There is a lot of current interest in swine flu which has rapidly spread through like a wild fire across several areas of the world. Swine influenza, also known as swine flu, hog flu and pig flu, refers to influenza caused by those strains of influenza virus called swine influenza virus (SIV) which usually infect pigs. Swine influenza is common in pigs in the mid-western United States, Mexico, Canada, South America, Europe including the United Kingdom, Sweden, Italy, Kenya, Mainland China, Taiwan, Japan and other parts of Eastern Asia.

Transmission of the real swine influenza virus from pigs to humans is not common and properly cooked pork poses no risk of infection. When transmitted, the virus does not always cause human influenza and often the only sign of infection is the presence of antibodies in the blood, detectable only by laboratory tests. When transmission results in influenza in a human, it is called zoonotic swine flu, implying that it has spread from swine to man. People who work with pigs, especially people with intense exposures, are at risk of catching real swine flu. However, only about fifty such transmissions have been recorded world over since the mid-20th century, when identification of influenza virus subtypes became possible. It is only rarely that these strains of swine flu can pass from human to human. In humans, the symptoms of swine flu are similar to those of influenza and of influenza-like illness in general, namely chills, fever, sore throat, muscle pains, severe headache, coughing, weakness and general discomfort.

The 2009 flu outbreak in humans, known loosely and generally as "swine flu", is due to a new strain of influenza A virus. It is caused by a virus that probably had its initial origin in swine but which has undergone some mutant changes to make it an entirely new strain of the original. It is the virus subtype Influenza A/H1N1 that contains genes that are most closely related to swine influenza. The real true origin of this new strain is unknown and it is perhaps incorrect to refer to it as plain and simpleflu". World Organization for Animal Health (OIE) reports that this strain has not been isolated in pigs. This particular type of altered virus can be transmitted from human to human and causes the usual symptoms of influenza.

The original H1N1 form of swine flu is one of the descendants of the strain that caused the 1918 flu pandemic. As well as persisting in pigs, the descendants of the 1918 virus have also circulated in humans through the 20th century, contributing to the normal seasonal epidemics of influenza. However, direct transmission from pigs to humans is rare, with only 12 cases in the U.S. since 2005. Nevertheless, the retention of influenza strains in pigs after these strains have disappeared from the human population might make pigs a reservoir where influenza viruses could persist and later emerge to re-infect humans once human immunity to these strains has waned. The new strain was initially described as an apparent mixture of at least four strains of influenza A virus subtype H1N1, including one strain endemic in humans, one endemic in birds, and two endemic in swine. Subsequent analysis suggested it was a re-assortment of just two strains, both found in swine. It is imperative to emphasise that the current 2009 A/H1N1 virus is not zoonotic swine flu as it is not transmitted from pigs to humans but has the propensity to spread from person to person.

The present spread of the A/H1N1 strain of the virus was first reported from Mexico and the USA, spreading from human to human. Like all other flu viruses, this virus too spreads primarily by droplets emanating from coughing or sneezing spreading to other humans through the air. It could also spread by people touching an article that has been contaminated by the virus and subsequently touching the nose or mouth. The symptoms of the disease include fever, cough, sore throat, body aches, headache, chills and fatigue. There are some reports of vomiting and diarrhoea in some cases. The main problem with the disease is a form of rather nasty pneumonia that could occur in some people. Many of the deaths are due to this problem. An affected person remains infective from about a day prior to the onset of the disease to about a week after and in children this may go up to about ten days. Although no particular predilection of the disease to affect children has been identified so far, the propensity for them to readily acquire respiratory infections makes them a significant at-risk population. People in the extremes of life are more susceptible to develop respiratory infections.

