Avian influenza

Avian influenza — known informally as avian flu or bird flu — refers to "influenza caused by viruses adapted to birds."[clarification needed] Of the greatest concern is highly pathogenic avian influenza (HPAI).

"Bird flu" is a phrase similar to "swine flu," "dog flu," "horse flu," or "human flu" in that it refers to an illness caused by any of many different strains of influenza viruses that have adapted to a specific host. All known viruses that cause influenza in birds belong to the species influenza A virus. All subtypes (but not all strains of all subtypes) of influenza A virus are adapted to birds, which is why for many purposes avian flu virus is the influenza A virus. (Note, however, that the "A" does not stand for "avian").

Adaptation is not exclusive. Being adapted towards a particular species does not preclude adaptations, or partial adaptations, towards infecting different species. In this way, strains of influenza viruses are adapted to multiple species, though may be preferential towards a particular host. For example, viruses responsible for influenza pandemics are adapted to both humans and birds. Recent influenza research into the genes of the Spanish flu virus shows it to have genes adapted to both birds and humans, with more of its genes from birds than less deadly later pandemic strains.

While its most highly pathogenic strain (H5N1) had been spreading throughout Asia since 2003, avian influenza reached Europe in 2005, and the Middle East, as well as Africa, the following year. On January 22, 2012, China reported its second bird flu death in a month following other fatalities in Vietnam and Cambodia.

Genetics
Genetic factors in distinguishing between "human flu viruses" and "avian flu viruses" include:
PB2: (RNA polymerase): Amino acid (or residue) position 627 in the PB2 protein encoded by the PB2 RNA gene. Until H5N1, all known avian influenza viruses had a Glu at position 627, while all human influenza viruses had a Lys.
HA: (hemagglutinin): Avian influenza HA viruses bind alpha 2-3 sialic acid receptors, while human influenza HA viruses bind alpha 2-6 sialic acid receptors. Swine influenza viruses have the ability to bind both types of sialic acid receptors. Hemagglutinin is the major antigen of the virus against which neutralizing antibodies are produced, and influenza virus epidemics are associated with changes in its antigenic structure. This was originally derived from pigs, and should technically be referred to as "pig flu" 



Contraction/spreading of avian influenza
Most human contractions of the avian flu are a result of either handling dead infected birds or from contact with infected fluids. While most wild birds mainly have only a mild form of the H5N1 strain, once domesticated birds such as chickens or turkeys are infected, it could become much more deadly because the birds are often within close contact of one another. There is currently a large threat of this in Asia with infected poultry due to low hygiene conditions and close quarters . Although it is easy for humans to become infected from birds, it's much more difficult to do so from human to human without close and lasting contact.

Spreading of H5N1 from Asia to Europe is much more likely caused by both legal and illegal poultry trades than dispersing through wild bird migrations, being that in recent studies, there were no secondary rises in infection in Asia when wild birds migrate south again from their breeding grounds. Instead, the infection patterns followed transportation such as railroads, roads, and country borders, suggesting poultry trade as being much more likely. While there have been strains of avian flu to exist in the United States, such as Texas in 2004, they have been extinguished and have not been known to infect humans.

Influenza pandemic
Further information: Influenza pandemic

Pandemic flu viruses have some avian flu virus genes and usually some human flu virus genes. Both the H2N2 and H3N2 pandemic strains contained genes from avian influenza viruses. The new subtypes arose in pigs coinfected with avian and human viruses, and were soon transferred to humans. Swine were considered the original "intermediate host" for influenza, because they supported reassortment of divergent subtypes. However, other hosts appear capable of similar coinfection (e.g., many poultry species), and direct transmission of avian viruses to humans is possible. The Spanish flu virus strain may have been transmitted directly from birds to humans. In spite of their pandemic connection, avian influenza viruses are noninfectious for most species. When they are infectious, they are usually asymptomatic, so the carrier does not have any disease from it. Thus, while infected with an avian flu virus, the animal does not have a "flu". Typically, when illness (called "flu") from an avian flu virus does occur, it is the result of an avian flu virus strain adapted to one species spreading to another species (usually from one bird species to another bird species). So far as is known, the most common result of this is an illness so minor as to be not worth noticing (and thus little studied). But with the domestication of chickens and turkeys, humans have created species subtypes (domesticated poultry) that can catch an avian flu virus adapted to waterfowl and have it rapidly mutate into a form that kills over 90% of an entire flock in days, can spread to other flocks and kill 90% of them, and can only be stopped by killing every domestic bird in the area. Until H5N1 infected humans in the 1990s, this was the only reason avian flu was considered important. Since then, avian flu viruses have been intensively studied; resulting in changes in what is believed about flu pandemics, changes in poultry farming, changes in flu vaccination research, and changes in flu pandemic planning.

