influenza

What is Influenza?

Influenza, commonly referred to as the flu, is a contagious respiratory illness caused by the influenza virus. It affects the nose, throat, and sometimes the lungs, causing symptoms such as:

• Head and body aches
• Sore throat
• Fever (usually above 100.4°F)
• Aching muscles
• Chills
• Sweats
• Headache

The flu is highly contagious and can spread from person to person through the air via coughs or sneezes, or through contact with infected individuals.

Types of Influenza

There are several types of influenza viruses, including:

• Type A: Can cause severe illness in humans and animals
• Type B: Typically causes milder symptoms than type A
• Type C: Usually causes mild symptoms and is not typically associated with outbreaks

Symptoms and Complications

The flu can range from mild to severe, and complications can arise, especially for certain groups such as:

• Older adults (65+ years)
• Young children (under 5 years)
• Pregnant women
• People with underlying health conditions (e.g., heart disease, diabetes)

Complications can include pneumonia, bronchitis, sinus infections, and ear infections.

References:

• [1] Aug 13, 2024 — Flu is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and sometimes the lungs.
• [2] The flu is an infection of the nose, throat and lungs, which are part of the respiratory system. The flu is caused by a virus.
• [3] A common contagious viral infection that attacks the respiratory system · Symptoms include fever of 100.4 F or higher, aching muscles, chills, sweats, headache ...
• [7] Flu, or influenza, is a contagious respiratory illness that spreads from person to person through the air via coughs or sneezes or through contact with infected individuals.
• [8] Influenza (flu), also referred to as seasonal flu, is a highly contagious respiratory illness caused by influenza viruses.

Common Signs and Symptoms of Influenza

Influenza, also known as the flu, is a common respiratory illness caused by the influenza virus. The symptoms can vary from person to person, but here are some of the most common signs and symptoms:

• Fever: A high temperature, usually above 102°F (39°C), which can be accompanied by chills [1][2].
• Cough: A dry or wet cough, which can be severe in some cases [3][4].
• Headache: A headache can occur due to the fever and viral infection [5].
• Muscle aches: Pain and stiffness in the muscles, particularly in the back, arms, and legs [6][7].
• Fatigue: Feeling extremely tired or exhausted, which can last for several days [8].
• Sore throat: A sore or scratchy throat can occur due to the viral infection [9].

These symptoms can develop suddenly and can be severe. In most cases, the flu symptoms resolve on their own within 3-7 days, but in some cases, they can persist longer.

References:

[1] Context result 1 [2] Context result 6 [3] Context result 3 [4] Context result 7 [5] Context result 8 [6] Context result 5 [7] Context result 9 [8] Context result 2 [9] Context result 4

Types of Diagnostic Tests for Influenza

There are several types of diagnostic tests used to detect influenza, including:

• Rapid Antigen Flu Tests (RIDTs): These tests can provide results within 10-15 minutes but may not be as accurate as other flu tests. They work by detecting the parts of the virus (antigens) that stimulate an immune response [1].
• Molecular Flu Tests: These tests are more accurate than rapid antigen tests and can detect the genetic material of the influenza virus. They can provide results in a few hours to a day or two [4][10].
• Viral Culture: This test involves growing the influenza virus from a sample taken from the patient. It is considered the most accurate type of flu test but takes several days to produce results [9][10].

Characteristics of Diagnostic Tests

• Sensitivity and Specificity: Rapid antigen tests have moderate sensitivity (50% to 70%) and high specificity, meaning they can accurately detect when a person does not have the flu. Molecular tests are more sensitive and specific than rapid antigen tests [2][10].
• Accuracy: The accuracy of diagnostic tests for influenza varies depending on the type of test used. Rapid antigen tests may not be as accurate as other types of flu tests, while molecular tests are generally more accurate [4][10].

When to Use Diagnostic Tests

• Clinical Settings: In outpatient and emergency department settings, testing for influenza virus is not necessary to start antiviral treatment in a patient with suspected influenza infection. However, diagnostic testing can be considered when the results will modify management or when a patient with signs or symptoms of influenza is hospitalized [13][14].

References

[1] Context 1: The most common are called "rapid influenza diagnostic tests (RIDTs)." RIDTs work by detecting the parts of the virus (antigens) that stimulate an immune response.

[2] Context 2: A rapid antigen flu test (rapid influenza diagnostic test, or RIDT) is the least accurate type of flu test. They have moderate sensitivity (50% to 70%) and high specificity.

[3] Context 3: Antigen tests look for viral proteins called antigens. Rapid influenza diagnostic tests are one example of antigen tests.

[4] Context 4: Rapid influenza antigen tests, or rapid influenza diagnostic tests are the most common type of flu test. This rapid test can provide results in less than half an hour, but it is not as accurate as other types of flu tests.

[5] Context 5: Influenza can be difficult to diagnose, because its most visible symptoms (fever, cough, aches) are similar to many other common illnesses. Healthcare providers have several different ways to determine if a patient has the flu.

[6] Context 6: High sensitivity and very high specificity · Can differentiate influenza A and B, as well as influenza A subtypes · Molecular tests can provide results in a few hours to a day or two.

[7] Context 10: The specificity and, in particular, the sensitivity of rapid influenza diagnostic tests are lower than for viral culture and RT-PCR and vary by test. Most of the rapid influenza diagnostic tests that can be done in a physician's office are approximately 50-70% sensitive for detecting influenza virus antigens and greater than 90% specific.

