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Flu - Influenza

Clinical Trials  |  Add a link  |  Regulations  |  Discussion Board  |  Ask the Nurse | Last Update January 1st. 2009  |  About FDA.COM  | Media Kit

Also called: Grippe, Influenza

Flu is a respiratory infection caused by a number of viruses. The viruses pass through the air and enter your body through your nose or mouth. Between 5% and 20% of people in the U.S. get the flu each year. The flu can be serious or even deadly for elderly people, newborn babies and people with certain chronic illnesses.

Symptoms of the flu come on suddenly and are worse than those of the common cold. They may include

  • Body or muscle aches
  • Chills
  • Cough
  • Fever
  • Headache
  • Sore throat

Is it a cold or the flu? Colds rarely cause a fever or headaches. Flu almost never causes an upset stomach. And "stomach flu" isn't really flu at all, but gastroenteritis.

The main way to keep from getting the flu is to get a yearly flu vaccine. If you get the flu, your health care provider may prescribe medicine to help your body fight the infection and lessen symptoms.

National Institute of Allergy and Infectious Diseases

 

What’s the Difference Between Seasonal Flu, Pandemic Flu, and Avian (Bird) Flu?

Influenza, or flu, is a respiratory infection caused by several flu viruses. Flu viruses are classified as types A, B, and C; type A has a number of subtypes. The flu is not the same as the common cold, nor is it related to what is commonly called the “stomach flu.”

Seasonal Flu

Seasonal flu is the term used to refer to the flu outbreaks that occur yearly, mainly in the late fall and winter. It is estimated that between 5 and 20 percent of Americans come down with the flu every flu season.

Pandemic Flu

Pandemic flu refers to particularly virulent strains of flu that spread rapidly from person to person to create a world-wide epidemic (pandemic).

Avian (Bird) Flu

In nature, the flu virus also occurs in wild aquatic birds such as ducks and shore birds. It does not normally spread from birds to humans. However, pigs can be infected by bird influenza (as well as by the form of influenza that affects humans) and can pass on the flu to humans. In 1997, it was discovered that a virulent bird influenza had skipped the pig step and had infected humans directly, causing a number of deaths in Asia.

These instances of bird flu in humans have raised concerns that if this type of flu could at some point be transmitted between people, a new pandemic would occur. Thus, the term bird flu or avian flu is currently being used to refer to a possible pandemic flu.

Overview of the Flu

The flu, like the common cold, is a respiratory infection caused by viruses. But the flu differs in several ways from the common cold. For example, people with colds rarely get fevers or headaches or suffer from the extreme exhaustion that flu viruses cause. The most familiar aspect of the flu is the way it can "knock you off your feet" as it sweeps through entire communities.

The Centers for Disease Control and Prevention (CDC) estimates that 5 to 20 percent of Americans come down with the flu during each flu season, which typically lasts from November to March. Children are two to three times more likely than adults to get sick with the flu, and children frequently spread the virus to others. Although most people recover from the illness, CDC estimates that in the United States more than 200,000 people are hospitalized and about 36,000 people die from the flu and its complications every year.

Seasonal Flu Outbreaks

Seasonal flu outbreaks usually begin suddenly and occur mainly in the late fall and winter. The disease spreads through communities, creating an epidemic. During the epidemic, the number of cases peaks in about 3 weeks and subsides after another 3 or 4 weeks. Half of the population of a community may be affected. Because schools are an excellent place for flu viruses to attack and spread, families with school-age children have more infections than other families, with an average of one-third of the family members infected each year.

Importance of Flu

Besides the rapid start of the outbreaks and the large numbers of people affected, the flu is an important disease because it can cause serious complications. Most people who get the flu get better within a week (although they may have a lingering cough and tire easily for a while longer). For elderly people, newborn babies, and people with certain chronic illnesses, however, the flu and its complications can be life-threatening.

Flu Virus Characteristics

A flu virus is roughly round, but it can also be elongated or irregularly shaped. Inside are eight segments of single-strand RNA containing the genetic instructions for making new copies of the virus. Flu's most striking feature is a layer of spikes projecting from its surface. There are two different types of spikes: one is the protein hemagglutinin (HA), which allows the virus to "stick" to a cell and initiate infection, the other is a protein called neuraminidase (NA), which enables newly formed viruses to exit the host cell.

