Influenza

(Flu, influenza virus)

Influenza is a viral respiratory infection that causes fever, runny nose, cough, headache and malaise. During seasonal epidemics can cause deaths, especially among high-risk patients (eg, people in closed institutions, with high or low age, with cardiovascular insufficiency or in late pregnancy.); during pandemics healthy young patients die themselves. The diagnosis is usually made clinically and is based on local epidemiological patterns. Everyone aged ? 6 months should receive an annual influenza vaccination. Antiviral treatment reduces the duration of illness by about one day, and should be specifically considered for high-risk patients into consideration.

The term refers to influenza disease caused by influenza viruses, but it is also widely and used incorrectly to refer to diseases that are similar run and caused by other viral respiratory pathogens. Influenza viruses are classified by their nucleotide and matrix proteins in the types A, B and C. Infection with the influenza C virus does not result in a typical influenza illness and is not discussed here.

Influenza is a viral respiratory infection that causes fever, runny nose, cough, headache and malaise. During seasonal epidemics can cause deaths, especially among high-risk patients (eg, people in closed institutions, with high or low age, with cardiovascular insufficiency or in late pregnancy.); during pandemics healthy young patients die themselves. The diagnosis is usually made clinically and is based on local epidemiological patterns. Everyone aged ? 6 months should receive an annual influenza vaccination. Antiviral treatment reduces the duration of illness by about one day, and should be specifically considered for high-risk patients into consideration. The term refers to influenza disease caused by influenza viruses, but it is also widely and used incorrectly to refer to diseases that are similar run and caused by other viral respiratory pathogens. Influenza viruses are classified by their nucleotide and matrix proteins in the types A, B and C. Infection with the influenza C virus does not result in a typical influenza illness and is not discussed here. Influenza antigens haemagglutinin (H) is a glycoprotein on the surface of influenza virus, which allows the attachment of the virus to cellular Sialinsäurerezeptoren and fusion with the host cell membrane. Neuraminidase (NA) is another surface protein that degrades sialic acid enzymatically, whereby the release of the finished viruses is made possible by the infected host cell. There are 18 H types and 11 types NA, which means 198 possible combinations, but few are humae pathogens. EinAntigenrift refers to relatively small progressive mutations in pre-existing combinations of H and NA antigens, leading to the frequent emergence of new viral strains. These new strains can cause seasonal epidemics, because the protection is reduced by antibodies formed against the former base. An antigenic shift refers to the relatively rare development of new combinations of H and / or NA antigens, resulting from reassortment of subunits of the viral genome. Pandemics may result from antigen shifts because the antibodies against other strains (resulting from vaccination or natural infection) offer little or no protection against the new strain. Epidemiology Influenza causes in temperate climates year in autumn and winter a widespread sporadic disease (seasonal epidemics). Seasonal epidemics are caused by both the influenza A and influenza B virus and often occur in two waves-the first in school children and their household contacts (mostly younger people) and the second most in domesticated bound or institutionalized people, especially in the elderly. Influenza B viruses can cause minor diseases, but often cause at 3- to 5-year cycles epidemics with moderate to severe severity. Most influenza epidemics caused by a predominant serotype, but different influenza viruses can appear sequentially or simultaneously at a location where a virus can dominate in one place and another at a different location. Pandemics are much rarer. By 2013, there were six major pandemics, which were usually named after their alleged origin: 1889 Russian flu (H2N2) 1900: Old Hong Kong flu (H3N8) 1918: Spanish flu (H1N1) 1957: Asian flu (H2N2) 1968: Hong Kong flu (H3N2) 2009: swine flu (influenza A [H1N1] pdm09) influenza virus can be airborne by droplets by contact from person to person or through contact with contaminated objects transferred. The most important mechanism seems to be the airborne transmission. Risk Groups Certain patients have a high risk for complications from influenza: children <4 years adults> 65 years people with chronic diseases (such as cardiovascular diseases, diabetes mellitus, liver or kidney failure, hemoglobinopathies, immunodeficiency.) Females 2 . or third trimester of pregnancy patients with missing Schutzreflexcen or diseases denSekretverhalt promote (z. B. cognitive dysfunction, neuromuscular disease, stroke, seizure disorders). Patients taking ? 