H5N1 has evolved into a flu virus strain that infects more species than any previously known strain, is deadlier than any previously known strain, and continues to evolve, becoming both more widespread and more deadly. This caused Robert G. Webster, a leading expert on avian flu, to publish an article titled "The world is teetering on the edge of a pandemic that could kill a large fraction of the human population" in American Scientist. He called for adequate resources to fight what he sees as a major world threat to possibly billions of lives. Since the article was written, the world community has spent billions of dollars fighting this threat with limited success. H5N1 continues following the principles of evolutionary biology - which seems ignored or misunderstood by Webster, remaining primarily a poultry disease and without the social conditions necessary for a severe human flu pandemic.

Vaccines have been formulated against several of the avian H5N1 influenza varieties. Vaccination of poultry against the ongoing H5N1 epizootic is widespread in certain countries. Some vaccines also exist for use in humans, and others are in testing, but none have been made available to civilian populations, nor are produced in quantities sufficient to protect more than a tiny fraction of the Earth's population in the event of an H5N1 pandemic outbreak. The World Health Organization has compiled a list of known clinical trials of pandemic influenza prototype vaccines, including those against H5N1.

H5N1
Further information: Influenza A virus subtype H5N1 and Transmission and infection of H5N1

The highly pathogenic influenza A virus subtype H5N1 is an emerging avian influenza virus that has been causing global concern as a potential pandemic threat. It is often referred to simply as "bird flu" or "avian influenza", even though it is only one subtype of avian influenza-causing virus.

H5N1 has killed millions of poultry in a growing number of countries throughout Asia, Europe and Africa. Health experts are concerned that the coexistence of human flu viruses and avian flu viruses (especially H5N1) will provide an opportunity for genetic material to be exchanged between species-specific viruses, possibly creating a new virulent influenza strain that is easily transmissible and lethal to humans. The mortality rate for humans with H5N1 is 60%.

Since the first H5N1 outbreak occurred in 1987, there has been an increasing number of HPAI H5N1 bird-to-human transmissions, leading to clinically severe and fatal human infections. Because a significant species barrier exists between birds and humans, though, the virus does not easily cross over to humans, though some cases of infection are being researched to discern whether human to human transmission is occurring. More research is necessary to understand the pathogenesis and epidemiology of the H5N1 virus in humans. Exposure routes and other disease transmission characteristics, such as genetic and immunological factors that may increase the likelihood of infection, are not clearly understood.

On January 18, 2009, a 27-year-old woman from eastern China died of bird flu, Chinese authorities said, making her the second person to die from the deadly virus at that time. Two tests on the woman were positive for H5N1 avian influenza, said the ministry, which did not say how she might have contracted the virus.

Although millions of birds have become infected with the virus since its discovery, 306 humans have died from the H5N1 in twelve countries according to WHO data as of February 2, 2011.

The avian flu claimed at least 300 humans in Azerbaijan, Cambodia, China, Egypt, Indonesia, Iraq, Laos, Nigeria, Pakistan, Thailand, Turkey, and Vietnam. Epidemiologists are afraid the next time such a virus mutates, it could pass from human to human; however, the current A/H5N1 virus does not transmit easily from human to human. If this form of transmission occurs, another pandemic could result. Thus, disease-control centers around the world are making avian flu a top priority. These organizations encourage poultry-related operations to develop a preemptive plan to prevent the spread of H5N1 and its potentially pandemic strains. The recommended plans center on providing protective clothing for workers and isolating flocks to prevent the spread of the virus.