 

Microscope photo of the influenza A virus
Influenza A virus. Credit: CDC
 

Virus Types A, B, C

Influenza viruses are classified as type A, B, or C based upon their protein composition. Type A viruses are found in many kinds of animals, including ducks, chickens, pigs, and whales, and also humans. The type B virus widely circulates in humans. Type C has been found in humans, pigs, and dogs and causes mild respiratory infections, but does not spark epidemics.

Type A influenza is the most frightening of the three. It is believed responsible for the global outbreaks of 1918, 1957, and 1968. Type A viruses are subdivided into groups based on two surface proteins, HA and NA. Scientists have characterized 16 HA subtypes and 9 NA subtypes.

Naming Viral Strains

Type A subtypes are classified by a naming system that includes the place the strain was first found, a lab identification number, the year of discovery, and, in parentheses, the type of HA and NA it possesses, for example, A/Hong Kong/156/97 (H5N1). If the virus infects non-humans, the host species is included before the geographical site, as in A/Chicken/Hong Kong/G9/97 (H9N2). There are no type B or C subtypes.

Where Influenza Comes From

In nature, the flu virus is found in wild aquatic birds such as ducks and shore birds. It has persisted in these birds for millions of years and does not typically harm them. But the frequently mutating flu viruses can readily jump the species barrier from wild birds to domesticated ducks and then to chickens. From there, the next stop in the infectious chain is often pigs.

Pigs can be infected by both bird (avian) influenza and the form of influenza that infects humans. In a setting such as a farm where chickens, humans, and pigs live in close proximity, pigs act as an influenza virus mixing bowl. If a pig is infected with avian and human flu simultaneously, the two types of virus may exchange genes. Such a "reassorted" flu virus can sometimes spread from pigs to people.

Depending on the precise assortment of bird-type flu proteins that make it into the human population, the flu may be more or less severe.

In 1997, for the first time, scientists found that bird influenza skipped the pig step and infected humans directly. Alarmed health officials feared a worldwide epidemic (a pandemic). But, fortunately, the virus could not pass between people and thus did not spark an epidemic. Scientists speculate that chickens may now also have the receptor used by human-type viruses.

Drifting and Shifting

Influenza virus is one of the most changeable of viruses. These genetic changes may be small and continuous or large and abrupt.

Small, continuous changes happen in type A and type B influenza as the virus makes copies of itself. The process is called antigenic drift. The drifting is frequent enough to make the new strain of virus often unrecognizable to the human immune system. For this reason, a new flu vaccine must be produced each year to combat that year's prevalent strains.

Type A influenza also undergoes infrequent and sudden changes, called antigenic shift. Antigenic shift occurs when two different flu strains infect the same cell and exchange genetic material. The novel assortment of HA or NA proteins in a shifted virus creates a new influenza A subtype. Because people have little or no immunity to such a new subtype, their appearance tends to coincide with a very severe flu epidemic or pandemic.

 

Reference Links - Add a link

Clinical Trials - Add a clinical trial

 top
1
Recruiting
High-Dose Vs. Standard-Dose Oseltamivir (Tamiflu) to Treat Severe Influenza and Avian Influenza
Conditions:
Avian Influenza;   Severe Influenza 
Intervention:
Drug: Oseltamivir 
 
 

 
2
Recruiting
Study to Evaluate the Consistency of Three Consecutive Production Lots of Influenza Vaccine in Healthy Subjects 18 to 49 Years Old
Condition:
Influenza 
Interventions:
Biological: Trivalent Subunit Influenza Vaccine;   Biological: Trivalent Subunit Influenza Vaccine;   Biological: Trivalent Subunit Influenza Vaccine;   Biological: Egg-derived trivalent subunit influenza vaccine 
 
 

 
3
Recruiting
Safety and Immunogenicity of Two Doses of a Tetravalent Influenza Vaccine in Adults Aged 18 Years and Above
Condition:
Influenza 
Interventions:
Biological: Tetravalent, placebo and pandemic influenza vaccine;   Biological: Pandemic influenza vaccine,placebo and tetravalent;   Biological: Pandemic influenza vaccine plus seasonal influenza vaccine;   Biological: Tetravalent plus placebo, placebo and pandemic influenza vaccine;   Biological: Pandemic influenza vaccine, placebo and tetravalent;   Biological: Pandemic influenza vaccine plus seasonal influenza vaccine 
 
 

