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Jai Ganesh

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Influenza

Influenza

Gist

Influenza, or the flu, is a contagious respiratory illness caused by influenza viruses, with common symptoms including fever, cough, sore throat, muscle aches, and fatigue. While many people recover on their own, it can lead to severe complications. The best prevention is an annual flu vaccine, but other measures include frequent hand washing and avoiding close contact with sick individuals. 

The flu typically lasts for a week or two, but symptoms can vary in duration. While most acute symptoms like fever and body aches usually improve within 3 to 7 days, a cough and fatigue can linger for two weeks or longer. It's important to monitor your symptoms, as some people, especially those in high-risk groups, may develop complications or require medical attention. 

Is influenza contagious?

Yes, influenza is a contagious respiratory illness that spreads easily from person to person through respiratory droplets from coughs and sneezes. It is highly contagious, and a person can spread the virus from about one day before feeling sick until about five to seven days after symptoms begin. Staying home when sick and practicing good hygiene are key to preventing its spread.

Summary:

Overview

Comparison of COVID-19, cold and flu symptoms. Shared symptoms can include sore throat, cough, fever, body aches and more.

The flu, common cold and COVID-19 have similar symptoms. The flu and COVID-19 can be severe, but colds rarely are.

What is the flu (influenza)?

The flu is an illness you get from the influenza virus. It causes symptoms like head and body aches, sore throat, fever and respiratory symptoms, which can be severe. Flu is most common in winter months, when many people can get sick at once (an epidemic).

When is flu season?

Flu season — when cases of the flu go up dramatically — in the Northern Hemisphere (which includes the U.S.) is October through May. The highest number of cases (peak) usually happen between December and February.

How common is the flu?

The flu is one of the most common infectious diseases. Every flu season, about 20 to 40 million people in the U.S. catch the flu.

What is the difference between the flu and the common cold?

The flu and the common cold can have similar symptoms, like runny nose and cough. But cold symptoms are usually mild and flu symptoms can be severe and lead to serious complications.

Different viruses cause colds and the flu.

How do I know if I have the flu or COVID-19?

Since they have similar symptoms, the only way to know for sure if you have the flu or COVID-19 is to get tested. They both have a risk of serious illness. But different viruses cause these infections, and providers treat them with different medications.

Who is at higher risk for complications from the flu?

Certain health conditions can put you at higher risk for severe illness from the flu. This includes life-threatening complications that require hospitalization. You’re at higher risk for serious illness if you:

* Have asthma, COPD or another chronic lung disease.
* Have a history of kidney, liver, neurological, heart or blood vessels disease, including stroke.
* Have a condition that causes issues with muscle function or makes it difficult to cough, swallow or clear fluids from your airways.
* Have diabetes.
* Have a weakened immune system (from HIV/AIDS, cancer or immunosuppressive medications).
* Have a blood disorder, like sickle cell disease.
* Have a BMI greater than 30 (have obesity).
* Are under 5 years old or over 65 years old.
* Are pregnant.
* Are under 19 years old and take aspirin regularly.
* Live in a long-term care facility.
* Non-Hispanic Black people, non-Hispanic American Indians, Alaska Native people and Hispanic or Latino people have the highest rates of severe illness from the flu compared to non-Hispanic White people and non-Hispanic Asian people.

Symptoms and Causes

With so many symptoms in common, it can be hard to tell the difference between a cold and the flu. Here’s how to tell which is which.

* What are the symptoms of the flu?

Symptoms of the flu usually come on quickly, and can include:

* Fever.
* Chills.
* Body aches.
* Cough.
* Headache.
* Sore throat.
* Runny or stuffy nose (congestion).
* Tiredness or feeling run down.
* Diarrhea or vomiting (usually only in kids).

You may not have all of these symptoms.

What causes the flu?

The influenza virus causes flu. Influenza A, B and C are the most common types that infect people. Influenza A and B are seasonal (most people get them in the winter) and have more severe symptoms. Influenza C doesn’t cause severe symptoms and it’s not seasonal — the number of cases stays about the same throughout the year.

H1N1 (“swine flu”) and bird flu are both subtypes of influenza A.

Details

Influenza, commonly known as the flu, is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms begin one to four (typically two) days after exposure to the virus and last for about two to eight days. Diarrhea and vomiting can occur, particularly in children. Influenza may progress to pneumonia from the virus or a subsequent bacterial infection. Other complications include acute respiratory distress syndrome, meningitis, encephalitis, and worsening of pre-existing health problems such as asthma and cardiovascular disease.

