The Flu: Everything You Must Know for the 2020-2021 Season
10 rows†Ј Flu is different from a cold. Flu usually comes on suddenly. People who have flu often feel. Aug 31, †Ј Flu signs and symptoms usually come on suddenly. People who are sick with flu often feel some or all of these symptoms: Fever* or feeling feverish/chills; Cough; Sore throat; Runny or stuffy nose; Muscle or body aches; Headaches; Fatigue (tiredness) Some people may have vomiting and diarrhea, though this is more common in children than adults.
Influenzacommonly called " 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 typically begin 1Ч4 days after exposure to the virus and last for about 2Ч8 days. What can i do for weight loss and vomiting can occur, particularly in children.
Influenza may progress to pneumoniawhich can be caused by the primary viral infection or by a secondary bacterial infection. Other complications of infection include acute respiratory distress syndromemeningitisencephalitisand worsening of pre-existing health problems such as asthma and cardiovascular disease.
There are four types of influenza virus, termed influenza viruses A, B, C, and D. Aquatic birds are the primary reservoir of Influenza A virus IAVwhat are the symptoms of flu virus is also widespread in various mammals, including humans and pigs. How to catch lugia on pokemon pearl can infect humans but is not known to cause illness.
In humans, influenza viruses are primarily transmitted through respiratory droplets produced from coughing and sneezing. Transmission through aerosols and intermediate objects and surfaces contaminated by the virus also occur.
Frequent hand washing and covering one's mouth and nose when coughing and sneezing reduce transmission. Annual vaccination can help to provide protection against influenza. Influenza viruses, particularly IAV, evolve quickly, so flu vaccines are updated regularly to match which influenza strains are in circulation.
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. There are 3Ч5 million severe cases what are the symptoms of flu virus, with up todeaths 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 of the world, the number how to write a social studies report influenza cases peaks during winter, whereas in the tropics influenza can occur year-round. Since the late s, large outbreaks of novel influenza strains that spread globally, called pandemics, have occurred every 10Ч50 years.
Five flu pandemics have occurred since the Spanish flu in Ч, which was the most severe flu pandemic, the Asian flu inthe Hong Kong flu inthe What is lte vs 4g flu inand the swine flu pandemic. The time between exposure to the virus and development of symptoms, called the incubation periodis 1Ч4 days, most commonly 1Ч2 days. Many infections, however, are asymptomatic. These symptoms 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. The standard influenza symptoms typically last for 2Ч8 days. 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 by 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 how to put your name on share a coke disease.
Secondary pneumonia typically has a period of improvement in symptoms for 1Ч3 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.
Influenza viruses comprise four species. Each of the four species is the sole member of its own genus, and the four influenza genera comprise four of the seven genera in the family Orthomyxoviridae.
They are:  . IAV is responsible for most cases of severe illness as well as seasonal epidemics and occasional pandemics. It infects people of all ages what are the symptoms of flu virus tends to disproportionately cause severe illness in the elderly, the very young, and those who have chronic health issues.
Birds are the primary reservoir of IAV, especially aquatic birds such as ducks, geese, shorebirds, and gulls,   but the virus also circulates among mammals, including pigs, horses, and marine mammals. IAV is classified into subtypes based on the viral proteins haemagglutinin H and neuraminidase N. Most potential combinations have been reported in birds, but H and N have only been found in bats.
IBV mainly infects humans but has been identified in seals, horses, dogs, and pigs. ICV, like IBV, what are the symptoms of flu virus primarily found in humans, though it also has been detected in pigs, feral dogs, dromedary camels, cattle, and dogs.
IDV has been isolated from pigs and cattle, the latter being the natural reservoir. Infection has also been observed in humans, horses, dromedary camels, and small ruminants such as goats and sheep. While cattle workers have occasionally tested positive to prior IDV infection, it is not known to cause disease in humans.
Because of this antigenic stability, relatively few novel lineages emerge. Influenza viruses have a negative-sensesingle-stranded RNA genome that is segmented. The final genome segment encodes the viral nucleoprotein NP. The virus particle, called a virion, is spherical, filamentous, or pleomorphic in shape and 80Ч nanometers nm in diameter.
The envelope is reinforced structurally by matrix proteins on the interior that enclose the RNPs,  and the envelope contains HA and NA or HEF  proteins extending outward from the exterior surface of the envelope. HA and HEF  proteins have a distinct "head" and "stalk" structure. M2 proteins form proton ion channels through the viral envelope that are required for viral entry and exit. IBVs contain a surface protein named NB that is anchored in the envelope, but its function is unknown.
The viral life cycle begins by binding to a target cell. Binding is mediated by the viral HA proteins on the surface of the evelope, which bind to cells that contain sialic acid receptors on the surface of the cell membrane. Prior to binding, NA proteins promote access to target cells by degrading mucous, which helps to remove extracellular decoy receptors that would impede access to target cells.
The endosome is acidified by cellular vATPase  to have lower pH, which triggers a conformational change in HA that allows fusion of the viral envelope with the endosomal membrane. RNPs are then imported into the nucleus with the help of viral localization signals.
Newly synthesized viral polymerase subunits and NP proteins are imported to the nucleus to further increase the rate of viral replication and form RNPs.
Progenic viruses leave the cell by budding from the cell membrane, which is initiated by the accumulation of M1 proteins at the cytoplasmic side of the membrane. The viral genome is incorporated inside a viral envelope derived from portions of the cell membrane that have HA, NA, and M2 proteins.
At the end of budding, HA proteins remain attached to cellular sialic acid until they are cleaved by the sialidase activity of NA proteins.