18 years aspirin (because this increases the risk of Reye’s syndrome) The increased in these patient groups morbidity and mortality may be due to an exacerbation of the underlying disease, acute respiratory distress syndrome, a primary influenza pneumonia or secondary bacterial pneumonias. Symptoms and signs The incubation period ranges from 1-4 days and is on average about 48 hours. In mild cases, many symptoms are similar to those of a flu infection (eg, sore throat, rhinorrhea.); a slight conjunctivitis may also occur. A typical influenza in adults is characterized by sudden onset with chills, fever, exhaustion, cough and generalized pain (especially in the back and legs). This leads to severe headaches, often with photophobia and retrobulbar pain. Respiratory symptoms may be easy to start yet, with “scratchy” sore throat, retrosternal burning, nonproductive cough, and occasionally cold. Later in the symptoms of a deep respiratory infection predominate; the cough may persist, be rough and productive. Gastrointestinal symptoms may occur, and seemed to be more common in the pandemic with the 2009 H1N1 strain. Children can have a sepsis-like syndrome intense nausea, vomiting or abdominal pain, infants. After 2-3 days the acute symptoms form back quickly, though the fever can last up to 5 days continue. Cough, weakness, sweating and fatigue may persist even weeks for several days, sometimes. Complications progressive cough, bloody sputum, dyspnea, and rales is suspected pneumonia. Persistent or recurrent fever and cough after the primary disease, indicate a secondary bacterial pneumonia. Encephalitis, myocarditis and myoglobinuria, sometimes with kidney failure often develop after influenza A or B infection. Reye syndrome (Reye’s syndrome) -charakterisiert by encephalopathy, fatty liver, increase in liver enzymes, increase of ammonia or both hypoglycemia and often lipemia-occurs during influenza B epidemics, especially in children after ingestion of aspirin. Diagnosis Clinical assessment Mainly for the purpose of surveillance or in pandemic phases: diagnostic Schnelltestverfahen pulse oximetry and chest X-ray in patients with severe respiratory symptoms, the diagnosis is usually made clinically in patients with a typical clinical picture when a frequent incidence of influenza in the region is known. Although there are many rapid tests available and most have a good specificity, but its sensitivity varies and they usually contribute little to improve patient care. Diagnostic tests should be carried out if the results influence clinical decision making. Reverse transcriptase PCR (RT-PCR) assays are sensitive and specific and can distinguish the different influenza types and subtypes. If this test is readily available, the results can lead to select an appropriate antiviral therapy. These tests are also useful to determine whether outbreaks of respiratory disease caused by influenza. A cell culture from nasopharyngeal swabs or aspirates takes several days and does not help to make decisions about the treatment of the patient. If patients lower respiratory symptoms (eg. As dyspnea, rales, which are found in lung study) should be done pulse oximetry and a chest x-ray to detect pneumonia. A primary influenza pneumonia manifests with focal or diffuse interstitial infiltrates or as acute respiratory distress syndrome (ARDS). A secondary bacterial pneumonia manifested rather than Lobär- or segment pneumonia. Prognosis Most patients recover completely again, although a full recovery can often take 1-2 weeks. However, influenza and influenza-like pneumonia are major causes of increased morbidity or mortality in patients at high risk. An antiviral therapy in these patients appears to reduce the incidence of lower respiratory illnesses and hospitalizations. An adequate antibacterial therapy reduced the mortality rate due to secondary bacterial pneumonia. Therapy Symptomatic therapy Sometimes antiviral drugs, the therapy takes place in most patients with symptomatic protection, hydration and antipyretic agents if necessary, acetylsalicylic acid is avoided in patients ? 