As if the economic slump wasn’t enough, the world is today reeling under a new terror, the Swine Flu.
Swine influenza, the first of its kind outbreak in 21 century, is well underway and also brings along innumerable problems – not just the illness but also a huge hype over the whole concept.
So what is Swine flu?
Swine influenza or Swine flu is a zoonotic disease, i.e. an infectious disease transmitted from animals to humans; the animal vector here being the pig. The endemic is also known as H1N1 flu, pig flu, Mexican Flu, etc.
The endemic is can be caused by three strains of swine influenza virus (SIV), namely Influenza A, B and C.
Of the three genres, Influenza A and C also infect pigs, with influenza A being common and C being rare. However, Influenza C viruses do not infect birds and the B variety has not yet been reported in pigs.
Within influenza A and influenza C, the strains found in pigs and humans are largely distinct. Although, due to mutation transfers of genes among strains crossing swine, avian, and human species are found at large.
All flu viruses — human, bird, pig — have an “H” and an “N” in the name, each followed by a number. The letters refer to two proteins (hemagglutinin and neuraminidase) on the surface of the virus and the numbers refer to slight variations in the form of each protein.
The 2009 outbreak of swine flu is known to be caused by influenza A subtypes, H1N1, H1N2, H3N1, H3N2, and H2N3. The H1N1 viral strain implicated in the 2009 flu pandemic among humans is called "swine flu" because initial testing showed many of the genes in the virus were similar to influenza viruses normally occurring in North American swine.
How and when the world caught virus?
The first instance of the epidemic in human beings was found during the 1918 flu pandemic, when pigs and humans became ill simultaneously.
The 1918 outbreak was not the last of its kind. The first identification of an influenza virus in pigs occurred in 1930. In 1997-1998, H3N2 strains emerged. Going forward, there were several similar outbreaks in the years that came by, such as 1976 US outbreak, 1988 zoonosis, 1998 US outbreak in swine, 2007 Philippine outbreak in swine, and the latest 2009 outbreak in humans.
Direct transmission of a swine flu virus from pigs to humans, (called zoonotic swine flu), is rare. However, the 2009 H1N1 virus is not zoonotic swine flu, as it is not transmitted from pigs to humans, but from person to person. Researches have found that the outbreak is due to a new strain of H1N1 not previously reported in pigs.
The new strain was thought to be a mutation of four known strains of the influenza A virus A virus subtype H1N1, including one strain endemic in humans, one endemic in birds, and two endemic in swine. However, subsequent analysis suggested that it was a mutation of just two strains, both found in swine.
Mode of transmission
Among Pigs, the virus spreads through direct contact, common during animal transport, either when pigs touch noses, or through dried mucus. Intensive farming may also increase the risk of transmission, as the pigs are raised in close proximity.
Airborne transmission through aerosols produced by pigs coughing or sneezing are also important means of infection The virus usually spreads quickly through a herd, infecting all the pigs within a few days.
On the other hand, in humans, people who work in poultry, especially with intense exposures, are at high risk of this infection. Veterinarians and meat processing workers fall under the lesser risk category.
Symptoms: Are you sick?
The most common cause of death is respiratory failure, other causes of death are pneumonia (leading to sepsis), high fever (leading to neurological problems), dehydration (from excessive vomiting and diarrhea) and electrolyte imbalance. Fatalities are more likely in young children and the elderly.
Among infected pigs, fever, lethargy, sneezing, coughing, breathing troubles and less appetite are the common symptoms. In extreme cases, it can also lead to abortion. Infected pigs can lose up to 12 pounds of body weight during a three to four week period.
As per Center for Disease Control and Prevention (CDC), in humans the symptoms of the 2009 "swine flu" H1N1 virus are similar to those of influenza and of influenza-like illness in general. Symptoms include fever, cough, sore throat, body aches, headache, chills and fatigue. The 2009 outbreak has shown an increased percentage of patients reporting diarrohea and vomiting.
However, since 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 history and also requires laboratory testing of a respiratory sample (a simple nose and throat swab).
Prevention is better than cure
Swine flu preventive measure consist of three components:
Prevention in swine
This includes facility management, herd management, and vaccination.
It has been found that swine flu related illness and deaths are more or less caused by secondary infection. Thus mere vaccination may be insufficient, especially of late, when mutated influenza virus variants, H3N2 SIV, do not respond to traditional vaccines.
The United States Department of Agriculture researchers say that while pig vaccination keeps pigs from getting sick, it does not block infection or shedding of the virus.
Facility management includes using disinfectants and ambient temperature to control virus in the environment. The virus is unlikely to survive outside living cells for more than two weeks, except in cold (above freezing) conditions, and it is readily inactivated by disinfectants.
Herd management includes avoiding adding infected pigs into herds that have not been exposed to the virus. The virus survives in healthy carrier pigs for up to 3 months and can be recovered from them between outbreaks. Carrier pigs are usually responsible for the introduction of SIV into previously uninfected herds and countries, so new animals should be quarantined. After an outbreak, as immunity in exposed pigs wanes, new outbreaks of the same strain can occur.
Preventing pig to human transmission
Swine farmers and veterinarians are encouraged to use a face mask when dealing with infected animals. The use of vaccines on swine to prevent their infection is a major method of limiting swine to human transmission. Risk factors that may contribute to swine-to-human transmission also include smoking.
Preventing human to human transmission
Influenza spreads between humans through coughing or sneezing and via direct contact. However, Swine flu cannot spread by pork products, since virus is not transmitted through food.
Incubation period for this virus is said to be 24 to 48 hours (2 to 7 days). The swine flu in humans is most contagious during the first five days of the illness although some people, most commonly children, can remain contagious for up to ten days.
People are recommeneded to keep their surroundings clean, wash hands with soap and water or with alcohol-based hand sanitizers, especially after being out in public. Chances of transmission is also reduced by disinfecting household surfaces, which can be done effectively with a diluted chlorine bleach solution.
Social distancing is another mode of prevention. Public health and other responsible authorities have action plans which may request or require social distancing actions depending on the severity of the outbreak.
Cure at hand
Swine influenza is rarely fatal to pigs. However, efforts are focused on preventing the spread of this virus with the help of vaccination and animal management techniques. Antibiotics are also used, which although have no effect against the influenza virus, do help in preventing bacterial pneumonia and other secondary infections in influenza-weakened herds.
Similarly, infected people also make full recovery without any medical attention or anti-viral drugs. However, although the 2009 variant of swine influenza found to be resistant to amantadine and rimantadine, the US Centers for Disease Control and Prevention recommends the use of Tamiflu (oseltamivir) or Relenza (zanamivir).
Antiviral drugs work best within two days of symptoms. Beside antivirals, supportive care at home or in hospital, focuses on controlling fevers, relieving pain and maintaining fluid balance, as well as identifying and treating any secondary infections or other medical problems.
Although the current trivalent influenza vaccine is unlikely to provide protection against the new 2009 H1N1 strain, vaccines against the new strain are being developed and could be ready as early as June 2009.
