Embed Size (px)
Citation preview
Influenza (the flu)Influenza (the flu)
By
Salwa Hassan Teama
Ain Shams University
A cold is a milder respiratory illness than the flu. While cold symptoms can make you feel bad for a few days. Flu symptoms can make you feel quite ill for a few days to weeks.
Cold symptoms usually begin with a sore throat, which usually goes away after a day or two. Nasal symptoms, runny nose, and congestion follow, along with a cough by the fourth and fifth days. Fever is uncommon in adults, but a slight fever is possible. Children are more likely to have a fever with a cold.With cold symptoms, your nose teems with watery nasal secretions for the first few days. Later, these become thicker and darker.
Whether a person has typical seasonal flu or swine flu, the symptoms seem to be quite similar. Flu symptoms are usually more severe than cold symptoms and come on quickly. Symptoms of swine flu and seasonal flu include sore throat, fever, headache, muscle aches and soreness, congestion, and cough. Swine flu in particular is also associated with vomiting and diarrhea.
Difference Between Cold or FLU
Influenza (the flu) is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to death. The best way to prevent seasonal flu is by getting a seasonal flu vaccination each year. •In virus classification influenza viruses are RNA viruses that make up three of the five genera of the family Orthomyxoviridae. Influenzavirus A Influenzavirus B Influenzavirus C
Influenza (the flu)
Influenza A virus
•The type A viruses are the most virulent human pathogens among the three influenza types and cause the most severe disease. Type A flu or influenza A viruses are capable of infecting people as well as animals.
•Wild aquatic birds are the natural hosts for a large variety of influenza A.
•The influenza A virus can be subdivided into different serotypes based on the antibody response to these viruses. The serotypes that have been confirmed in humans, ordered by the number of known human pandemic deaths, are:•H1N1, which caused Spanish flu in 1918, and the 2009 flu pandemic •H2N2, which caused Asian Flu in 1957 •H3N2, which caused Hong Kong Flu in 1968 •H5N1, a current pandemic threat •H7N7, which has unusual zoonotic potential•H1N2, endemic in humans and pigs •H9N2 •H7N2 •H7N3 •H10N7
Influenza B virus
Influenza B almost exclusively infects humans and is less common than influenza A. This type of influenza mutates at a rate 2–3 times lower than type A. This reduced rate of antigenic change, combined with its limited host range ensures that pandemics of influenza B do not occur.
Influenza virus C
Influenza C virus, which infects humans, dogs and pigs, sometimes causing both severe illness and local epidemics. However, influenza C is less common than the other types and usually only causes mild disease in children.
•Influenzaviruses A, B and C are very similar in overall structure. The virus particle is 80–120 nanometres in diameter and usually roughly spherical, although filamentous forms can occur. These filamentous forms are more common in influenza C, which can form cordlike structures up to 500 micrometres long on the surfaces of infected cells.
Structure
The viral particles of all influenza Viruses are similar in composition. These are made of a viral envelope containing two main types of glycoproteins, wrapped around a central core. The central core contains the viral RNA genome and other viral proteins that package and protect this RNA.
RNA tends to be single stranded but in special cases it is double. Unusually for a virus, its genome is not a single piece of nucleic acid; instead, it contains seven or eight pieces of segmented negative-sense RNA, each piece of RNA contains either one or two genes. For example, the influenza A genome contains 11 genes on eight pieces of RNA, encoding for 11 proteins: hemagglutinin (HA), neuraminidase (NA), nucleoprotein (NP), M1, M2, NS1, NS2(NEP), PA, PB1, PB1-F2 and PB2
Hemagglutinin (HA) and neuraminidase (NA) are the two large glycoproteins on the outside of the viral particles. HA is a lectin that mediates binding of the virus to target cells and entry of the viral genome into the target cell, while NA is involved in the release of progeny virus from infected cells, by cleaving sugars that bind the mature viral particles.
Thus, these proteins are targets for antiviral drugs. Furthermore, they are antigens to which antibodies can be raised.
Hemagglutinin & Neuraminidase
•Influenza A viruses are classified into subtypes based on antibody responses to HA and NA. These different types of HA and NA form the basis of the H and N distinctions in, for example, H5N1. There are 16 H and 9 N subtypes known, but only H 1, 2 and 3, and N 1 and 2 are commonly found in humans.
•The most prevalent human flu viruses are H1N1 and H3N2. All of the human versions of H1N1 and H3N2 can easily transmitted from person to person because the H1 and H3 proteins recognize human cell receptors, making it easy for them to split into healthy cells.
Seasonal FluSeasonal flu is the term used to refer to the flu outbreaks that occur yearly, mainly in the late fall and winter.
Pandemic FluPandemic flu refers to particularly virulent strains of flu that spread rapidly from person to person to create a world-wide epidemic (pandemic).
Avian (Bird) Flu The flu virus occurs in wild aquatic birds such as ducks and shore birds. It does not normally spread from birds to humans. However, pigs can be infected by bird influenza (as well as by the form of influenza that affects humans) and can pass on the flu to humans. In 1997, it was discovered that a virulent bird influenza had skipped the pig step and had infected humans directly, causing a number of deaths in Asia.
•Most flu symptoms gradually improve over two to five days, but it's not uncommon to feel run down for a week or more. A common complication of the flu is pneumonia, particularly in the young, elderly, or people with lung or heart problems. If you notice shortness of breath, you should let your doctor know. Another common sign of pneumonia is fever that comes back after having been gone for a day or two.
• Ear infections, •Sinus infections,
•Dehydration, and
•Worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes.
