What Is The Flu Pathogen

What To Expect With Influenza

Symptoms of the flu can hit very quickly and may last several weeks. A bout of the flu typically follows this pattern:

• Days 13: Sudden appearance of fever, headache, muscle pain and weakness, dry cough, sore throat and sometimes a stuffy nose.
• Day 4: Fever and muscle aches decrease. Hoarse, dry or sore throat, cough and possible mild chest discomfort become more noticeable. You may feel tired or flat.
• Day 8: Symptoms decrease. Cough and tiredness may last one to two weeks or more.

Flu Symptoms In Adults

Flu-related fever appears in adults and can be severe. For many adults, a sudden high fever is the earliest symptom of the flu. It can also be a sign of COVID-19.

Adults rarely spike a fever unless they have a serious infection. The flu virus causes an abrupt high temperature thats greater than 100°F .

Other viral infections, like a cold, may cause low-grade fevers.

Beyond this, children and adults share many of the same symptoms. Some people may experience one or several symptoms more than another person. Each person will be different.

Flu Symptoms In Children

Flu symptoms in school-age children and adolescents are similar to those in adults. Children tend to have higher temperatures than adults, ranging from 103°F to 105°F. Flu in preschool children and infants is hard to pinpoint since its symptoms are so similar to infections caused by other viruses.

If the symptoms mentioned above are present and the flu is circulating in your area, please contact a healthcare provider immediately.

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Clinical Course Of Disease

Influenza is an acute respiratory disease characterized in its full form by the sudden onset of high fever, coryza, cough, headache, prostration, malaise, and inflammation of the upper respiratory tree and trachea. In most cases, pneumonic involvement is not clinically prominent. Acute symptoms and fever often persist for 7 to 10 days. Weakness and fatigue may linger for weeks. Influenza usually occurs in winter outbreaks or epidemics . People of all ages are afflicted, but the prevalence is greatest in school-age children disease severity is greatest in infants, the aged, and those with underlying illnesses. Croup can be a serious complication in small children. Influenza A and B viruses are the most common causes of influenza-like illness , but other pathogens also cause ILI, including influenza C viruses, parainfluenza viruses, respiratory syncytial viruses, and Mycoplasma pneumoniae. At the peak of an influenza epidemic, approximately one-third of isolates from patients with ILI will be positive for influenza A .

People with chronic pulmonary or cardiac disease, or diabetes mellitus, are at high risk of developing severe complications from influenza A viruses, which may include hemorrhagic bronchitis, pneumonia , and death. Hemorrhagic bronchitis and pneumonia can develop within hours. Fulminant fatal influenza viral pneumonia occasionally occurs dyspnea, cyanosis, hemoptysis, pulmonary edema, and death may proceed in as little as 48 hours after the onset of symptoms.

Experimental Animal Models Of Influenza Virus Infection

The use of nonhuman primates for human influenza virus infection has also been recently reevaluated. Burnet reported experimental influenza virus infection of cynomolgus monkeys in 1941 with a variant of A/WS/33 . He reported histopathologic findings of bronchopneumonia, with necrotizing bronchiolitis, intraalveolar edema and fibrin, and a mixed inflammatory infiltrate. Murphy and colleagues published a series of studies on experimental influenza virus infection in various nonhuman primates in the 1980s . Recently, Baskin et al. reported the pathology of a pigtail macaque infected with a contemporary human H1N1 influenza virus, and Baas et al. analyzed host gene expression profiles in these animals. They found histopathologic findings comparable to human influenza virus pneumonia with intraalveolar edema and interstitial inflammatory cell infiltrates, and changes including alveolar epithelial hyperplasia at day seven.

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What Is The Best Treatment

Neuraminidase inhibitorsoseltamivir, zanamivir

• Oral oseltamivir and orally inhaled zanamivir, which requires use of a specific device , are inhibitory for almost all currently circulating strains of influenza A and B viruses. Prospective randomized controlled trials show that their early therapeutic use in ambulatory patients with febrile influenza illness reduces the duration of illness, time to resume usual activities, and the risk of physician-diagnosed respiratory complications leading to antibiotic use. This includes the risk of new otitis media diagnoses in young children and, acute bronchitis in adults.