Specific diagnosis of the current A/H1N1 disease can be quite difficult as the illness closely resembles any other form of flu. Esoteric and sophisticated tests such as virus isolation by culture and polymerase chain reaction (PCR) could definitely prove that the disease is caused by the currently prevalent A/H1N1 strain. These tests are quite expensive and are not freely available in many countries including Sri Lanka. A diagnosis of confirmed swine flu requires laboratory testing of a respiratory sample such as a simple nose and throat swab. A rise in the specific A/H1N1 antibodies is useful for diagnosis but as it takes time for the antibodies to appear, it occurs rather late in the disease.

Once diagnosed, there are at least two anti-viral drugs that have been shown to be useful in the treatment. Antiviral drugs can make the illness milder and make the patient feel better faster. They may also prevent serious flu complications. The use of these drugs as a preventive measure in areas in which there are epidemics is still controversial and not a firmly established evidence based practice. At present there is no effective vaccine against the current A/H1N1 strain. Wearing of protective masks in areas where the disease is rampant and covering the nose and mouth with a tissue during coughing will be useful. The used tissue must be discarded at once and the common practice of using the tissue repeatedly and keeping it in clothing pockets or handbags is certainly not going to be an effective measure. Washing the hands with soap and water, especially after coughing too, is advocated but is perhaps not universally practicable. Avoiding crowds and not attending to work and schooling if one feels ill with an influenza like illness are other advocated measures. These measures are known as "social distancing". Swine flu cannot be spread by pork products since the virus is not transmitted through food and there is no reason to stay away from well cooked pork.

The 2009 outbreak of influenza A/H1N1 virus is an epidemic of a new strain of influenza virus that was clinically identified in April 2009 and is commonly referred to as swine flu. It is currently a Phase 5 outbreak, one stage below the top level of an official pandemic. Although the exact origin of the outbreak is unknown, it was first detected when officials in Mexico and the United States suspected a link between an outbreak of late-season flu cases in Mexico and cases of influenza in Texas and California. Within days, hundreds more suspected cases were discovered in Mexico with more cases also showing up in the U.S. and several other countries. By late April, the officials from the United Nations, those from The World Health Organization (WHO) based in Switzerland and the Centers for Disease Control and Prevention (CDC) in Atlanta, USA, were expressing serious concern about the flu outbreak, worried that it might become a worldwide flu pandemic. As a result, WHO raised its alert level to "Phase 5" out of 6 possible, which it defines as a "signal that a pandemic is imminent". Up to date, close to 2000 cases have been identified in 23 countries.

By the end of April 2009, many governments across the world had taken emergency measures to slow the transmission of a possible pandemic. At the same time however, many scientists were reaching a consensus that the "epidemic" which until May 6 has had fewer than 31 deaths confirmed worldwide, was so far relatively "extremely mild" and believed that it could be less fatal than previous pandemics. However, it must be remembered that as time goes on, one of two things can happen. The virulence of the virus may get blunted after repeated passage through humans or it may become devastatingly potent and dangerous by undergoing further mutant changes. Thus the further progress of the disease remains quite unpredictable and the state of play would remain to be seen.

As at present, the World Health Organisation has indicated that the epidemic has reached potentially serious proportions, at least in some countries. Quite fortunately the disease does not seem to have reached Sri Lanka as yet. There is however no reason for complacence as it could arrive in the country at any time and all efforts must concentrate on preventing the entrance of the disease through international air and sea travel. Towards that end stringent observational and control measures together with quarantine of suspected cases at our international airport is of paramount importance. It is probably not sufficient just to have a thermal scanner to detect passengers with fever. Authorities who just install such a scanner and think that it by itself would be a panacea for all ills in swine flu are indeed living in a fools’ paradise. All suspected cases must be thoroughly examined, carefully evaluated and quarantined whenever necessary. As we do not have the facilities for intensive laboratory testing, clinical vigilance would be the order of the day. No doubt, this is a huge task and will need a tremendous amount of medical manpower at the airport but it is the real need of the hour. There is no point whatsoever in stopping the consumption of pork or checking, pigs, piggeries and those who work with pigs as that would be an entirely lost cause and an absolute waste of scarce resources.

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