The Thailand outbreak of avian flu caused massive economic losses, especially among poultry workers. Infected birds were culled and sacrificed. The public lost confidence with the poultry products, thus decreasing the consumption of chicken products. This also elicited a ban from importing countries. There were, however, factors which aggravated the spread of the virus, including bird migration, cool temperature (increases virus survival) and several festivals at that time.

In domestic animals
Several domestic species have been infected with and shown symptoms of H5N1 viral infection,including cats, dogs, ferrets, pigs,and birds.


Birds
Attempts are made in the United States to minimize the presence of HPAI in poultry thorough routine surveillance of poultry flocks in commercial poultry operations. Detection of a HPAI virus may result in immediate culling of the flock. Less pathogenic viruses are controlled by vaccination, which is done primarily in turkey flocks (ATCvet codes: QI01AA23 for the inactivated fowl vaccine, QI01CL01 for the inactivated turkey combination vaccine).


Seals
A recent strain of the virus is able to infect the lungs of seals.

Chronic fatigue syndrome

Chronic fatigue syndrome (CFS) is the most common name used to designate a significantly debilitating medical disorder or group of disorders generally defined by persistent fatigue accompanied by other specific symptoms for a minimum of six months in adults (and 3 months in children/adolescents), not due to ongoing exertion, not substantially relieved by rest, nor caused by other medical conditions. The disorder may also be referred to as myalgic encephalomyelitis (ME), post-viral fatigue syndrome (PVFS), chronic fatigue immune dysfunction syndrome (CFIDS), or several other terms. Biological, genetic, infectious and psychological mechanisms have been proposed for the development and persistence of symptoms but the etiology of CFS is not understood and may have multiple causes. There is no diagnostic laboratory test or biomarker for CFS.

Symptoms of CFS include post-exertional malaise; unrefreshing sleep; widespread muscle and joint pain; sore throat; headaches of a type not previously experienced; cognitive difficulties; chronic, often severe, mental and physical exhaustion; and other characteristic symptoms in a previously healthy and active person. Persons with CFS may report additional symptoms including muscle weakness, increased sensitivity to light, sounds and smells, orthostatic intolerance, digestive disturbances, depression, and cardiac and respiratory problems. It is unclear if these symptoms represent co-morbid conditions or are produced by an underlying etiology of CFS. CFS symptoms vary from person to person in number, type, and severity.

Fatigue is a common symptom in many illnesses, but CFS is comparatively rare. Estimates of CFS prevalence vary widely, from 7 to 3,000 cases of CFS for every 100,000 adults, but national health organizations have estimated more than 1 million Americans and approximately a quarter of a million people in the UK have CFS. CFS occurs more often in women than men, and is less prevalent among children and adolescents. The quality of life is "particularly and uniquely disrupted" in CFS.

There is agreement on the genuine threat to health, happiness and productivity posed by CFS, but various physicians' groups, researchers and patient advocates promote different nomenclature, diagnostic criteria, etiologic hypotheses and treatments, resulting in controversy about many aspects of the disorder. The name "chronic fatigue syndrome" itself is controversial as many patients and advocacy groups, as well as some experts, believe the name trivializes the medical condition and want the name changed.

Classification

Notable definitions include:

• CDC definition (1994)—the most widely used clinical and research description of CFS, it is also called the Fukuda definition and was based on the Holmes or CDC 1988 scoring system. The 1994 criteria require the presence of four or more symptoms beyond fatigue, where the 1988 criteria require six to eight.
• The Oxford criteria (1991)—includes CFS of unknown etiology and a subtype called post-infectious fatigue syndrome (PIFS). Important differences are that the presence of mental fatigue is necessary to fulfill the criteria and symptoms are accepted that may suggest a psychiatric disorder.
• The 2003 Canadian Clinical working definition[— states that "A patient with ME/CFS will meet the criteria for fatigue, post-exertional malaise and/or fatigue, sleep dysfunction, and pain; have two or more neurological/cognitive manifestations and one or more symptoms from two of the categories of autonomic, neuroendocrine, and immune manifestations; and [the illness will persist for at least 6 months]".