 
4
Recruiting
Clinical Study in Children, 6 Months to 3 Years of Age, to Assess Two Dose Levels of an Experimental Flu Vaccine, Using a Licensed Influenza Virus Vaccine, Vaxigrip® as the Control
Condition:
Influenza Virus 
Interventions:
Biological: GSK Biologicals' influenza vaccine GSK1557482A;   Biological: Vaxigrip 
 
 

 
5
Recruiting
Safety and Immunogenicity of Two 0.25 mL or 0.5 mL Doses of Two Different Influenza Vaccines in Healthy Children Aged 6 to <60 Months
Condition:
Influenza 
Interventions:
Biological: Influenza Trivalent Inactivated vaccines Novartis;   Biological: Influenza Trivalent Inactivated vaccines 
 
 

 
6
Not yet recruiting
Zanamivir Versus Trivalent Split Virus Influenza Vaccine
Condition:
Influenza 
Interventions:
Biological: Fluviral;   Drug: Zanamivir 
 
 

 
7
Recruiting
Immunogenicity, Safety and Tolerability of Prepandemic Influenza and Seasonal Influenza Vaccine in Adult Subjects
Conditions:
Pandemic;   Avian Influenza 
Intervention:
Biological: H5N1, avian influenza vaccine 
 
 

 
8
Recruiting
Second Extension Study to Evaluate Safety and Tolerability of Influenza Vaccines in Adults and Elderly, and to Evaluate Immunogenicity and Concomitant Vaccination With Pneumococcal Vaccine in a Subgroup
Condition:
Influenza Disease 
Interventions:
Biological: FCC;   Biological: Egg-derived influenza vaccine;   Biological: FCC + Pneumococcal vaccine;   Biological: Egg-derived influenza vaccine + Pneumococcal vaccine 
 
 

 
9
Recruiting
Trial to Evaluate the Efficacy of GSK Biologicals' Influenza Vaccine GSK2186877A in Adults 65 Year of Age and Older
Condition:
Influenza Disease 
Interventions:
Biological: GSK Bio's influenza vaccine GSK2186877A;   Biological: Fluarix 
 
 

 
10
Recruiting
Development of Immune Globulin Treatment for Avian Flu
Conditions:
Infectious Diseases;   Influenza;   Avian Flu 
Interventions:
Drug: H5N1 Vaccine;   Procedure: Apheresis 
 
 

 
11
Recruiting
Safety, Tolerability, Immunogenicity And CPG Dosage Finding Study of Novartis CpG Adjuvanted Flu Vaccine
Condition:
Influenza Infection 
Interventions:
Biological: Subunit influenza vaccine;   Biological: Adjuvanted influenza vaccine;   Biological: Adjuvanted influenza vaccine combined with CpG7909;   Biological: Adjuvanted influenza vaccine combine with CpG7909;   Biological: Adjuvanted influenza vaccine combine with CpG7909 
 
 

 
12
Recruiting
Immunogenicity, Safety and Tolerability of Two Doses of a Pre-Pandemic Influenza Vaccine in Participants Aged 6 Months to 17 Years
Condition:
Prophylaxis of Avian Influenza 
Intervention:
Biological: avian influenza vaccine 
 
 

 
13
Recruiting
 

 
14
Recruiting
A Study to Determine the Immunogenicity and Safety of CSL Limited's Influenza Virus Vaccine Compared to a US Licensed Comparator Influenza Virus Vaccine
Condition:
Influenza 
Interventions:
Biological: CSL Limited Influenza Virus Vaccine;   Biological: US Licensed Influenza Virus Vaccine 
 
 

 
15
Recruiting
Safety and Immunogenicity of a Booster Dose of -H5N1 Influenza Vaccine
Condition:
Avian Influenza 
Interventions:
Biological: H5N1 influenza muffin;   Biological: H5N1 influenza vaccine 
 
 

 
16
Not yet recruiting
High Dose Influenza in Immunosuppressed Subjects
Condition:
Influenza 
Interventions:
Biological: TIV;   Biological: rHAO Trivalent Influenza Vaccine 
 
 

 
17
Recruiting
Phase III Study of a H5N1 Vaccine in Adults, Elderly and Specified Risk Groups
Condition:
Influenza 
Interventions:
Biological: H5N1 Influenza Vaccine Whole virion, Vero cell-derived, Inactivated Influenza Vaccine, non-adjuvanted;   Biological: H5N1 Influenza Vaccine Whole virion, Vero cell-derived, Inactivated Influenza Vaccine, non-adjuvanted 
 
 