18 years. Complicating bacterial infections require appropriate antibiotics. Medicine for influenza antiviral drugs that are given within 1-2 days after onset of symptoms, reducing the duration of fever, severity of symptoms, and time to return to normal activities. Treatment with antivirals is recommended for high-risk patients who develop influenza-like symptoms. This recommendation is based on data that suggest that early treatment can prevent complications in these patients. Among the drugs in influenza include the following: oseltamivir and zanamivir (neuraminidase inhibitors) amantadine and rimantadine (adamantanes) neuraminidase inhibitors interfere with the release of influenza viruses from infected cells and thus stop the spread of infection. Adamantanes block M2 ion channel, thereby affecting the viral “uncoating” inside the cell. They are only effective against influenza A virus (influenza B viruses lacking the M2 protein). The choice of the antiviral drug is determined by the resistance of the various influenza types and subtypes to the different drug difficult (see Table: drug resistance of the different influenza strains). When an RT-PCR test is readily available, the results can determine the treatment. When an RT-PCR is not available, patients can oseltamivir plus with zanamivir alone or with rimantadine. Are treated. Drug resistance of different strains of influenza virus amantadine or rimantadine, oseltamivir, zanamivir influenza A virus H3N2 Seasonal Resistant Sensitive Sensitive Seasonal H1N1 Susceptible Resistant Sensitive Pandemic H1N1 Resistant Sensitive Sensitive avian H5N1 Resistant Sensitive Sensitive influenza B viruses All Resistant Sensitive Sensitive Zanamivir is inhaled, two strokes (10 mg) two times a day, it can be used in adults and children ? 7 years. Zanamivir sometimes causes bronchospasm and should not be prescribed for patients with reactive airway disease, some Menschwen can not use an inhaler. Oseltamivir 75 mg p.o. is 2 times a day for patients> 12 years, prescribed; lower doses may be used in children from the age of 1 year. Oseltamivir can occasionally cause nausea and vomiting. In children, oseltamivir may reduce the incidence of otitis media, but there is no clear information as to whether the therapy of influenza prevents complications. Rimantadine is the preferred adamantane, because it has fewer side effects and is better tolerated. The treatment is stopped 1-2 days after symptoms have subsided or after 3-5 days. Rimantadine and amantadine can p.o. with a dosage of 100 mg be applied two times a day in adults ? 65; in adults> 65,100 mg can p.o. be applied 1 times daily. To avoid side effects due to an accumulation of the substances, doctors reduce the dose in children (2.5 mg / kg 2 times a day up to a maximum of 150 mg / day in children <10 years or 200 mg / day in children ? 10 years) reduced. In patients with impaired renal function the dose according to the "creatinine clearance" is adjusted. The Rimantadindosis should not exceed in patients with hepatic impairment 100 mg / day. In approximately 10% of patients who received amantadine, and approximately 2% of patients receiving rimantadine, there is a dose-dependent nervousness, insomnia or other CNS effects. These effects usually occur within 48 hours after initiation of therapy, are in the elderly and patients with diseases of the CNS or renal impairment pronounced and often form upon further application back. Furthermore, anorexia, nausea and constipation may occur. Prevention of influenza infections can be avoided by vaccination Annual Sometimes chemoprophylaxis (z. B. with antiviral drugs) Current commercial vaccines only protect against seasonal influenza. A vaccine for H5N1 avian influenza has been approved for persons> 18 years at high risk for H5N1 strain, but is only available to public health officials. Currently there are no vaccines for other bird flu viruses that are rarely associated with human disease (H7N7, H9N2, H7N3 and H7N9) are available. A prophylaxis is indicated in all patients, but especially important in high risk patients and medical staff. Vaccines The vaccines are modified annually based on recommendations of the WHO and the US Centers for Disease Control and Prevention (CDC) to detect the strains with the highest prevalence (usually two influenza A strains and one or two strains of influenza B) , Sometimes in the northern and southern hemispheres slightly different vaccines are used. If the vaccine the same HA and NA component contains as the circulating in the region of strain, the vaccine reduces the number of infections occur in healthy adults by 70-90%. In older people in community facilities, vaccination is less effective for the prevention of infections, but they reduce the rate occurring pneumonia and deaths by 60-80%. The vaccine-induced immunity is reduced by antigenic drift and is no longer present at a antigenic shift. There are two basic types of vaccines: multivalent inactivated Infuenza vaccine (MIV) attenuated influenza vaccine (LAIV) MIV is administered by intramuscular injection. Trivalent vaccines are gradually replaced by quadrivalent vaccine that cover an additional B virus strain. An egg protein-free vaccine (RIV3) is for patients who are between 18 and 49 years old and have any severity of egg allergy available. A high-dose trivalent vaccine is available for patients ? 