• Observational studies indicate that oseltamivir treatment reduces the likelihood of pneumonia, hospitalization and mortality, and the duration of hospitalization in those hospitalized with seasonal or pandemic 2009 H1N1 pdm09) virus infection. Mortality reduction in those hospitalized, even when treatment has been initiated as late as 5 days after illness onset. Treatment appears to reduce the likelihood of progression to pneumonia and death in risk groups like pregnant women, and in severely immunocompromised hosts, including hematopoietic stem cell and solid organ transplant recipients. However, progressive illness and mortality due to inadequately controlled viral replication, bacterial suprainfection, deteiroration in underlying conditions, or other complications may occur despite early antiviral treatment.

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What Is An Influenza Pandemic

An influenza pandemic is a worldwide outbreak of disease. This occurs when an influenza virus undergoes an antigenic shift and creates a completely new subtype of influenza A with the ability to cause illness in people and spread easily from person-to-person.

We are not currently experiencing an influenza pandemic. However, two identified avian influenza viruses have the potential to cause a pandemicH5N1 and H7N9. Because H5N1 and H7N9 do not circulate in humans, people have little to no immunity against these viruses. Human infections with these viruses have happened rarely, but if either virus changes in such a way that it is able to infect humans easily and spread easily from person-to-person, an influenza pandemic could result.

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Why Do People Usually Get The Flu In Winter

Many things may play a role:

• The virus lives longer indoors in winter, because the air is less humid than outside.
• While itâs alive and in the air, itâs easy for people to inhale it, or for it to land on the eyes, nose, or mouth.
• We spend more time indoors and have closer contact with each other, which makes it easier for the virus to spread.

Are There Other Ways To Prevent The Infection

To prevent the transmission of influenza use the following hygiene practices:

• Wash hands after contact with respiratory droplets and contaminated objects.
• Cover your mouth and nose with your arm when coughing or sneezing.
• Use tissues to contain respiratory droplets.
• Keep your hands away from your face .
• Clean commonly touched surfaces such as door knobs, or light switches. Regular household cleaners and disinfectants are appropriate.
• If you think you are sick, stay home.

Good personal hygiene practices will reduce the risk of infection. However, the most effective method of prevention is vaccination.

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Flu Symptoms & Complications

• What are emergency warning signs of flu sickness?

Influenza can cause mild to severe illness, and at times can lead to death. Flu symptoms usually come on suddenly. People who have flu often feel some or all of these symptoms:

• fever* or feeling feverish/chills
• some people may have vomiting and diarrhea, though this is more common in children than adults.

*Its important to note that not everyone with flu will have a fever.

This video includes common signs and symptoms of flu.

Should I Worry About Catching Bird Flu

People in the United States have less to fear than people who live abroad. Most of the illnesses associated with bird flu have been reported in Asian countries among people who have had close contact with farm birds. Also, people are not able to catch the bird flu virus by eating cooked chicken, turkey, or duck. High temperatures kill the virus.

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Histopathologic Changes In H5n1 Highly Pathogenic Avian Influenza Infections

Since 2003, 328 documented cases of human H5N1 influenza viral infection have been reported , with 200 fatalities. To et al. described the autopsy findings of two of the six individuals who died in the initial H5N1 human outbreak in Hong Kong in 1997. Both had clinical courses of greater than one month, with deaths attributed to multi-organ failure. The findings in the respiratory tree consisted of extensive hemorrhage, organizing diffuse alveolar damage with interstitial fibrosis, and cystically dilated air spaces. One case showed an interstitial lymphoplasmacytic infiltrate and scattered histiocytes with reactive hemophagocytic activity. All these features are compatible with late-stage cases described by Winternitz et al. in their review of 1918 pandemic autopsies . Neither case showed evidence of a secondary bacterial pneumonia. Both, however, showed a reactive hemophagocytic syndrome in hematopoietic organs, which the authors postulated may have been triggered by reactive hypercytokinemia.