The different case definitions used to research the illness may influence the types of patients selected for studies, and research also suggests subtypes of patients exist within the heterogeneous illness.

Clinical practice guidelines—with the aim of improving diagnosis, management, and treatment—are generally based on case descriptions. An example is the CFS/ME guideline for the National Health Service in England and Wales, produced in 2007 by the National Institute for Health and Clinical Excellence (NICE).

Naming

Chronic fatigue syndrome is the most commonly used designation, but widespread approval of a name is lacking. Different authorities on the illness view CFS as a central nervous system, metabolic, infectious or post-infectious, cardiovascular, immune system or psychiatric disorder, and different symptom profiles may be caused by various disorders.

Over time and in different countries many names have been associated with the condition(s). Aside from CFS, some other names used include Akureyri disease, benign myalgic encephalomyelitis, chronic fatigue immune dysfunction syndrome, chronic infectious mononucleosis, epidemic myalgic encephalomyelitis, epidemic neuromyasthenia, Iceland disease, myalgic encephalomyelitis, myalgic encephalitis, myalgic encephalopathy, post-viral fatigue syndrome, raphe nucleus encephalopathy, Royal Free disease, Tapanui flu and yuppie flu (considered pejorative). Many patients would prefer a different name such as "myalgic encephalomyelitis", believing the name "chronic fatigue syndrome" trivializes the condition, prevents it from being seen as a serious health problem, and discourages research.

A 2001 review referenced myalgic encephalomyelitis symptoms in a 1959 article by Acheson, stating ME could be a distinct syndrome from CFS, but in literature the two terms are generally seen as synonymous. A 1999 review explained the Royal Colleges of Physicians, Psychiatrists, and General Practitioners in 1996 advocated the use of chronic fatigue syndrome instead of myalgic encephalomyelitis or ME which was in wide use in the United Kingdom, "because there is, so far, no recognized pathology in muscles and in the central nervous system as is implied by the term ME." An editorial noted that the 1996 report received some acceptance, but also criticism from those advocating the use of different naming conventions, suggesting the report was biased, dominated by psychiatrists, and that dissenting voices were excluded. In 2002, a Lancet commentary noted the recent report by the "Working Group on CFS/ME" used the compromise name CFS/ME stating, "The fact that both names for the illness were used symbolises respect for different viewpoints whilst acknowledging the continuing lack of consensus on a universally acceptable name."

Signs and symptoms

Onset

The majority of CFS cases start suddenly, usually accompanied by a "flu-like illness" while a significant proportion of cases begin within several months of severe adverse stress. An Australian prospective study found that after infection by viral and non-viral pathogens, a sub-set of individuals met the criteria for CFS, with the researchers concluding that "post-infective fatigue syndrome is a valid illness model for investigating one pathophysiological pathway to CFS". However, accurate prevalence and exact roles of infection and stress in the development of CFS are currently unknown.

Symptoms

The most commonly used diagnostic criteria and definition of CFS for research and clinical purposes were published by the United States Centers for Disease Control and Prevention (CDC). The CDC recommends the following three criteria be fulfilled:

1. A new onset (not lifelong) of severe fatigue for six consecutive months or greater duration which is unrelated to exertion, is not substantially relieved by rest, and is not a result of other medical conditions.
2. The fatigue causes a significant reduction of previous activity levels.
3. Four or more of the following symptoms that last six months or longer:

• Impaired memory or concentration
• Post-exertional malaise, where physical or mental exertions bring on "extreme, prolonged exhaustion and sickness"
• Unrefreshing sleep
• Muscle pain (myalgia)
• Pain in multiple joints (arthralgia)
• Headaches of a new kind or greater severity
• Sore throat, frequent or recurring
• Tender lymph nodes (cervical or axillary)
• Other common symptoms include:
• Irritable bowel, abdominal pain, nausea, diarrhea or bloating
• Chills and night sweats
• Brain fog
• Chest pain
• Shortness of breath
• Chronic cough
• Visual disturbances (blurring, sensitivity to light, eye pain or dry eyes)
• Allergies or sensitivities to foods, alcohol, odors, chemicals, medications or noise
• Difficulty maintaining upright position (orthostatic instability, irregular heartbeat, dizziness, balance problems or fainting)
• Psychological problems (depression, irritability, mood swings, anxiety, panic attacks)

The CDC proposes that persons with symptoms resembling those of CFS consult a physician to rule out several treatable illnesses: Lyme disease, "sleep disorders, depression, alcohol/substance abuse, diabetes, hypothyroidism, mononucleosis (mono), lupus, multiple sclerosis (MS), chronic hepatitis and various malignancies." Medications can also cause side effects that mimic symptoms of CFS.