The virion is then released from the cell. The sialidase activity of NA also cleaves any sialic acid residues from the viral surface, which helps prevent newly how to create a home office in your living room viruses from aggregating near what pre med major is the best cell surface and improving infectivity.
Two key processes that influenza viruses evolve through are antigenic drift and antigenic shift. Antigenic drift is when an influenza virus's antigens change due to the gradual accumulation of mutations in the antigen's HA or NA gene.
Antigenic drift is especially common for the HA protein, what are the symptoms of flu virus which just a few amino acid changes in the head region can constitute antigenic drift.
HA is the main component of inactivated vaccines, so surveillance monitors antigenic drift of this antigen among circulating strains.
Antigenic evolution of influenza viruses of humans appears to be faster than influenza viruses in swine and equines. In wild birds, within-subtype antigenic variation appears to be limited but has been observed in poultry. Antigenic shift is a sudden, drastic change in an influenza virus's antigen, usually HA.
During antigenic shift, antigenically different strains that infect the same cell can reassort genome segments what are the symptoms of flu virus each other, producing hybrid progeny. Since all influenza viruses have segmented genomes, all are capable of reassortment. In particular, reassortment is very common in AIVs, creating a large diversity of influenza viruses in birds, but is uncommon in human, equine, and canine lineages. This has caused pandemics, but only a limited number have occurred, so it is difficult to predict when the next will happen.
People who are infected can transmit influenza viruses through breathing, talking, coughing, and sneezing, which spread respiratory droplets and aerosols that contain virus particles into the air. A person susceptible to infection can then contract influenza by coming into contact with these particles.
Aerosols are smaller and remain suspended in the air longer, so they take longer to settle and can travel further than respiratory droplets.
Influenza is usually transmissible from one day before the onset of symptoms to 5Ч7 days after. In children and the immunocompromised, the virus may be transmissible for several weeks. In long-term care facilities, the flu can spready rapidly after it is introduced. In humans, influenza viruses first cause infection by infecting epithelial cells in the respiratory tract.
Illness during infection is primarily the result of lung inflammation and compromise caused by epithelial cell infection and death, combined with inflammation caused by the immune system's response to infection. Non-respiratory organs can become involved, but the mechanisms by which influenza is involved in these cases is unknown. Severe respiratory illness can be caused by multiple, non-exclusive mechanisms, including obstruction of the airways, loss of alveolar structure, loss of lung epithelial integrity due to epithelial cell infection and death, and degradation of the extracellular matrix that maintains lung structure.
In particular, alveolar cell infection appears to drive severe symptoms since this results in impaired gas exchange and enables viruses to infect endothelial cells, which produce large quantities of pro-inflammatory cytokines. Pneumonia caused by influenza viruses is characterized by high levels of viral replication in the lower respiratory tract, accompanied by a strong pro-inflammatory response called a cytokine storm. Host mechanisms to encourage tissue repair may what is the current fashion allow bacterial infection.
Infection also induces production of systemic glucocorticoids that can reduce inflammation to preserve tissue integrity but allow increased bacterial growth. The pathophysiology of how long do bailiffs take to evict a tenant is significantly influenced by which receptors influenza viruses bind to during entry into cells.
For mammalian influenza viruses and low pathogenic AIVs, cleavage is extracellular, which limits infection to cells that have the appropriate proteases, whereas for highly what spirit animal do i have AIVs, cleavage is intracellular and performed by ubiqutious proteases, which allows for infection of a greater variety of cells, thereby contributing to more severe disease.
Cells possess sensors to detect viral RNA, which can then induce interferon production. Interferons mediate expression of antiviral proteins and proteins that recruit immune cells to the infection site, and they also notify nearby uninfected cells of infection. Some infected cells release pro-inflammatory cytokines that recruit immune cells to the site of infection.
Immune cells control viral infection by killing infected cells and phagocytizing viral particles and apoptotic cells. An exacerbated immune response, however, can harm the host organism through a cytokine storm. B cellsa type of white blood cell, produce antibodies that bind to influenza antigens HA and NA or HEF  and other proteins to a lesser degree. Once bound to these proteins, antibodies block virions from binding to cellular receptors, neutralizing the virus.
Annual vaccination is the primary and most effective way to prevent influenza and influenza-associated complications, especially for high-risk groups.
Signs and Symptoms
Both COVID and flu can have varying degrees of signs and symptoms, ranging from no symptoms (asymptomatic) to severe symptoms. Common symptoms that COVID and flu share include: Fever or feeling feverish/chills; Cough; Shortness of breath or difficulty breathing; Fatigue (tiredness) Sore throat; Runny or stuffy nose; Muscle pain or body aches; Headache. Aug 31, †Ј The symptoms of flu can include fever or feeling feverish/chills, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches and fatigue (tiredness). Cold symptoms are usually milder than the symptoms of flu. People with colds are more likely to have a runny or stuffy nose. Aug 30, †Ј Flu symptoms range from mild to severe and can include fever, chills, achy muscles, sore throat, cough, and headache. The flu is often confused with the common cold, but flu symptoms develop more.
It can cause mild to severe illness, and at times can lead to death. This page provides resources about flu symptoms, complications, and diagnosis. Some of the symptoms of flu and COVID are similar, making it hard to tell the difference between them based on symptoms alone. Flu signs and symptoms usually come on suddenly.
People who are sick with flu often feel some or all of these symptoms:. Skip directly to site content Skip directly to page options Skip directly to A-Z link. Influenza Flu. Section Navigation. Facebook Twitter LinkedIn Syndicate. Minus Related Pages. Flu ChatBot Get answers about Flu. Flu Testing. The Difference Between Cold and Flu. Learn More. Additional Resources. Communication Resources. What CDC Does. To receive weekly email updates about Seasonal Flu, enter your email address: Email Address.