There are four types of influenza virus: types A, B, C, and D. Aquatic birds are the primary source of influenza A virus (IAV), which is also widespread in various mammals, including humans and pigs. Influenza B virus (IBV) and influenza C virus (ICV) primarily infect humans, and influenza D virus (IDV) is found in cattle and pigs. Influenza A virus and influenza B virus circulate in humans and cause seasonal epidemics, and influenza C virus causes a mild infection, primarily in children. Influenza D virus can infect humans but is not known to cause illness. In humans, influenza viruses are primarily transmitted through respiratory droplets from coughing and sneezing. Transmission through aerosols and surfaces contaminated by the virus also occur.

Frequent hand washing and covering one's mouth and nose when coughing and sneezing reduce transmission, as does wearing a mask. Annual vaccination can help to provide protection against influenza. Influenza viruses, particularly influenza A virus, evolve quickly, so flu vaccines are updated regularly to match which influenza strains are in circulation. Vaccines provide protection against influenza A virus subtypes H1N1 and H3N2 and one or two influenza B virus subtypes. Influenza infection is diagnosed with laboratory methods such as antibody or antigen tests and a polymerase chain reaction (PCR) to identify viral nucleic acid. The disease can be treated with supportive measures and, in severe cases, with antiviral drugs such as oseltamivir. In healthy individuals, influenza is typically self-limiting and rarely fatal, but it can be deadly in high-risk groups.

In a typical year, five to 15 percent of the population contracts influenza. There are 3 to 5 million severe cases annually, with up to 650,000 respiratory-related deaths globally each year. Deaths most commonly occur in high-risk groups, including young children, the elderly, and people with chronic health conditions. In temperate regions, the number of influenza cases peaks during winter, whereas in the tropics, influenza can occur year-round. Since the late 1800s, pandemic outbreaks of novel influenza strains have occurred every 10 to 50 years. Five flu pandemics have occurred since 1900: the Spanish flu from 1918 to 1920, which was the most severe; the Asian flu in 1957; the Hong Kong flu in 1968; the Russian flu in 1977; and the swine flu pandemic in 2009.

Signs and symptoms

Symptoms of influenza, with fever and cough the most common symptoms.

The symptoms of influenza are similar to those of a cold, although usually more severe and less likely to include a runny nose. The time between exposure to the virus and development of symptoms (the incubation period) is one to four days, most commonly one to two days. Many infections are asymptomatic. The onset of symptoms is sudden, and initial symptoms are predominately non-specific, including fever, chills, headaches, muscle pain, malaise, loss of appetite, lack of energy, and confusion. These are usually accompanied by respiratory symptoms such as a dry cough, sore or dry throat, hoarse voice, and a stuffy or runny nose. Coughing is the most common symptom. Gastrointestinal symptoms may also occur, including nausea, vomiting, diarrhea, and gastroenteritis, especially in children. The standard influenza symptoms typically last for two to eight days. Some studies suggest influenza can cause long-lasting symptoms in a similar way to long COVID.

Symptomatic infections are usually mild and limited to the upper respiratory tract, but progression to pneumonia is relatively common. Pneumonia may be caused by the primary viral infection or a secondary bacterial infection. Primary pneumonia is characterized by rapid progression of fever, cough, labored breathing, and low oxygen levels that cause bluish skin. It is especially common among those who have an underlying cardiovascular disease such as rheumatic heart disease. Secondary pneumonia typically has a period of improvement in symptoms for one to three weeks[ followed by recurrent fever, sputum production, and fluid buildup in the lungs, but can also occur just a few days after influenza symptoms appear. About a third of primary pneumonia cases are followed by secondary pneumonia, which is most frequently caused by the bacteria Streptococcus pneumoniae and Staphylococcus aureus.

Additional Information

Influenza, or the flu, is a contagious respiratory illness caused by influenza viruses, with common symptoms including fever, cough, sore throat, muscle aches, and fatigue. While many people recover on their own, it can lead to severe complications. The best prevention is an annual flu vaccine, but other measures include frequent hand washing and avoiding close contact with sick individuals. 

Symptoms

* Sudden onset of fever
* Dry cough
* Sore throat
* Runny nose
* Headache
* Muscle and joint pain
* Severe malaise (feeling unwell)
* Fatigue

Prevention

Vaccination: Get a flu shot every year, as it is the most effective way to prevent the flu and its complications.
Hygiene: Wash your hands frequently with soap and water or use an alcohol-based hand sanitizer.
Avoid contact: Stay away from sick people and avoid touching your face.

Treatment

Rest: Get plenty of rest and stay warm to allow your body to fight the virus.
Hydration: Drink plenty of liquids like water, juice, and warm soups.
Pain relievers: Over-the-counter pain relievers can help manage fever, headaches, and body aches, but children and teenagers should not be given aspirin due to the risk of Reye's syndrome.
Medical attention: Seek medical attention, especially if you are in a high-risk group, or if you develop severe symptoms like difficulty breathing or chest pain. In some cases, a doctor may prescribe antiviral drugs.

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