Where Does The Flu Come From Every Year
A computer model developed by scientists at the University of Chicago shows that small increases in transmission rates of the seasonal influenza A virus can lead to rapid evolution of new strains that spread globally through human populations. The results of this analysis, published September 13, 2016 in the Proceedings of the Royal Society B, reinforce the idea that surveillance for developing new, seasonal vaccines should be focused on areas of east, south and southeast Asia where population size and community dynamics can increase transmission of endemic strains of the flu.
“The transmissibility is a feature of the pathogen, but it’s also a feature of the host population,” said Sarah Cobey, PhD, assistant professor of ecology and evolution at the University of Chicago and senior author of the study. “So a host population that potentially has more crowding, larger classroom sizes for children, or even certain types of social contact networks, potentially sustains higher transmission rates for the same virus or pathogen.”
There are four influenza strains that circulate in the human population: A/H3N2, A/H1N1, and two B variants. These viruses spread seasonally each year because of a phenomenon known as antigenic drift: They evolve just enough to evade human immune systems, but not enough to develop into completely new versions of the virus.
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.
Influenza B Strain Comes Early To Nova Scotia
“What’s really unusual is we’re seeing early influenza B activity,” Strang said.
The influenza B strain is normally less severe and usually doesn’t spike until the end of the flu season.
“It may be contributing to an increased number of cases right now, because with two strains circulating, the same person could get influenza A and influenza B,” he said.
“It might also mean that our flu season will end sooner … but only time will tell about that.”
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How Many Types Of Influenza Are There
Scientists have, for now, identified four different influenza types, named A, B, C and D.
Human influenza A and B viruses are the most common. These are the bugs that cause the seasonal flu epidemics quite predictably each winter in the United States and around the world. Most flu vaccines protect against these two types.
How Viruses Mutate And Create New Variants
UPDATE: Resources and information on COVID-19 testing and more.
As the COVID-19 pandemic continues, new variants of the SARS-CoV-2 virus pop up, and some lead to increasing infections. The main new variantsnamed Alpha, Beta, and Delta and first identified in Britain, South Africa, and India, respectivelyhave properties that make them more successful in transmitting and replicating than the original virus.
Viruses are not technically living thingsthey invade living cells and hijack their machinery to get energy and replicate, and find ways to infect other living organisms and start the process over again.
How viruses mutate largely has to do with how they make copies of themselves and their genetic material, says , an associate professor of molecular biology and microbiology at the School of Medicine. Viruses can have genomes based on DNA or RNAunlike human genomes, which are made up of DNA, which then can create RNA.
Gaglia studies how viruses take control of infected cells and reprogram the cells machinery to reproduce themselves. Weve been working on a protein that the virus encodes that destroys the host RNA, blocking the cells from being able to express their own protein and blocking, among other things, antiviral response, she says.
Tufts Now talked with Gaglia to learn more about how different viruses mutate and what it might mean for the COVID-19 virus and vaccines ability to stop its transmission.
Are there different varieties of virus genomes?
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Caring For Babies And Children
When a baby or child has influenza, it is important to do the following:
- keep the child at home resting until they are well.
- care for the child in a separate, well-ventilated room away from other people.
- increase the frequency of breastfeeding or the amount of other fluids they drink. If your child will not take fluids or is drowsy, dont force them. Seek medical advice immediately.
- reduce fever by using a damp cloth on their forehead, washing their arms and body with a cool cloth, bathing them in slightly warm water.
- give paracetamol or ibuprofen if they have pain or discomfort in the dose recommended on the package . Aspirin should not be given to children under 14 years of age.
Saltwater drops can be used to treat a stuffy nose.
Antigenic Drift And Shift
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 gene. This can occur in response to evolutionary pressure exerted by the host immune response. Antigenic drift is especially common for the HA protein, in which just a few amino acid changes in the head region can constitute antigenic drift. The result is the production of novel strains that can evade pre-existing antibody-mediated immunity. Antigenic drift occurs in all influenza species but is slower in B than A and slowest in C and D. Antigenic drift is a major cause of seasonal influenza, and requires that flu vaccines be updated annually. 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.
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How Many Coronaviruses Are There
Coronaviruses didn’t just pop up recently. They’re a large family of viruses that have been around for a long time. Many of them can cause a variety of illnesses, from a mild cough to severe respiratory illnesses.
