Prevention is better Opinion & Comment / Technical Articles Posted by agrilive on Mar 07, 2004 - 02:10 PM Dr Soondus Aslam The disease, which is a source of widespread, panic these days and origin of multiple apprehensions is none other than Bird Flu. Being a clinician, I am always bombarded with question from all circles regarding the nature of this disease, the mode of its spread and, of course, how big a disaster it can be? So here are few answers. Flu is a viral disease caused by a family of viruses known as Orthomyxovirus. There are three members of this group: Influenza virus A, B & C. Type A influenza virus infects both birds as well as animals. "Avian Influenza viruses" infect wild birds as well as domestic birds (primarily found in wild birds only). "Mammalian Influenza virus", on the other hand, infects human beings as well as their close neighbours like pigs and horses. (Some strains are also found to infect seals and whales.) It is emphasised that Avian Influenza viruses do not usually directly infect humans or circulate among humans. Avian Influenza virus usually does not make wild birds sick but can make domestic birds very sick and kill them. This virus does not usually infect humans; however, several instances of human infections and outbreaks have been reported since 1997.When such infections occur, public health authorities monitor the situation closely because of concerns about the potential for more widespread infection in the human population. Influenza virus is segmented in nature. So it has ability to change its formulation. Once inside the host cell, eight segmented RNA genome of Influenza A virus undergoes high frequency recombination termed as reassortment leading to change in antigenic properties of virus. This change in antigenicity of virus is labelled as antigenic shift. Epidemics and Pandemics occur when antigenicity of the virus has changed sufficiently that pre-existing immunity of many people is no longer effective. Human Influenza virus has the property of contiguity. It very rapidly spreads from one person to another by micro-droplets emitted from nose and mouth of infected person while speaking, coughing or sneezing. While Avian Influenza virus has the property of causing deadly infection in human beings. If an Avian and Human Influenza A virus infect the same cell (e.g.: in a farmer's respiratory tract), reassortment could occur between them and a new variant of Human A virus could appear, which will be both, contagious as well as deadly and so it will cause the most devastating, quickly spreading pandemic which can erase the human race from the face of this earth. Spread of Influenza virus takes place via micro-droplets from one person to another. Similarly Avian Influenza virus can also spread from birds to human beings only by micro-droplets and essentially not by eggs and meat. To explain it further, if a bird (say chicken) was infected with Avian Influenza A virus in its lifetime, its meat or eggs will not transmit the virus to human beings. But a live infected bird can transmit virus to the person in close contact, that is, a bird fancier or a farmer. This forms the basis of extermination of whole farms or flocks of birds whenever flu is identified in domestic or farming birds. The incubation period of Influenza A virus is 1-4 days. Person infected can transmit virus one day before to seven days after the appearance of symptoms. This duration is known as period of infectivity. Symptoms, if not complicated by super-added bacterial infection or pneumonia, can spontaneously resolve within 4-7 days. Symptoms are fever, headache, malaise, myalgia, prostration, nausea, vomiting, conjunctivitis, eye pain(photophobia) and also depression. Complications can be as deadly as pneumonia caused by Pneumococcus, H.Influenzae or Staph aureus. Other complications can be Bronchitis, Sinusitis, Otitis needia, Encephalitis, Pericarditis, or Coma with deranged liver function tests. Diagnosis of influenza is based on clinical features and investigations. Laboratory test earliest to become positive is PCR (polymerase chain reaction), becomes positive within 36 hours. Other investigations, more of epidemiological interest, are: assay of antibody titre against Influenza virus by Haemagglutination inhibition test or by Complete fixation test and cell culture from throat washing and fluorescent antibody staining of infected cells for identification of virus in them. Even if a definitive diagnosis is established, there are not many treatment options available. Two Antiviral drugs, that is, Amantadine and Rimantadine are approved for both treatment as well as prevention of Influenza A. Main indication of these drugs is in prevention of Influenza in a confined, elderly unimmunised population such as a retirement home, where Influenza can be life-threatening. If treatment is started within first 24-48 hours of exposure, it can reduce the duration and severity of symptoms. As in the famous verse "Prevention is better than cure", main mode of prevention in this case is vaccine. Unfortunately no vaccine of Avain Influenza A virus is available for human beings but human influenza vaccine is available, which consists of killed Influenza A and B virus. Human vaccine is usually reformulated each year to contain current antigenic strains of viruses. It is given to people belonging to high-risk categories in the months of September/October and is meant for one particular season only. As for Avian virus, best we can do is to avoid bird company. So, the conclusion that we can draw from this discussion is that Influenza (human flu as well as bird flu) spreads essentially by micro-droplets. There is absolutely no harm in eating eggs and meat. Therefore, it is advised not to raise unnecessary alarm among population. DR KHALID MAHMOOD SHOUQ (D.V.M) http://www.masterytv.biz/agrilive http://www.mybiznas.com/agrilive EDITOR IN CHIEF THE VETERINARY NEWS & VIEWS [WEEKLY] 392-A, SAMANABAD FAISALABAD, PAKISTAN TEL.0092 41 665392FAX, 0092 41 665392 MOBILE, 0300 6620616-0303 6711581-82 E-MAIL: newsviews@bremail.com HTTP.pakissan.com http://www.freegb.net/readbook.cgi?24311 This article is from World Veterinary Association   http://worldvet.org/ The URL for this story is:   http://worldvet.org/modules.php?op=modload&name=News&file=article&sid=1650