By Dr. Muzafar Jan
A swine origin H1N1 virus, commonly known as swine flu, virus has claimed millions of lives across globe and epidemiologically is classified as a pandemic, that is, it is a global epidemic. In India, there has been also an outbreak of H1N1 pandemic in 2009 which took thousands of lives and still continues. Furthermore, every year, there is a rise in the incidence of H1N1 infections particularly during winters as the virus thrives in cold temperatures. Jammu and Kashmir, being a cold region, is prone to H1N1 outbreak which, as per latest reports, has already claimed fives precious lives (five more are being treated in Kashmir while similar number of cases were reported from Jammu area this year). It is important to understand the biological nature of this virus mode of transmission prognosis and its preventive measures.
H1N1 belongs to orthomyxovirus family containing exclusively RNA viruses and influenza viruses or flu viruses responsible for all flu pandemics come under this category of viruses. The virus on its outer surface in science terminology known as envelope has a coating of two large proteins hemagglutinin (HA) and neuraminidase (NA). It is from these two proteins HN naming system of viruses in this group has been adapted, for example, H1N1. The virus recognizes and binds to host cells using hemagglutinin (H) protein which has a very high tendency to bind sugars or carbohydrates on human and other host cells. The sugars are very prominently expressed on human and other host cells- blood group in humans is determined by the types of sugars expressed on bloodcells.The newly formed viruseswithin the infected cells get attached to the cells by sugars and neuraminidase (N) cleaves or breaks the sugar residues to release the newly formed virus particles in preparation to attack new uninfected cells.
The H and N come in different flavours with slight differences (H1-118 and N1-11), can have any permutations and combinations and is used to determine the virus subtype like the H1N1 flu virus; H5N1 avian (bird) flu virus; H2N2 asian flu virus.This hemagglutinin protein is also responsible for determining both which species a virus strain can infect and where in the human tract, it will bind. Those strains which are easily transmitted between people have receptors to bind in the upper respiratory tract, such as mouth, nose and throat while more lethal strains have receptors deeper in the respiratory tract like lungs.
Transmission and Preventive measures
The H1N1 virus is a miracle of evolution which has intermixed genes from three different viruses to establish itself as a dominant flu strain in most parts of the world. The H1N1 strain comprises of genes from the common human flu virus, an avian flu virus and a virus from pigs (swine). Scientists say that this triple H1N1 virus occurred 10-20 years ago and remained in pigs for years where it mixed with other swine viruses. The triple virus broke the species barrier to infect humans (called zoonosis) recently and was discovered first time in 2009.Usually, it becomes difficult to distinguish between common cold and flu in the early stages of infection. The flu has a mixture of symptoms of common cold and pneumonia including fatigue, headache, fever; sore throat, watery eyes, body aches, shortness of breath, weight loss, chills, sneezing, runny nose, coughing, dizziness, and abdominal pain, lack of appetite, and occasionally diarrhoea and vomiting.
Although, there is broad range of symptoms, however, these symptoms are not specific to swine flu ; a differential diagnosis of probable swine flu requires not only symptoms, but also a high likelihood of swine flu due to the person’s recent and past medical history. The common symptoms of flu accrue due to huge amounts of proinflammatory cytokines and chemokines, substances released by the immune system in response to infection. In contrast to rhinovirus, the causative agent of common cold, flu virus also causes tissue damage so symptoms are not entirely due to inflammatory response. This speedy function of immune system might produce a life threatening condition known as cytokine storm. A diagnosis of confirmed swine flu requires laboratory testing of a respiratory sample (a simple nose and throat swab).The most common cause of death with swine flu is failure of the respiratory system. Other symptoms of the disease may also progress to life threatening conditions which include dehydration from excessive vomiting and diarrhoea, electrolyte imbalance, kidney failure and high fever (leading to neurological problems. Fatalities are more likely in young children and the elderly.
In a single sneeze or cough, more than half a million virus particles are sprayed out. Flu is disseminated and spread in three different ways: direct transmission by sneezing or coughing when people stay in close aggregate groups, the airborne route when viral contaminated aerosols are being inhaled and by direct contact with infected person or contaminated surfaces through hand-to-eye, hand-to-nose, or hand-to-mouth transmission. The flu virus can persist outside of the body and can be transmitted by contaminated surfaces at home or at work. The length of time the virus will persist on a surface varies, with the virus surviving for one to two days on hard, non-porous surfaces such as plastic or metal, for about fifteen minutes from dry paper tissues, and only five minutes on skin. The highest rate of shedding of virus from infected individuals increases from one half to one day after infection and peaks on day 2 and persist for average total duration of 5 days and can persist as long as 9 days.
Children are much more prone to infection than adults and shed virus from just before they develop symptoms until two weeks after infection. In immunocompromised people, viral shedding can continue for longer than two weeks. There can be many effective ways to reduce the transmission of flu which include good personal hygiene habits such as: not to touch parts of body prone to infection including eyes, nose and mouth; making habit of routinely washing hands with soap and other available sanitizers; covering nose and mouth near cough and sneezes; avoiding contact with sick people. Although face masks might help prevent transmission when caring for the sick, there is mixed evidence on beneficial effects in the community.Smoking raises the risk of contracting influenza, as well as producing more severe disease symptoms.Since influenza spreads through both aerosols and contact with contaminated surfaces, surface sanitizing may help prevent some infections. Alcohol is an effective sanitizer against influenza viruses, while quaternary ammonium compounds can be used with alcohol so that the sanitizing effect lasts for longer. In hospitals, quaternary ammonium compounds and bleach are used to sanitize rooms or equipment that have been occupied by patients with influenza symptoms.At home, this can be done effectively with a diluted chlorine bleach. Social distancing strategies used during past pandemics, such as closing schools, and other public gathering places, slowed the spread of the virus but did not have a large effect on the overall death rate.
Kashmir is at Risk
During winters, the situation can get alarming in Kashmir because the virus thrives well in the winter. It is not known why the virus displays a seasonal pattern. However, latest research points out that cold temperatures and low humidity- the conditions in temperate zones in winter- are much more favourable for the virus transmission. The effects are on both virus and the humans ; during winters the temperature and humidity affect the virus and the environment affects the respiratory tracts of humans and other mammals. The flu virus seems more stable in cold dried conditions as the episodes of outbreak are more common during winters.
It has been long known that one of the favourable transmission modes of the virus is by coughing and sneezing. Particularly under low temperature and humidity , there is a specific effect on the droplets of fluid being coughed or sneezed away being much smaller in size. These droplets stay suspended longer in air due to their small size and get carried much farther. The propensity to stay longer in air and minuscule size, they are breathed in easily and in combination with dry cold conditions penetrate deeper into the respiratory passages and lungs. At higher humidity or high temperature, the droplets become much bigger and sink to the floor. Another factor that plays an important in the dissemination of the flu virus as can be commonly seen that that during colder drier conditions , the mucous is much more viscous. The entire respiratory tract is covered with tiny hairs called Celia that continually beat in waves to clear these tracts. During winters viscous mucus clogs these tiny hairs, arresting their motion due to which the thick mucus remains trapped which provides a rich nutritious platform for different infectious entities trapped in the mucus including viruses.
Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA.
The U.S. Food and Drug Administration (FDA), MD, USA.
National Institute of health (USA), MD, USA.
World Health organization (WHO), Geneva, Switzerland.
—The author is a Postdoctoral Fellow at the Viral Immuno-pathogeneis Lab, Icahn’s school of Medicine at Mount Sinai Manhattan, New York, USA. He can be reached at : [email protected] or [email protected]