coughs, sneezes or touching the germ-covered surface or eyes. SWINE FLU IS NOT CAUSED BY EATING PORK MEAT.
What are the possible treatments available?
The treatment regimen includes drugs that precisely inhibit progeny virion production. These drugs are Zanamivir (Relenza), Peramivir (Rapivab), Favipiravir Oseltamivir (Tamiflu). The first three drugs are administered intravenously while Tamiflu is given orally. Many times combination drug therapy is also administered for effective treatments. E.g. Favipiravir is given in addition to Oseltamivir and Zanamivir. This drug amalgam efficiently inhibits the RNA polymerase of viral particles, thus, checks viral replication.
Apart from drugs Flu vaccination is the most preferred choice for reducing the risk of contracting the disease. Flu vaccines are composed of either live attenuated6 or killed viruses. When given to the body it triggers the immune system to produce antibodies against the virus and thus, protects the host.
The traditional flu vaccines that are made are protective against two influenza virus A strains namely H1N1&H3N2 and an Influenza virus B. This is trivalent vaccine5 (Vaccine that has three different antigenic sites). The other is quadrivalent that protects against the above three vaccines and an additional Influenza virus B strain. The Flu vaccine can be administered using either a needle or a nasal spray. The flu vaccine given using a needle (Flu Shot) are made in two ways: either using viruses that are inactivated or recombinant flu vaccine. The nasal spray flu vaccine contains live attenuated viruses. Both Flu Shot and Nasal spray flu vaccine are associated with some mild and short-lasting side effects-running nose, headaches, muscle aches, soreness, swelling at the place where vaccine is given, mild fever, to name a few. But in case if the flu vaccine causes some severe problems post vaccination then it is strongly recommended to consult the doctor.
Apart from the above vaccinations and treatments, it is of utmost importance to maintain personal hygiene and always use a hand sanitizer after coughing, sneezing or touching any of the diseased animal or person.
- Antigenic Variations is the mechanism with the help of which the pathogen alters its surface proteins to evade host immune system.
- Serotype is a distinct variation among different bacterial, viral species or immune cells of different individuals based on their difference in cell surface antigens.
- Sialyl moieties are sialic acid entities present at the terminus of the glycosylated oligosaccharide of the host cell surface.
- The process of taking in any matter by the living cell through membrane invagination.
- A period between exposure to the infection and appearance of the first symptom.
- Vaccines that are created by greatly reducing the virulence of the pathogen, keeping it alive.