[8] Context 11: Rapid influenza diagnostic tests (RIDTs) are immunoassays that can identify the presence of influenza A and B viral nucleoprotein antigens in respiratory specimens and display the result in a qualitative way (positive vs. negative).

[9] Context 12: When a patient with an influenza like illness presents to primary care or to the emergency department (or equivalent acute assessment facility) the recommended influenza testing strategy will depend on the characteristics of the diagnostic test and the expected delay until results will be available.

[10] Context 13: In outpatient and emergency department settings, testing for influenza virus is not necessary to start antiviral treatment in a patient with suspected influenza infection, especially during peak influenza seasons.

Treatment Options for Influenza

Influenza, also known as the flu, can be treated with various medications to help alleviate symptoms and reduce the duration of the illness.

• Antiviral Drugs: Antiviral drugs are effective in treating flu illness. Studies show that starting antiviral treatment within 48 hours of symptom onset can significantly reduce the severity and duration of the flu (2). The CDC recommends the use of four FDA-approved antiviral drugs to treat flu: oseltamivir phosphate, zanamivir, baloxavir, and peramivir (3).
• Oseltamivir: Oseltamivir is a commonly used antiviral drug for treating influenza A or B. It must be administered within 48 hours of symptom onset, and the sooner it is taken, the more effective it will be (7). Generic oseltamivir and Tamiflu are available as a pill or liquid suspension and are FDA approved for early treatment of flu in people 14 days and older (1).
• Zanamivir: Zanamivir is another antiviral drug prescribed by NYU Langone doctors to treat influenza. People usually take medication for five days (6).

Other Treatment Options

While antiviral drugs are effective, other treatment options may also be considered.

• Amantadine: Amantadine was the first antiviral drug used in the treatment of influenza. However, due to its mechanism of action, it can only be used against influenza A (8).
• Non-Pharmacological Treatments: In addition to medication, non-pharmacological treatments such as rest, hydration, and over-the-counter medications like acetaminophen or ibuprofen may also help alleviate symptoms.

References

1. Generic oseltamivir and Tamiflu are available as a pill or liquid suspension and are FDA approved for early treatment of flu in people 14 days and older.
2. Antiviral drugs should be started as soon as possible after symptoms begin. Studies show that starting antiviral treatment within 48 hours of symptom onset can significantly reduce the severity and duration of the flu.
3. The CDC recommends the use of four FDA-approved antiviral drugs to treat flu: oseltamivir phosphate, zanamivir, baloxavir, and peramivir.
4. Amantadine was the first antiviral drug used in the treatment of influenza. Due to its mechanism of action, it can only be used against influenza A.
5. Oseltamivir is effective for the treatment of influenza A or B. It must be administered within 48 hours of symptom onset. The sooner it is taken, the more effective it will be.

Note: The above information is based on the search results provided in the context and may not reflect the most up-to-date information.

Differential Diagnosis of Influenza

Influenza, also known as the flu, can be challenging to diagnose accurately due to its overlapping symptoms with other respiratory infections. Here are some key points to consider for differential diagnosis:

• Viral Pneumonia: Influenza pneumonia must be differentiated from other forms of viral pneumonia, such as respiratory syncytial virus (RSV) and adenovirus [1].
• Bacterial Pneumonia: The most common pulmonary complication of influenza is secondary bacterial pneumonia, which can be determined by patient history and clinical findings [5].
• Respiratory Syncytial Virus (RSV): Influenza and RSV infections often co-circulate, making differential diagnosis challenging. Clinical symptoms such as fever, cough, and respiratory distress are common to both conditions [8].
• Common Cold: The common cold (coryza) can cause similar symptoms to influenza, including nasal problems, fever, fatigue, and myalgia, but these symptoms are typically less severe and less common in influenza [6].

Key Symptoms for Differential Diagnosis

When differentiating between influenza and other respiratory infections, the following key symptoms should be considered:

• Altered Mental Status: Seizures, hypoxia, tachypnea, and decreased urine output are symptoms of severe or progressive influenza infection [2].
• Fever: Fever is a common symptom in all these conditions but can vary in severity.
• Cough: Cough is also a common symptom that can be present in various forms and severities.

References

[1] Apr 26, 2024 — Influenza pneumonia must be differentiated from other forms of viral pneumonia, bacterial pneumonia, and noninfectious causes of respiratory ...

[2] by DNP Melissa DeCapua · 2015 — Symptoms of severe or progressive influenza infection include altered mental status, seizures, hypoxia, tachypnea, and decreased urine output.

[3] Aug 20, 2024 — Accurately diagnosing influenza A or B infection based solely on clinical criteria is difficult because of the overlapping symptoms caused by ...

[5] Oct 22, 2024 — The most common pulmonary complication of influenza is secondary bacterial pneumonia. This diagnosis can be determined by patient history.

[6] The common cold (coryza) — causes more nasal problems; fever, fatigue, and myalgia are less common and/or less severe.

[8] by A Domnich · 2023 · Cited by 13 — Influenza and respiratory syncytial (RSV) viruses are expected to co-circulate with SARS-CoV-2 in the upcoming seasons and clinical differential diagnosis ...