Transmitted Via Close Contact And Surfaces

Its also believed to spread by contact with an infected persons clothing, bedding, towels, sheets, toys, books or other nonporous surfaces, similar to Monkeypox, said Glatter.

He added that while the tomato flu virus may be a variant or after-effect of hand foot and mouth disease, there is no evidence the disease is airborne or even droplet spread based on the Lancet report.

Glatter also believes chikungunya and dengue, both endemic to the region, could place both older adults and young children at risk for the tomato virus.

Because their immune systems may not be as robust after recovering from these mosquito-borne viruses, he said.

Glatter confirmed that there is currently no vaccine or antiviral medication available to treat this disease. However, much can be done to relieve someones discomfort until the infection resolves.

Supportive care including acetaminophen for fever and aches, along with hydration will help patients feel better, advised Glatter. Warm compresses may help to alleviate some of the discomfort associated with the painful nature of the rash.

Newman said ways to prevent tomato flu include quick isolation of infected patients and proper hand hygiene.

She emphasized performing environmental disinfection of surfaces, toys, clothes, and other items used by sick individuals.

And limiting the sharing of these items between other children and adults, she added.

So far it isnt life threatening.

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Ciliated Pseudostratified Epitheepithelium Of Trachea And Bronchi

Early structural changes caused by influenza virus in the epithelium of the upper airway are variable, including cytonecrosis initially involving shrinkage and vacuolization, followed by desquamation of these cells into the luminal space. Necrotic cells may also undergo phagocytosis by macrophages. These structural changes to the epithelium are often irregularly distributed, and regions of pathology can abut areas appearing histologically normal. The final stage of desquamation of the affected epithelium frequently shows only a single layer of flattened basalar epithelial cells covering the basement membrane. Complete separation of the remaining epithelium may be a histologic artifact. An outstanding feature in early stages of infection is the absence of neutrophils in the infiltrate, but as epithelial cell necrosis occurs, these cells migrate in. Later stages show mononuclear inflammatory cell infiltrates in the walls of bronchi .

Biology Of Influenza Viruses

Influenza viruses are enveloped negative-strand RNA viruses with segmented genomes containing seven to eight gene segments . One genus includes influenza A and B viruses, and the other comprises influenza C viruses. The three virus types differ in host range and pathogenicity. Type B and C influenza viruses are isolated almost exclusively from humans, although influenza B viruses have been isolated from seals and influenza C viruses have been isolated from pigs and dogs . Influenza A viruses, however, infect a wide variety of warm-blooded animals, including birds, swine, horses, humans, and other mammals. Avian influenza viruses in aquatic birds serve as the natural reservoir for all known subtypes of influenza A virus and probably are the ultimate source of human pandemic influenza strains . Influenza A viruses are subdivided by antigenic characterization of the hemagglutinin and NA surface glycoproteins that project from the virion. Sixteen HA and 9 NA subtypes are known .

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Can Influenza Be Prevented

Influenza can be prevented by annual vaccination. In Canada, the National Advisory Committee on Immunization recommends that all Canadians older than six months get a flu shot.

The influenza vaccine is highly recommended for the following people due to a higher risk of hospitalization:

• Adults and children with chronic heart or lung disease.
• People of any age who are residents of nursing homes and other long-term care facilities.
• People over the age of 65 years.
• Children between 6 months and 5 years.
• People with health conditions such as diabetes, cancer, heart disease, lung disease, obesity, etc.
• Healthy pregnant women.
• Indigenous peoples.

The vaccine is also recommended for people who are capable of transmitting influenza to those at high risk. For example, health care workers, those providing essential community services, people who have close contact with those listed as high risk, those who care for or are expecting a newborn baby during flu season, child care workers, or those who live or work in situations that have close contact .

