SWINE FLU , ALERT !
The swine flu virus that has infected almost 6,500 people in 33 countries is not the product of a lab accident, World Health Organization officials declared yesterday.
The health officials were arguing against a hypothesis that emerged earlier this week. An Australian researcher named Adrian Gibbs who was has been involved in the development of antiviral flu drugs issued a report suggesting the new strain may have accidentally evolved in eggs scientists use to grow viruses and drugmakers use to make vaccines. Gibbs said he came to his conclusion as part of an effort to trace the virus’s origins by analyzing its genetic blueprint. “One of the simplest explanations is that it’s a laboratory escape,” Gibbs said…. “But there are lots of others” [Bloomberg]. Gibbs said this new virus had evolved faster than other flu viruses found in pigs, which he said suggested that it combined with other viruses being used in a lab. He argued that the virus could have then escaped into the general population.
But at a press conference, WHO official Keiji Fukuda announced that the hypothesis had been investigated and rejected. “Based on that evaluation by all of the laboratories, the conclusion is that this group of scientists feels that the hypothesis does not really stand up to scrutiny,” Dr. Fukuda said. “The evidence suggests that this is a naturally occurring virus and not a laboratory-derived virus” [MedScape]. He did not go into specifics of the investigation, but did say that the virus’s mutation rate was typical.
A flu virus is constantly evolving in subtle ways, and can sometimes mutate dramatically because its genes are on eight separate strands, or “gene segments.” One or two or more can be replaced, like cards in draw poker. That’s a rare event, however, and requires that two flu strains invade a single cell, replicate and then get their products mixed up in the packaging. The result is a virus dramatically different in immunological appearance, and sometimes in disease-causing capability, from either parent [Washington Post]. Somehow, the H1N1 that health officials are grappling with did shuffle its genetic cards in such a fashion, combining genes from North American and Eurasian pig viruses.
WHO officials also announced yesterday that scientists will need more time to decide whether to start mass production of vaccines against the swine flu virus…. Fukuda said production of vaccines against the new virus could disrupt production of seasonal flu vaccines and so needed careful thoughtnfluenza (flu) is infection of the lungs and airways with one of the influenza viruses. It causes a fever, runny nose, sore throat, cough, headache, muscle aches (myalgias), and a general feeling of illness (malaise).
Every year, throughout the world, widespread outbreaks of influenza occur during late fall or early winter. Influenza occurs in epidemics, in which many people get sick all at once. Influenza epidemics may occur in two waves: first in schoolchildren and the people who live with them and, second, in people who are confined to home or live in long-term care facilities, mainly older people. In each epidemic, usually only one strain of influenza virus is responsible for the disease. The name of a strain often reflects where it was first found: a location (for example, Hong Kong flu) or an animal (for example, swine flu).
There are two types of influenza virus, type A and type B, and many different strains within each type. About 95% of influenza cases are caused by influenza virus type A. The illnesses produced by the different types and strains are similar. The strain of influenza virus causing outbreaks is always changing, so each year the influenza virus is a little different from the previous year's. It often changes enough that previously effective vaccines no longer work.
Influenza is distinctly different from the common cold. It is caused by a different virus and produces symptoms that are more severe. Also, influenza affects cells much deeper down in the respiratory tract.
Influenza virus is spread by inhaling droplets that have been coughed or sneezed out by an infected person or by having direct contact with an infected person's nasal secretions. Handling household articles that have been in contact with an infected person or an infected person's secretions may sometimes spread the disease.
Symptoms and Diagnosis
Symptoms start 1 to 4 days after infection and can begin suddenly. Chills or a chilly sensation is often the first indication. Fever is common during the first few days, sometimes reaching 102 to 103° F (about 39° C). Many people feel so ill, weak, and tired that they remain in bed for days. They have aches and pains throughout the body, particularly in the back and legs. Headache is often severe, with aching around and behind the eyes. Bright light may make the headache worse.
At first, respiratory symptoms may be relatively mild. They may include a scratchy sore throat, a burning sensation in the chest, a dry cough, and a runny nose. Later, the cough can become severe and bring up phlegm (sputum). The skin may be warm and flushed, especially on the face. The mouth and throat may redden, the eyes may water, and the whites of the eyes may become bloodshot. People, especially children, may have nausea and vomiting. A few people lose their sense of smell for a few days or weeks. Rarely, the loss is permanent.
Most symptoms subside after 2 or 3 days. However, fever sometimes lasts up to 5 days. Cough, weakness, sweating, and fatigue may persist for several days or occasionally weeks. Mild airway irritation, which can result in a decrease in how long or hard a person can exercise, or slight wheezing may take 6 to 8 weeks to completely resolve.
