Flu (Influenza): Symptoms, Causes, Treatment

What are the symptoms of the flu?

The flu, or influenza, is a contagious respiratory illness caused by influenza viruses. Symptoms of the flu can vary in severity and may include:

1. Fever: Often high, typically above 100.4°F (38°C), and can last for several days.
2. Chills: Accompanying fever, sometimes severe.
3. Cough: Dry or productive cough, which can be persistent and worsen over time.
4. Sore throat: Pain or irritation in the throat, especially when swallowing.
5. Runny or stuffy nose: Nasal congestion or discharge is common.
6. Muscle or body aches: Generalized body aches and pains, often severe.
7. Fatigue: Profound tiredness and weakness, which can last for several weeks.
8. Headache: Often severe and may be accompanied by sinus pressure.
9. Weakness: Feeling physically weak and exhausted.
10. Loss of appetite: Decreased desire to eat due to symptoms of illness.
11. Nausea or vomiting: More common in children than adults, but can occur in both.
12. Diarrhea: May occur, especially in children.

It’s important to note that symptoms of the flu can overlap with those of other respiratory illnesses, such as the common cold or COVID-19. If you experience symptoms of the flu, especially during flu season, it’s a good idea to consult with a healthcare provider for an accurate diagnosis and appropriate treatment. Additionally, getting a flu shot each year can help reduce the risk of contracting the flu and lessen the severity of symptoms if you do get sick.

What are the causes of the flu?

The flu, or influenza, is caused by influenza viruses. There are four types of influenza viruses: A, B, C, and D. Influenza A and B viruses are responsible for most cases of the flu in humans.

These viruses are highly contagious and spread from person to person through respiratory droplets produced when an infected person talks, coughs, or sneezes. The flu can also spread by touching a surface or object that has the flu virus on it and then touching the mouth, nose, or possibly the eyes.

Influenza viruses can undergo changes, known as antigenic drift and antigenic shift, which can lead to new strains of the virus. These changes are why the flu vaccine needs to be updated regularly to protect against the most prevalent strains of the virus each flu season.

How is the diagnosis of the influenza made?

The diagnosis of influenza is usually based on a combination of symptoms, physical examination, and sometimes laboratory tests. Here’s how it’s typically done:

1. Symptoms: The symptoms of influenza, such as fever, cough, sore throat, body aches, and fatigue, are often distinct from those of other respiratory illnesses. The presence of these symptoms during flu season increases the likelihood of influenza.
2. Physical examination: A healthcare provider may perform a physical examination to look for signs of influenza, such as redness of the eyes, throat, or nasal passages, as well as listen to the lungs for signs of pneumonia.
3. Rapid influenza diagnostic tests (RIDTs): These tests can detect influenza viral antigens in respiratory tract specimens (e.g., nasal swab). They provide quick results (usually within 15-30 minutes) but are not as sensitive as other tests and may produce false-negative results.
4. Molecular tests (RT-PCR): Reverse transcription-polymerase chain reaction (RT-PCR) tests are highly sensitive and specific for detecting influenza viruses. They are often used when a more accurate diagnosis is needed, such as in severe cases or when the results will impact patient care.
5. Viral culture: In some cases, a viral culture may be performed to isolate and identify the influenza virus. This test is more time-consuming and is less commonly used than molecular tests.

It’s important to note that the flu is often diagnosed based on symptoms and clinical judgment, especially during flu season when the virus is circulating widely. Treatment is usually based on symptoms and the likelihood of influenza, rather than waiting for test results, which may not be immediately available.

What is the treatment for the flu?

The treatment for the flu (influenza) focuses on relieving symptoms and reducing the severity of the illness. It typically includes:

1. Antiviral medications: Prescription antiviral drugs, such as oseltamivir (Tamiflu), zanamivir (Relenza), peramivir (Rapivab), or baloxavir marboxil (Xofluza), may be prescribed to shorten the duration of the flu and reduce the severity of symptoms. These medications are most effective when taken within 48 hours of the onset of symptoms.
2. Over-the-counter medications: These can help relieve symptoms such as fever, aches, and congestion. Common options include acetaminophen (Tylenol) or ibuprofen (Advil, Motrin) for fever and body aches, as well as decongestants and cough suppressants.
3. Fluids: Drinking plenty of fluids, such as water, herbal tea, or clear broth, helps prevent dehydration and loosens mucus in the lungs.
4. Rest: Getting plenty of rest allows the body to focus its energy on fighting the virus.
5. Humidifier: Using a humidifier or taking a steamy shower can help ease congestion and cough.
6. Isolation: To prevent the spread of the flu, it’s important to stay home from work or school until at least 24 hours after your fever is gone without the use of fever-reducing medications.

In some cases, especially for people at high risk of flu-related complications, such as older adults, young children, pregnant women, and those with certain medical conditions, antiviral medications may be recommended even if started more than 48 hours after the onset of symptoms. It’s important to consult with a healthcare provider for personalized recommendations.