Functioning
People report critical reductions in levels of physical activity and a reduction in the complexity of activity has been observed, with reported impairment comparable to other fatiguing medical conditions including late-stage AIDS, lupus, rheumatoid arthritis, chronic obstructive pulmonary disease (COPD), and end-stage renal disease. CFS affects a person's functional status and well-being more than major medical conditions such as multiple sclerosis, congestive heart failure, or type II diabetes mellitus. The severity of symptoms and disability is the same in both genders with strongly disabling chronic pain,[ but despite a common diagnosis the functional capacity of individuals with CFS varies greatly. While some lead relatively normal lives, others are totally bed-ridden and unable to care for themselves. Employment rates vary with over half unable to work and nearly two-thirds limited in their work because of their illness. More than half were on disability benefits or temporary sick leave, and less than a fifth worked full-time.


Cognitive functioning
A 2010 meta-analysis concluded cognitive symptoms were principally resultants of decreased attention, memory, and reaction time. The deficits were in the range of 0.5 to 1.0 standard deviations below expected and were judged likely to affect day-to-day activities. Simple and complex information processing speed and functions entailing working memory over long time periods were moderately to extensively impaired. These deficits are generally consistent with those reported by patients. Perceptual abilities, motor speed, language, reasoning, and intelligence did not appear to be significantly altered.

Treatment
Many people do not fully recover from CFS even with treatment. Cognitive behavioural therapy (CBT) and graded exercise therapy (GET) have shown moderate effectiveness for many people in multiple randomized controlled trials. As many of the CBT and GET studies required visits to a clinic, those severely affected may not have been included. Two large surveys of patients indicated that pacing is the most helpful intervention, or is considered useful by 96% of participants. Medication plays a minor role in management. No intervention has been proven effective in restoring the ability to work.


Cognitive behavioral therapy

Cognitive behavioral therapy, a form of psychological therapy often used to treat chronically ill patients, is a moderately effective treatment for CFS that "can be useful in treating some CFS patients." Since the cause or causes of CFS are unknown, CBT tries to help patients understand their individual symptoms and beliefs and develop strategies to improve day-to-day functioning whatever the cause of the symptoms. CBT is also thought to help patients by removing unhelpful illness beliefs which may perpetuate the illness.

A Cochrane Review meta-analysis of 15 randomized, controlled cognitive behavioral therapy trials with 1043 participants concluded that CBT was an effective treatment to reduce the symptom of fatigue. Four reviewed studies showed that CBT resulted in a clinical response for 40% of participants vs 26% of those treated with "usual care". Similarly, in three studies CBT worked better than other types of psychological therapies (48% vs 27%). The effects may diminish after a course of therapy is completed; the reviewers write that "the evidence base at follow-up is limited to a small group of studies with inconsistent findings" and encourage further studies. A 2007 meta-analysis of 5 CBT randomized controlled trials of chronic fatigue and chronic fatigue syndrome reported 33-73% of the patients improved to the point of no longer being clinically fatigued. A 2010 meta-analysis of trials that measured physical activity before and after CBT showed that although CBT effectively reduced fatigue, activity levels were not affected by CBT and changes in physical activity were not related to changes in fatigue. They conclude that the effect of CBT on fatigue is not mediated by a change in physical activity.

CBT has been criticised by patients' organisations because of negative reports from some of their members that have indicated that CBT can sometimes make people worse, a common result across multiple patient surveys.