Complications of Flu
Influenza spreads around the world in seasonal epidemics, resulting in the deaths of hundreds of thousands annually — millions in pandemic years. Three influenza pandemics occurred in the 20th century and killed tens of millions of people, with each of these pandemics being caused by the appearance of a new strain of the virus in humans. Often, these new strains appear when an existing flu virus spreads to humans from other animal species, or when an existing human strain picks up new genes from a virus that usually infects birds or pigs. An avian strain named H5N1 raised the concern of a new influenza pandemic, after it emerged in Asia in the 1990s, but it has not evolved to a form that spreads easily between people. In April 2009 a novel flu strain evolved that combined genes from human, pig, and bird flu, initially dubbed "swine flu" and also known as influenza A/H1N1, emerged in Mexico, the United States, and several other nations. The World Health Organization officially declared the outbreak to be a "pandemic" on June 11, 2009 . The WHO's declaration of a pandemic level 6 was an indication of spread, not severity.
Influenza Pandemic
Bird Flu
•Fifteen subtypes of influenza virus are known to infect birds, thus providing an extensive reservoir of influenza viruses potentially circulating in bird populations. To date, all outbreaks of the highly pathogenic form have been caused by influenza A viruses of subtypes H5 and H7.
•The strain of avian flu known as H5N1 has been behind most recent outbreaks of deadly avian flu and has also been responsible for the recent human deaths reported in asia, but there are three prominent subtypes of avian influenza virus and among the three subtypes, influenza AH5,AH7 and AH9, there are several strains with varying degrees of strength.
Low pathogenicity (LPAI) - usually only causing mild respiratory disease in domestic poultry .
High pathogenicity (HPAI) - the more virulent type formerly known as fowl plague which often results in up to a 100% flock mortality.
This reassortment process, known as antigenic “shift”, results in a novel subtype different from both parent viruses. As populations will have no immunity to the new subtype, and as no existing vaccines can confer protection, antigenic shift has historically resulted in highly lethal pandemics..Conditions favorable for the emergence of antigenic shift have long been thought to involve humans living in close proximity to domestic poultry and pigs. Because pigs are susceptible to infection with both avian and mammalian viruses, including human strains, they can serve as a “mixing vessel” for the scrambling of genetic material from human and avian viruses, resulting in the emergence of a novel subtype.
Antigenic “Shift”
Infection Control
The single best way to prevent seasonal flu is to get a seasonal flu vaccination each year. There are two types of flu vaccines:•The "flu shot" : an inactivated vaccine (containing killed virus) that is given with a needle. The seasonal flu shot is approved for use in people 6 months of age and older, including healthy people and people with chronic medical conditions.
•The nasal-spray flu vaccine : a vaccine made with live, weakened flu viruses that do not cause the flu (sometimes called LAIV for "Live Attenuated Influenza Vaccine"). LAIV is approved for use in healthy* people 2-49 years of age who are not pregnant. About two weeks after vaccination, antibodies develop that protect against influenza virus infection. Flu vaccines will not protect against flu-like illnesses caused by non-influenza viruses.A seasonal flu vaccine will not protect you against the new 2009 H1N1 flu. A vaccine against the new H1N1 flu is being produced.
Preventing Seasonal Flu: Get Vaccinated
•Vaccinations have been produced to help fight the spread of influenza A, but because there are so many strains of the virus, vaccinations are not always effective or reliable.
????
•Side effects are expected to be similar to those observed with seasonal influenza vaccines. Common side effects include local reactions at the injection site (soreness, swelling, redness) and possibly some systemic reactions (fever, headache, muscle or joint aches). In almost all vaccine recipients, these symptoms are mild, self-limited and last 1-2 days. However, even very large clinical trials will not be able to identify possible rare events that can occur when pandemic vaccines are administered to many millions of people. Further testing of safety andeffectiveness will need to take place after administration of the vaccine. www.who.int/csr/disease/swineflu
Vaccine safety
What happened during the last swine flu pandemic in 1976?
•The 1976 Swine Flu Vaccine caused Guillain-Barré Syndrome; a crippling paralysis that can be fatal if not treated quickly.
•Media now reporting that there was an unproven link to GBS, BUT the acting head of the CDC's Immunization Safety Office, Dr. John Iskander said in Feb. 2008 "A proven association between the 1976-1977 swine influenza vaccine and Guillain-Barré syndrome.
http://www.wepapers.com/Papers/69348/Swine_Flu_The_virus_and_the_mass_vaccination_campaign.ppt , Are the vaccines safe? What you absolutely must know before you take the swine flu vaccine (or any other vaccine).
Treatment
•Treatment with oseltamivir (trade name Tamiflu®) or zanamivir (trade name Relenza®) is recommended for all people with suspected or confirmed influenza who require hospitalization.
Most people ill with influenza will recover without complications. Some people are at highest risk of influenza-related complications and are prioritized for treatment with influenza antiviral drugs this season. They include:
•People with more severe illness, such as those hospitalized with suspected or confirmed influenza •People with suspected or confirmed influenza who are at higher risk for complications
•Children younger than 2 years old •Adults 65 years and older •Pregnant women •People with certain chronic medical or immunosuppressive conditions
•People younger than 19 years of age who are receiving long-term aspirin therapy
Who is prioritized for treatment with influenza antiviral drugs?
References & Update
•http://www.who.int/csr/disease/avian_influenza/en•http://www.cdc.gov/flu/about/disease/•http://www.wepapers.com/Papers/69348/Swine_Flu_The_virus_and_the_mass_vaccination_campaign.ppt, Are the vaccines safe?What you absolutely must know before you take the swine flu vaccine (or any other vaccine).•www.SwineFluShots.us