 
18
Recruiting
Dose Ranging Study to Evaluate Immunogenicity and Safety of Adjuvanted or Non-Adjuvanted Cell Culture-Derived H5N1 Influenza Vaccine in Young Adults (18-40 Years Old)
Condition:
Influenza 
Interventions:
Biological: FCC H5N1 3,75 µg;   Biological: FCC H5N1 7,5 µg;   Biological: FCC H5N1 15 µg;   Biological: FCC H5N1 3,75 µg + 25% MF59;   Biological: FCC H5N1 7,5 µg + 25% MF59;   Biological: FCC H5N1 15 µg + 25% MF59;   Biological: FCC H5N1 3,75 µg + 50% MF59;   Biological: FCC H5N1 7,5 µg + 50% MF59;   Biological: FCC H5N1 15 µg + 50% MF59;   Biological: FCC H5N1 3,75 µg + 100% MF59;   Biological: FCC H5N1 7,5 µg + 100% MF59;   Biological: FCC H5N1 15 µg + 100% MF59 
 
 

 
19
Recruiting
PET-CT Scans in Healthy Volunteers After Flu Vaccination
Condition:
Immune Response to Influenza Vaccination 
Intervention:
Biological: FluShield, FluMist 
 
 

 
20
Recruiting
FLU A+B Nasal Swab Clinical Study
Condition:
Influenza 
Intervention:
Other: Non-invasive diagnostic testing 
 
 

 
21
Recruiting
Flumist & Herd Immunity for Flu Control
Condition:
Influenza 
Intervention:
Biological: LAIV 
 
 

 
22
Recruiting
Influenza Vaccine in Premature Infants
Conditions:
Influenza;   Infant, Premature 
Intervention:
Biological: Trivalent Inactivated Influenza Vaccine 
 
 

 
23
Not yet recruiting
Randomized Control Trial to Study the Efficacy of the Surgical Mask Versus the N95 Respirator to Prevent Influenza
Condition:
Influenza 
Interventions:
Device: Surgical mask;   Device: N95 mask 
 
 

 
24
Recruiting
Influenza Vaccine in Lung Transplant Patients
Condition:
Influenza 
Intervention:
Drug: Influenza vaccine 
 
 

 
 
26
Not yet recruiting
Inactivated Influenza A/H5N1 Vaccine in Adult Subjects at Risk of Occupational Exposure to Live H5N1 Viruses
Condition:
Influenza 
Intervention:
Biological: inactivated influenza A/H5N1 vaccine 
 
 

 
 
28
Recruiting
Clinical Study of the Immunogenicity of GSK Biologicals' Influenza Vaccine GSK2186877A in People Aged 65 Years or Older
Condition:
Influenza Infection 
Interventions:
Biological: GSK Biologicals' Fluarix;   Biological: GSK Biologicals' influenza vaccine GSK2186877A 
 
 

 
29
Recruiting
Comparative Study of Influenza Vaccines in Adults, FLUVACS-Year 4
Condition:
Influenza 
Interventions:
Biological: Fluzone;   Biological: Flumist;   Other: Physiologic saline 
 
 

 
30
Recruiting
Direct and Indirect Benefits of Influenza Vaccine Versus Placebo in Healthy Children
Condition:
Influenza Virus Infection 
Interventions:
Biological: Inactivated influenza vaccine;   Biological: Saline 
 
 

 
31
Recruiting
T-Cell Response-Flu Risk in Older Adults
Condition:
Influenza 
Intervention:
Biological: Commercial TriValent Split Influenza Virus 
 
 

 
32
Recruiting
Safety and Immunogenicity of a Monovalent Conjugated Vaccine Against Haemophilus Influenzae Type b
Condition:
Haemophilus Influenzae Type B 
Interventions:
Biological: Haemophilus influenzae type b vaccine;   Biological: Commercial Haemophilus influenzae type b vaccine 
 
 

 
33
Recruiting
An Open-Label, Randomized Phase I Study in Healthy Adults of 4 Prime-Boost Schedules With Monovalent Influenza Subunit Virion (H5N1) Vaccine (Sanofi Pasteur, Inc), Administered Alone or Following Recombinant DNA Plasmid (H5) Vaccine (VRC, NIAID)
Conditions:
Influenza A Virus, H5N1 Subtype;   Influenza A Virus;   Influenzavirus A;   Orthomyxoviridae;   H5N1 Virus 
Interventions:
Drug: Monovalent Influenza Subunit Virion (H5N1) Vaccine, A/Indonesia/05/2005;   Drug: VRC-AViDNA036-00-VP 
 