Graded exercise therapy
Graded exercise therapy is a form of physical therapy. A meta-analysis published in 2004 of five randomized trials found that patients who received exercise therapy were less fatigued after 12 weeks than the control participants, and the authors cautiously conclude that GET shows promise as a treatment. However, after 6 months the benefit became non-significant compared to the control group who did not receive GET, and functional work capacity was not significantly improved after therapy. A systematic review published in 2006 included the same five RCTs, noting that "no severely affected patients were included in the studies of GET". Surveys conducted on behalf of patient organizations commonly report adverse effects.

To avoid detrimental effects from GET, care must be taken to avoid the exacerbation of symptoms while catering the program to individual capabilities and the fluctuating nature of symptoms.


Pacing
Pacing is an energy management strategy based on the observation that symptoms of the illness tend to increase following minimal exertion. There are two forms: symptom-contingent pacing, where the decision to stop (and rest or change an activity) is determined by an awareness of an exacerbation of symptoms; and time-contingent pacing, which is determined by a set schedule of activities which a patient estimates he or she is able to complete without triggering post-exertional malaise (PEM). Thus the principle behind pacing for CFS is to avoid over-exertion and an exacerbation of symptoms. It is not aimed at treating the illness as a whole. Those whose illness appears stable may gradually increase activity and exercise levels but according to the principle of pacing, must rest if it becomes clear that they have exceeded their limits. Some programmes combine symptom and time-contingent approaches. A trial of one such programme reported limited benefits. A larger, randomised controlled trial found that pacing had statistically better results than relaxation/flexibility therapy. A 2009 survey of 828 Norwegian CFS patients found that pacing was evaluated as useful by 96% of the participants.

Top 10 Mysterious Diseases

10) AIDS

Twenty-five years since it was first identified, there is still no cure for Acquired Immune Deficiency Syndrome. AIDS remains among the world's most potent killers, especially in developing countries. The disease likely started with a chimp to human jump, recent research confirmed.


9)Alzheimer's Disease

Not to be confused with the forgetfulness that affects most everyone in their later years, Alzheimer's is a degenerative brain disorder that manifests differently in each of its sufferers. The exact cause isn't understood and it can't be effectively treated.


8)The Common Cold

Even with an estimated one billion cases in the United States every year, doctors still know very little about the nose-running, cough-inducing cold, whose root causes number in the hundreds (some headway is being made). Time and chicken soup, not antibiotics, is often the only prescription that helps.


7)Avian Flu

Humans have no immunity to the powerful flu virus carried by birds, which health official fear could mutate into a strain that can be transmitted between humans. Death rates for human infected are around 50 percent but, so far, humans have been infected mostly by direct handling with infected birds. A recent cluster of cases, however, appeared to involved its spread between people.


6)Pica

People diagnosed with Pica have an insatiable urge to eat non-food substances like dirt, paper, glue and clay. Though it is believed to be linked with mineral deficiency, health experts have found no real cause and no cure for the peculiar disorder.


5)Autoimmune Disorders

A catchall term for a host of afflictions including Lupus and MS, autoimmune disorders treat the body's organs and normal functions as enemy invaders. They're usually chronic, always debilitating, and doctors can do little except ease their symptoms.


4)Schizophrenia

Experts consider this the most puzzling of mental disorders, one which robs the sufferer of the ability to logically distinguish between reality and fantasy. Symptoms range wildly between patients and include delusions, hallucinations, disorganized speech, lack of motivation or emotion, but the disease has no defining medical tests.


3)Creutzfeldt-Jakob Disease

One version of this rare brain disorder is better known "Mad Cow" and can be contracted by eating contaminated beef. "Regular" CJD is also always fatal, quick-acting and is the most common form, but develops in most patients for reasons doctors have yet to figure out and can not prevent.


2)Chronic Fatigue Syndrome

Chronic fatigue is a classic MUPS (medically unexplained physical symptoms) disease, with a diagnosis based only on the ruling out of other possibilities. More than just feeling a little tired, CFS patients are often bed-ridden for days at a time.


1)Morgellons Disease

This mysterious illness, which has cropped up again recently, displays almost sci-fi symptoms. Sufferers complain of intensely creepy-crawly skin and odd fibrous strands which protrude from open wounds. Some in the medical community blame the "disease" on psychotic delusion, but others say the symptoms are very real.