The new coronavirus that causes COVID-19 is one of several known to infect humans. It’s probably been around for some time in animals. Sometimes, a virus in animals crosses over into people. That’s what scientists think happened here. So this virus isn’t new to the world, but it is new to humans. When scientists found out that it was making people sick in 2019, they named it as a novel coronavirus. Experts call these strains SARS-CoV-2.
What Was The Impact Of The 1918 Flu Pandemic In Canada
The pandemic brought not only death but social and economic disruption as well. Children were left parentless and many families found themselves without their chief wage earner. Armies on both sides of the First World War were temporarily debilitated. Businesses lost profits because of lack of demand for their products or because they were unable as a result of a reduced work force to meet the demand. Municipal governments, in an attempt to halt the spread of the disease, closed all except necessary services. Provinces enacted laws regarding quarantine and enforced the wearing of masks in public. Although the Canadian population unhappily accepted these restrictions, it defied the federal governments request that First World War victory celebrations be postponed until 1 December 1918. The establishment of the federal Department of Health in 1919 was a direct result of the Canadian epidemic.
The influenza strain, although decreasingly virulent, remained active in Canada until the mid-1920s. It has since been identified as an H1N1 virus .
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Explainer: What Strains Does The 2014 Flu Vaccine Protect Against
by Raina Macintyre, The Conversation
Influenza affects up to 15% of adults and 30% of children each flu season and early indications suggest we could be facing a severe season. The 2014 seasonal influenza vaccination is available from today. So, what strains does it protect against and who should be vaccinated?
What is influenza?
Influenza is a serious viral illness that causes 1,500 to 3,500 deaths in Australia each year from complications such as pneumonia and secondary bacterial infections.
There are two major types in humans influenza A and influenza B, with the A strain causing more severe disease. Influenza B, however, causes a disproportionate amount of illness in children.
The virus also has many animal hosts including birds, pigs and horses. Genetic mixing between human and animal strains can cause new pandemic strains, to which humans have little or no pre-existing immunity. This susceptibility gives rise to rapid spread, high rates of illness and more severe disease.
Once new strains emerge in humans, they become established as seasonal variants in the population and tend to cycle over the years, with different strains dominating each year. The seasonal flu viruses we see now were once pandemic strains.
Seasonal influenza viruses mutate continually, so the vaccine needs to be updated annually to match the expected strains.
In 2014 the vaccine includes:
Should I get vaccinated?
The 2014 flu season
What Is The Bird Flu
The avian influenza virus causes bird flu. Birds can be infected by influenza A viruses and all of its subtypes. Birds are not capable of carrying either type B or C influenza viruses.
There are three main subtypes of avian flu, including H5, H7, and H9. The subtypes H5 and H7 are the most deadly, while the H9 subtype is less dangerous.
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What Are The Types Of Influenza A
As well as infecting people, the influenza A virus can infect animals, including birds and pigs . In some cases, these types of influenza can be passed on to humans.
Bird flu: Avian influenza also known as ‘bird flu’ is a subtype of influenza virus A that mainly affects birds. The virus has caused serious infections in humans and deaths but has not been found in Australia.
Swine flu: This is a type of influenza A virus found in pigs. In 2009, a strain of flu virus known as H1N1 caused the respiratory infection in humans that was commonly referred to as swine flu. It spread rapidly around the world and became a pandemic. The 1918 flu pandemic was also caused by an influenza A H1N1 virus.
Why Do I Need To Get Vaccinated Every Year
Youve probably noticed by now that we encourage our patients to get vaccinated each year. Why does this particular vaccine need to be administered again, even if you got a flu shot last year? Its because new strains of the virus are constantly appearing and evolving, so the vaccine must change along with them.
Located around the world are influenza surveillance centers that annually monitor the most common strains, collecting data and identifying new and evolving strains. Once the information has been collected, the World Health Organization selects the three strains most likely to circulate during the following flu season. This decision is typically made in February, allowing the development of a new vaccine to begin around midsummer.
Because the three strains change each year, the vaccines are formulated separately before theyre combined into the final product, the trivalent vaccine. While its usually fairly accurate, there have been instances, such as the infamous H1N1 outbreak in 2009, that required the addition of a second, separate vaccination.
In addition to the constantly evolving strains of the flu virus, your bodys immune response changes over time. Taken together, those two factors essentially render the previous years vaccinations useless against new strains. This is why its so important to get yourself vaccinated each and every year, even if you got the vaccine last year!
