Symptoms of influenza A tend to be similar regardless of subtype. The most common are runny nose, sore throat, fever, chills, body aches, and fatigue. The main difference is their severity. Type A symptoms often come on stronger and sometimes result in hospitalization or even death. According to CDC. However, it still has the potential to increase in severity, causing hospitalization and death, particularly in children.
A physical exam is the first step. If the provider identifies common flu signs and symptoms and there is circulating flu activity in the local community, he or she will likely order a test to confirm the diagnosis.
The fastest and most common test is a rapid influenza diagnostic test RIDT. Results take 10 to 15 minutes, but they might be less accurate than other tests. Rapid molecular assays are also common in-office tests. They take slightly longer but are more accurate than some RIDTs in that there is a less chance of a test producing a false negative or false positive.
If a provider suspects a novel virus, he or she should discuss the possibility of a reverse transcription-polymerase chain reaction RT-PCR test with local and state health departments. Viral culture is also another available test that is generally not used for clinical decision-making, but for a more extensive evaluation of viruses.
Culture is most often used for monitoring of potentially novel influenza A or B viruses that might be considered for the next flu season vaccines. Like type A, the diagnosis begins with a physical examination, which can sometimes be enough to make a diagnosis. But a test is often necessary for confirmation. Consequently, a doctor might order a more robust test if they suspect a type B infection.
Unfortunately, no treatment will completely eradicate the flu virus. But there are ways to manage its symptoms and reduce its duration.
Most people simply hunker down with home remedies like lots of fluids, plenty of rest, homemade chicken soup, and pain relievers like ibuprofen Motrin and acetaminophen Tylenol. 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.
Influenza A viruses are divided into subtypes based on two proteins on the surface of the virus: hemagglutinin H and neuraminidase N. There are 18 different hemagglutinin subtypes and 11 different neuraminidase subtypes H1 through H18 and N1 through N11, respectively.
Reassortment can occur when two influenza viruses infect a host at the same time and swap genetic information. This graphic shows the two types of influenza viruses A and B that cause most human illness and that are responsible for flu seasons each year. Both influenza A and B viruses can be further classified into clades and sub-clades which are sometimes called groups and sub-groups.
Note that this graphic is an example, and currently circulating influenza clades and subclades may differ from those presented here. Figure 1 — This is a picture of a phylogenetic tree. Each sequence from a specific influenza virus has its own branch on the tree. The degree of genetic difference between viruses is represented by the length of the horizontal lines branches in the phylogenetic tree.
The further apart viruses are on the horizontal axis of a phylogenetic tree, the more genetically different the viruses are to one another.
An influenza clade or group is a further subdivision of influenza viruses beyond subtypes or lineages based on the similarity of their HA gene sequences. See the Genome Sequencing and Genetic Characterization page for more information. Clades and subclades are shown on phylogenetic trees as groups of viruses that usually have similar genetic changes i. Lee says. Thus far, the vaccine has been most effective in protecting against the influenza A H1N1 and influenza B viruses, so there is still room for improvement in preventing influenza A H3N2 viruses.
The effectiveness of the flu vaccine varies from year to year and also may depend upon the age and health of the person receiving the vaccine. Does the flu shot for one strain help minimize the effects from a flu infection caused by another strain? Although scientists can classify and monitor the different types of flu viruses, it is virtually impossible for them to develop effective vaccines that provide lifelong immunity. The reason: Flu viruses mutate change their genetic structure and replicate produce new, identical copies of themselves extremely quickly, making it difficult for scientists to keep up.
The good news is most people will recover from the flu on their own. If you have a severe case of the flu, you should see your healthcare provider. Not sure if you have the flu? A good indication of whether or not you have the flu is if a thermometer indicates you have a fever.
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