Influenza is a viral respiratory infection caused by orthomyxovirus resulting in fever, coryza, cough, headache, and malaise - three strains exists A, B and C
- Patients will present with fever, headache, myalgia and malaise
- Complications from influenza are most common in the very young, very old, and those with preexisting comorbidities
- Everyone aged ≥ 6 mo should receive annual influenza vaccination
- Antiviral treatment reduces the duration of illness by about 1 day and should be specifically considered for high-risk patients -
- Oseltamivir (Tamiflu) and zanamivir (Relenza) (neuraminidase inhibitors) Treat A + B
Diagnosis is usually clinical, rapid antigen test can be performed in clinic
- Rapid serology test are often available and are most accurate during the first few days of illness
- The virus can be isolated from the throat or nasal mucosa - viral cultures take 3-7 days to return
- CXR in primary influenza pneumonia will show bilateral diffuse infiltrates
Can treat with medications if symptoms are less than 48 hours in duration
- Zanamivir and Oseltamivir both treat influenza A and B (think Dr. “OZ” treats the flu)
- Oseltamivir (Tamiflu) 75 mg PO two times per day for 5 days
- Amantadine and Rimantadine treat only influenza A
- The use of salicylates should be avoided, particularly in children below 18 years of age, because of association with Reye's syndrome. Remember Bismuth contains salicylates, should be avoided and could be a cause of Reye's syndrome.
Responsible use of antivirals:
Antiviral treatment depends on current resistance patterns each year; check www.cdc.gov/flu or local health department for current patterns. Antivirals are most effective if administered within 1st 48 hours in those with laboratory-confirmed (or highly suspected based on clinical findings) influenza illness.
Antivirals within 48 hours of symptom onset recommended if at risk of complications (ie. Diabetes, CHD, COPD, Asthma, etc.)
Antivirals recommended if hospitalized
Antivirals may be considered for persons not at increased risk of complications from influenza whose onset of symptoms is within the past 48 hours and who wish to shorten the duration of illness and further reduce their relatively low risk of complications.
Symptomatic treatment is preferred for those patients without risk factors and without signs of lower respiratory tract infection
|Influenza, commonly called the flu, is an infectious disease caused by an RNA virus of the Orthomyxovirus family. This is an enveloped virus with single-stranded negative sense linear genome. The genome is also segmented into 8 segments and has helical protein capsid. Virulence mechanisms include hemagglutinin, which is an antigenic glycoprotein found on the surface of influenza viruses that aids in viral entry of a cell and neuraminidase, an enzyme that plays an important role in the release of virion progeny from infected cells. This virus has the capacity to undergo reassortment of the genome to cause major changes in the strain of influenza. This major change is commonly referred to as genetic shift and can be highly dangerous because the human immune system has difficulty recognizing the new strain of virus. In contrast, genetic drift refers to minor antigenic mutations that occur and are associated with gradual loss of immunity. Common symptoms of influenza virus include chills, fever, sore throat, muscle pains, headache, and fatigue. Complications include Reye’s syndrome, a potentially fatal disease commonly associated with salicylate use in children with influenza, and the virus can also be a trigger for Guillan-Barre.|
|Zanamivir (Relenza) and Oseltamivir (Tamiflu) are antiviral medications used to treat and provide prophylaxis against influenza A and B. These drugs work by binding to neuraminidase, preventing the virus from escaping its host cell and infecting others.|
|Reye’s syndrome is a disorder associated with salicylate use in children with viral illnesses, such as the chickenpox and influenza. For this reason, aspirin and other NSAIDs should be avoided in this population. Instead, acetaminophen can be used. This syndrome is known to affect various organs throughout the body including fatty changes in the liver. As the child’s liver begins to fail, lab results may show increased liver enzymes, such as AST, ALT, and increased ammonia levels. Reye’s syndrome is characterized by acute encephalopathy. Children should be monitored closely for signs of increasing ICP, such as a change in level of consciousness, headache, vomiting, abnormal/asymmetrical pupils, posturing, and/or seizures. Early detection and treatment of Reye’s syndrome is essential, as death may result within hours if left untreated.|
Ciprofloxacin is indicated for postexposure prophylaxis of anthrax.
Clarithromycin is indicated for prophylaxis against disseminated Mycobacterium avium complex.
Alpha-2b interferon (Avonex)
Alpha-2b interferon is indicated for treatment of several disorders, such as chronic hepatitis B & C, but has no role in prophylactic treatment of any condition.
See D for explanation.
See D for explanation.
See D for explanation.
Amantadine is only used to treat influenza A.
Acyclovir is used to treat viral infections due to certain herpes viruses.
Nevirapine is used to treat infection due to HIV.