The most common complication of influenza is pneumonia, which can be viral, bacterial, or both. In viral pneumonia, the influenza virus itself spreads into the lungs. In bacterial pneumonia, unrelated bacteria (such as pneumococci or staphylococci) attack the person's weakened defenses. With either, people may have a worsened cough, difficulty breathing, persistent or recurring fever, and sometimes blood or pus in the sputum. Pneumonia is more common among older people and among people with a heart or lung disorder. In long-term care facilities, as many as 7% of older people who develop influenza have to be hospitalized, and 1 to 4% die. Younger people with a chronic disorder are also at risk of developing severe complications.
Because most people are familiar with the symptoms of influenza and because influenza occurs in epidemics, it is often correctly diagnosed by the person who has it or by family members. The severity of symptoms and the presence of a high fever and body aches help distinguish influenza from a cold, especially when the illness occurs during an influenza outbreak. It is more difficult to correctly identify influenza by symptoms alone when no outbreak is occurring. Tests on samples of blood or respiratory secretions can be used to identify the influenza virus. Such tests are done mainly when people appear very ill or when a doctor suspects another cause for the symptoms. Some tests can be done in the doctor's office.
Prevention
Annual vaccination is the best way to avoid getting influenza. Influenza vaccines contain inactivated (killed) influenza virus or pieces of the virus and are given by injection. A newer vaccine, inhaled as a nasal spray, contains weakened live viruses. This vaccine is used only in healthy people aged 5 to 49 years. Influenza vaccines usually protect against three different strains of influenza virus. Different vaccines may be given every year to keep up with changes in the virus. Doctors try to predict the strain of virus that will attack each year based on the strain of virus that predominated during the previous influenza season and the strain causing disease in other parts of the world.
Vaccination is useful for most people but is particularly important for people who are likely to become very ill if infected. These people include the young (particularly those younger than 24 months), those older than 65, those with a weakened immune system, and those with a chronic disorder such as diabetes or a lung, heart, or kidney disorder. In older people who live in long-term care facilities, the vaccine is less likely to prevent influenza, but it reduces the chances of developing pneumonia and of dying. Other than occasional soreness at the injection site, side effects from the vaccine are rare.
In the United States, vaccination takes place during the fall so that levels of antibodies are highest during the peak influenza months: November through March. For most people, about 2 weeks is needed for the vaccination to provide protection.
Several antiviral drugs can be used to prevent infection with influenza virus. Doctors may prescribe these drugs when people have had a clear, recent exposure to someone with influenza. These drugs are also given to people who have conditions that make vaccination ineffective or dangerous. The drugs are used during epidemics of influenza to protect unvaccinated people who are at high risk of complications of influenza: older people and people with a chronic disorder.
Amantadine Some Trade Names
SYMMETREL
and rimantadine Some Trade Names
FLUMADINE
are older antiviral drugs that provide protection against influenza type A but not influenza type B. These drugs can cause stomach upset, nervousness, sleeplessness, and other side effects, especially in older people and in those with a brain or kidney disorder. Rimantadine Some Trade Names
FLUMADINE
tends to have fewer side effects than amantadine Some Trade Names
SYMMETREL
. Another drawback of both amantadine Some Trade Names
SYMMETREL
and rimantadine Some Trade Names
FLUMADINE
is that the influenza virus rapidly develops resistance to them. During the 2005 to 2006 influenza season, concerns about resistance prompted the Centers for Disease Control and Prevention to discourage the use of these drugs for prevention and treatment. Two newer drugs, oseltamivir Some Trade Names
TAMIFLU
and zanamivir Some Trade Names
RELENZA
, can prevent infection with influenza virus type A or type B. These drugs have minimal side effects.
Treatment
The main treatment for influenza is to rest adequately, drink plenty of fluids, and avoid exertion. Normal activities may resume 24 to 48 hours after the body temperature returns to normal, but most people take several more days to recover. People may treat fever and aches with acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs, such as aspirin or ibuprofen Because of the risk of Reye's syndrome, children should not be given aspirin Some Trade Names
ECOTRIN
ASPERGUM
. Acetaminophen and ibuprofen Some Trade Names
ADVIL
MOTRIN
NUPRIN
can be used in children if needed. Other measures as listed for the common cold, such as nasal decongestants and steam inhalation, may help relieve symptoms.
The same antiviral drugs that prevent infection ( amantadine Some Trade Names
SYMMETREL
, rimantadine , oseltamivir , and zanamivir Some Trade Names
RELENZA
are also helpful in treating people who have influenza. However, these drugs work only if taken in the first day or two after symptoms begin, and they shorten the duration of fever and respiratory symptoms only by a day or so. Nevertheless, these drugs are very effective in some people. Most doctors recommend zanamivir Some Trade Names
RELENZA
or oseltamivir , which are effective against both influenza type A and type B. If a secondary bacterial infection develops, antibiotics are added.
Pandemic influenza is the greatest public health threat our society faces. Yet we're barely aware of the history of the great pandemic of 1918—which is why this new account is especially timely
source Laborary Merck
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