65 years, but its effectiveness is still under investigation. Patients aged 6-35 months receive all MIV 0.25 ml and ? 3 years 0,5 ml. The adverse effects are usually only mild pain at the injection site that stop than a few days no longer. Fever, myalgia, and other systemic effects are uncommon. Multiple dose vials contain thimerosal, a mercury-based preservative. Public concern about a possible link between thimerosal and autism have been shown to be unfounded (anti-vaccination movement: thimerosal and autism); However, are single-dose vials that are thimerosal-free available. LAIV is administered intranasally in a dose of 0.25 ml in each vestibule. It can be used for healthy persons aged 2-49 years. This vaccine is not recommended for high-risk patients, pregnant women, household contacts of patients with severe immunodeficiency (z. B. with hematopoietic stem cell transplantation) or children with a long-term Acetylsalicylsäuretherapie. It should also not before 48 hours are administered after stopping drug treatment of influenza. Costs related to the vaccination related adverse effects are weak; Rhinorrhea is the most common and it can be a slight wheezing occur. LAIV should not suffer from children <5 years and reactive airway disease (eg. As known asthma, recurrent or shortly past Bronchoobstruktion), are given. Applies that children <8 years old and not vaccinated, received a primary dose and a booster dose at an interval of one month for both types of vaccines. A complete list of vaccines for the season 2013/2014 is available from the CDC (s. CDC Influenza Vaccines) .Impfempfehlungen an annual vaccination is recommended for all persons aged ? 6 months. The influenza vaccine is administered annually to maintain antibody titers as well as to enable the necessary to compensate for the antigenic drift modification of the vaccine. The vaccination should preferably take place in the fall, so be protective antibody titers during the winter influenza season in Germany (November to March). Vaccination (both MIV as LAIV also) should be avoided in people who have a severe egg allergy (if the only allergic manifestation urticaria is an egg-protein-free vaccine in patients aged 18 to 49 can be used or a have standard vaccine can be used if proper precautions are taken to counter a possible allergic reaction) Previously had a severe reaction to influenza vaccines developed within 6 weeks after a previous influenza vaccination Guillain-Barre syndrome (GBS) (it is not known whether influenza vaccination increases the risk of recurrent GBS in patients who previously had a GBS that was not with vaccination against influenza related) in the last 6 weeks had regardless of the cause, a GBS are <6 months old Antiviral drugs Although d ie vaccination is the preferred method of prevention, antiviral substances are also effective. Prophylactic antiviral drugs are indicated if influenza circulating among patients who were vaccinated only within the last two weeks, for which the vaccine is contraindicated, are immunocompromised and therefore do not respond to the vaccine. The administration of antiviral drugs does not affect the development of immunity of inactive vaccines. They can be stopped 2 weeks after the vaccination. If it can not be vaccinated, antiviral medications are given for the duration of the epidemic. If the circulating influenza types and subtypes are unknown, patients with either zanamivir alone (in patients for whom it is not contraindicated) or with a combination of oseltamivir and rimantadine can be treated. Key points Smaller antigen drift in H and / or NA antigens produce strains that cause seasonal epidemics; rare antigen shifts, which lead to new combinations of H and NA antigens can cause a pandemic with significant mortality. Influenza itself can cause pneumonia; Patients with influenza can develop a secondary bacterial pneumonia. The diagnosis is made clinically usually, but sensitive and specific RT-PCR assays can distinguish types and subtypes of influenza from one another and thus in the selection of antiviral therapy and determining whether outbreaks of respiratory disease caused by influenza, help. The treatment of most patients is symptomatic. Antiviral drugs that are administered at an early stage can easily nonuniformity reducer, the duration and severity of symptoms, but they are generally used only in high-risk patients; different types and subtypes of influenza are resistant to different drugs. All persons aged ? 6 months be vaccinated annually; antiviral drugs can be used for prevention in immunocompromised patients (who may not respond to the vaccine) and used in patients with contraindications to vaccination.

Health Life Media Team

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