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The Influenza Virus And Its Genome
There are three basic types of influenza viruses: A, B, and C. Influenza B and C viruses only infect humans, so novel antigens are not introduced from other species. Only influenza A viruses infect nonhuman hosts, and a reassortment of genes can occur between those subtypes that typically infect animals and those that infect humans, resulting in antigenic shift and potential pandemics. Epidemics of seasonal influenza occur due to influenza A or B viruses.
Due to the segmented nature of the influenza genome, in which coding sequences are located on individual RNA strands, genomes are readily shuffled in host cells that are infected with more than one flu virus. For example, when a cell is infected with influenza viruses from different species, reassortment can result in progeny viruses that contain genes from strains that normally infect birds and genes from strains that normally infect humans, leading to the creation of new strains that have never been seen in most hosts. Moreover, because at least 16 different hemagglutinin subtypes and nine different neuraminidase subtypes have been characterized, many different combinations of capsid proteins are possible. Of these subtypes, three subtypes of hemagglutinin and two subtypes of neuraminidase have caused sustained epidemics in the human population. Birds are hosts for all influenza A subtypes and are the reservoir from which new HA subtypes are introduced into humans .
Would Fluzone Have Helped
This week, media stories implied that if Australia had purchased a different vaccine, Sanofi Pasteurs egg-grown inactivated Fluzone®, the massive flu epidemic would not have happened. Rubbish.
The Fluzone product being discussed is a high-dose flu vaccine licensed in the United States and Canada for those aged 65 years or older, but not for other age groups. Its not available in Australia because Sanofi hasnt applied to register it here.
This vaccine contains four times more antibody-inducing active ingredient, hemagglutinin than a standard-dose vaccine. But it remains susceptible to problems discussed earlier though this hasnt been well studied.
High-dose Fluzone is a trivalent formulation , not quadrivalent as recommended in Australia this year.
No current vaccine could have prevented 2017s flu epidemic.
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Lesson #: Influenza A Symptoms
Now that you’re ready to ace your next biology exam on flu virus nomenclature , we’re going to jump into Lesson #2: Influenza A.
Influenza A is typically responsible for those seasonal influenza epidemics that come around almost every winter. In the US, cases of seasonal flu typically spike during a few specific months of the year starting in September or October and running all the way through March or April This strain of the flu is also typically the most serious, and often has more severe symptoms than other strains, including coughing, sneezing, sore throat, fever, exhaustion, and chills and body aches.
This strain of the flu is most commonly found in humans and animals. In fact, remember that swine flu pandemic we were talking about at the beginning of this blog? Well, that virus is technically an influenza A virus, but it’s a little bit more complicated than that. That particular strain was so severe because it was a combination of swine, human, and bird flu viruses talk about a triple threat! The strain mutated so that it was no longer the same influenza A virus that our bodies are protected by through the annual flu vaccine.
Flu Mutation? Did You Really Just Say That?
Antigenic shift on the other hand is a you guessed it big ole’ shift, or change, to influenza A viruses. Such a big change, in fact, that it results in new hemagglutinin or neuraminidase proteins, meaning that the very subtype of the virus has changed completely.
What Are The Various Types Of Flu
Four main influenza viruses exist: A, B, C, and D. The different viruses are referred to as types, or strains. The human influenza virus types A and B are responsible for the illnesses experienced during the flu season every year. Influenza A caused pandemics in the past, like the Spanish flu of 1918. Influenza virus C causes mild sickness, and influenza virus D causes illnesses in cows. Influenza A viruses can also infect different animals like pigs and birds. While it is rare, some animal flu viruses can infect humans, like in past cases with the avian, or bird, flu.
Influenza A and B viruses are further classified into subgroups. Influenza A, in particular, is broken down into subtypes based on specific proteins on the virus surface: hemagglutinin and neuraminidase . You may have heard about the H1N1 or H3N2 flu viruses, which are strains of influenza A that commonly infect humans. A total of 131 subtypes of influenza A have been identified to date.
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What Are The Types Of Flu In 2021
The strains of the flu virus in circulation vary at any given time but are usually of the A or B strains. The CDC FluView Interactive surveillance platform keeps track of the activity of different influenza viruses each week.
The FDA Vaccines and Related Biological Products Advisory Committee chooses which influenza strains will be covered by the flu vaccine for the upcoming flu season. The strains chosen are based on which flu viruses are currently circulating and which ones are most likely to circulate during the upcoming flu season. The 2021-2022 flu vaccine will protect against different variations of influenza A subtypes H1N1 and H3N2 and influenza B.