Types Of Influenza Viruses

This is a picture of an influenza A virus. Influenza A viruses are classified by subtypes based on the properties of their hemagglutinin and neuraminidase surface proteins. There are 18 different HA subtypes and 11 different NA subtypes. Subtypes are named by combining the H and N numbers e.g., A, A. Click on the image to enlarge the picture.

There are four types of influenza viruses: A, B, C and D. Human influenza A and B viruses cause seasonal epidemics of disease almost every winter in the United States. Influenza A viruses are the only influenza viruses known to cause flu pandemics, i.e., global epidemics of flu disease. A pandemic can occur when a new and different influenza A virus emerges that both infects people and has the ability to spread efficiently among people. Influenza C virus infections generally cause mild illness and are not thought to cause human epidemics. Influenza D viruses primarily affect cattle and are not known to infect or cause illness in people.

Conversely, when two flu viruses are antigenically similar, a hosts immune response elicited by infection or vaccination with one of the viruses will recognize and neutralize the other virus, thereby protecting against the other virus.

Influenza A viruses also change both genetically and antigenically. Influenza A viruses have formed many separate, genetically different clades in recent years that continue to co-circulate.

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How Does A Flu Virus Make Me Sick

Flu viruses enter the body through the mucus membranes of your nose, eyes, or mouth. Every time you touch your hand to one of these areas, you are possibly infecting yourself with a virus.

This makes it very important to keep your hands germ-free with frequent and thorough hand washing. Encourage family members to do the same to stay well and prevent flu.

Virus Isolation In Culture

Influenza viruses can be isolated in culture from a range of specimens taken from the upper and lower respiratory tract preferred specimen types are nasopharyngeal or nasal swabs and nasal washes or aspirates. Recently, the capital costs and longer turnaround times of culture compared with other more rapid detection systems have called into question the relevance of culture isolation methods.36 However, it is clear that virus isolation remains essential for phenotypic antiviral susceptibility testing. In addition, the isolation process can be accelerated using centrifugation-enhanced techniques.37

L.E. Davis, in, 2014

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How Influenza Affects Your Body

The flu affects your whole bodyincluding your nose, throat and lungsand can lead to serious complications in those with chronic illness.

Many people who become sick with the flu say it is like being hit by a truck. Flu symptoms, such as high fever, cough and muscle aches, usually come on suddenly and are more severe than colds. Not only does having the flu impact your daily activities, it also leads to missed days from work and school.

Complications can include pneumonia, ear or sinus infections, dehydration, and worsening of chronic medical conditions, such as congestive heart failure, asthma or diabetes.

The flu can be fatal in elderly people, people with chronic diseases and anyone with a weak immune system.

Learn more about the connection between the flu and pneumonia.

What Common Complications Are Associated With Infection With This Pathogen

• Respiratory complications. Influenza infections are associated with a wide range of complications affecting the upper and lower respiratory tracts. Tracheobronchitis is so common in patients presenting for care that may be considered part of the influenzal syndrome. These complications can be due to direct viral infection, secondary bacterial infections, or a mixed process. The distinction is very difficult without proper microbiologic studies. One study during the 2009 pandemic found that the absence of crackles on auscultation and presence of oxygen saturation greater than 96% on room air predicted the absence of pulmonary infiltrates on chest radiograph.

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Pathogen Name And Classification

Influenza viruses are segmented, negative-strand ribonucleic acid viruses in the Orthomyxoviridae family. Influenza A viruses of various subtypes infect many animal species in addition to humans. Influenza A viruses are classified into subtypes by their surface glycoproteins with 17 hemagglutinin and 10 neuraminidase subtypes currently recognized. Wild aquatic birds are the primary reservoir for these many subtypes, but certain HA subtypes have adapted to and circulated widely in mammalian hosts or domestic poultry . One subtype H17N10 has been detected in bats. Influenza B and C viruses are primarily human pathogens. Influenza viruses are designated by their host source , type, location/sample, number/year of isolation, and subtype for influenza A viruses .