 

 
34
Recruiting
Immunogenicity & Safety of GSK's Avian Flu Vaccine 1557484A Given to Adults Aged 18-64 Years.
Condition:
Influenza Disease Caused by an Influenza A Virus With Pandemic Potential, Sub-Type H5N1 
Intervention:
Biological: GSK influenza virus H5N1 vaccine 1557484A 
 
 

 
35
Recruiting
Influenza Vaccine Postpartum Questionnaire
Conditions:
Influenza;   Vaccine;   Pregnancy 
Intervention:
 
 
 

 
36
Not yet recruiting
Heterosubtypic Immune Responses to Influenza in Older People
Condition:
Influenza 
Interventions:
Biological: Seasonal vaccine;   Biological: H5 vaccine 
 
 

 
37
Recruiting
TGV:Use of the Quick Diagnostic Test of the Influenza and the Infection With RSV by the Paediatric Emergency Unit
Conditions:
Influenza;   Respiratory Syncytial Viruses 
Intervention:
Device: RSV respi-strip and Quick-vue influenza 
 
 

 
38
Recruiting
Safety and Immunogenicity Study of Adenovirus-Vectored, Intranasal Pandemic Influenza Vaccine.
Condition:
Pandemic Influenza 
Intervention:
Biological: Pandemic Influenza Vaccine 
 
 

 
39
Recruiting
Prospective Trial of Vaccine Responses Against Pneumococcus and Influenza in Adult Cancer Patients 65 Years of Age and Older
Conditions:
Breast Cancer;   Lung Cancer;   Prostate Cancer 
Interventions:
Biological: inactivated influenza vaccine and the 23- valent pneumococcal vaccine;   Biological: inactivated influenza vaccine and the PPV23 vaccine (Pneumovax) 
 
 

 
40
Recruiting
Intradermal Versus Intramuscular Trivalent Influenza Vaccine in Adult Lung Transplant Recipients
Conditions:
Influenza Virus;   Influenza Vaccine 
Intervention:
Biological: Vaxigrip (Aventis-Pasteur Canada) 
 
 

 
41
Recruiting
Stopping Upper Respiratory Infections and Flu in the Family: The Stuffy Trial
Conditions:
Respiratory Tract Infections;   Common Cold 
Interventions:
Behavioral: Hand hygiene and educational material;   Device: Mask, alcohol and hand sanitizer 
 
 

 
42
Recruiting
Needle-Free Jet Injection of Reduced-Dose, Intradermal, Influenza Vaccine in >= 6 to < 24-Month-Old Children
Condition:
Influenza 
Interventions:
Biological: Vaxigrip® trivalent inactivated influenza vaccine;   Device: Intradermal spacer on Biojector® 2000 jet injector 
 
 

 
43
Recruiting
Catechin Containing Mask for the Prevention of Influenza Infection
Condition:
Influenza Infection 
Intervention:
Dietary Supplement: tea catechin extracts 
 
 

 
44
Recruiting
Th1 Response to Influenza: Aging and Vaccine Efficacy
Condition:
Influenza 
Interventions:
Drug: Placebo;   Biological: Trivalent Inactivated Influenza 
 
 

 
45
Not yet recruiting
Study to Evaluate Nosocomial Transmission of Influenza
Condition:
Influenza 
Intervention:
 
 
 

 
46
Recruiting
REDucing Influenza Among University Students, University of California at Berkeley
Conditions:
Influenza-Like Illness;   Influenza 
Intervention:
Behavioral: Online education 
 
 

 
47
Recruiting
Annual Study for Serum Collection for Immunogenicity and Safety Evaluation in Healthy Children Receiving Fluzone®
Conditions:
Influenza;   Orthomyxoviridae Infections 
Interventions:
Biological: Influenza Virus Vaccine No Preservative: Pediatric Dose;   Biological: Influenza Virus Vaccine No Preservative: Pediatric Dose 
 
 

 
48
Not yet recruiting
Evaluation of Efficacity and Safety of Oseltamivir and Zanamivir
Condition:
Influenza Disease 
Interventions:
Drug: oseltamivir + zanamivir;   Drug: oseltamivir + zanamivir's placebo;   Drug: oseltamivir's placebo + zanamivir 
 
 

 
49
Recruiting