Avian influenza
Fact sheet
Updated March 2014
Updated March 2014
Key facts
Avian influenza (AI), commonly called bird flu, is an infectious viral disease of birds.
Most avian influenza viruses do not infect humans; however some, such as A(H5N1) and A(H7N9), have caused serious infections in people.
Outbreaks of AI in poultry may raise global public health concerns due to their effect on poultry populations, their potential to cause serious disease in people, and their pandemic potential.
Reports of highly pathogenic AI epidemics in poultry, such as A(H5N1), can seriously impact local and global economies and international trade.
The majority of human cases of A(H5N1) and A(H7N9) infection have been associated with direct or indirect contact with infected live or dead poultry. There is no evidence that the disease can be spread to people through properly cooked food.
Controlling the disease in animals is the first step in decreasing risks to humans.
Avian influenza (AI) is an infectious viral disease of birds (especially wild water fowl such as ducks and geese), often causing no apparent signs of illness. AI viruses can sometimes spread to domestic poultry and cause large-scale outbreaks of serious disease. Some of these AI viruses have also been reported to cross the species barrier and cause disease or subclinical infections in humans and other mammals.
AI viruses are divided into 2 groups based on their ability to cause disease in poultry: high pathogenicity or low pathogenicity. Highly pathogenic viruses result in high death rates (up to 100% mortality within 48 hours) in some poultry species. Low pathogenicity viruses also cause outbreaks in poultry but are not generally associated with severe disease.
Avian influenza A(H5N1) and A(H7N9) background
The A(H5N1) virus subtype, a highly pathogenic AI virus, first infected humans in 1997 during a poultry outbreak in Hong Kong SAR, China. Since its widespread re-emergence in 2003 and 2004, this avian virus has spread from Asia to Europe and Africa and has become entrenched in poultry in some countries, resulting in millions of poultry infections, several hundred human cases, and many human deaths. Outbreaks in poultry have seriously impacted livelihoods, the economy and international trade in affected countries.
The A(H7N9) virus subtype, a low pathogenic AI virus, first infected 3 humans – 2 residents of the city of Shanghai and 1 resident of Anhui province - in March 2013. No cases of A(H7N9) outside of China have been reported. Containment measures, including the closure of live bird markets for several months, have impacted the agriculture sectors of affected countries and international trade. Continued surveillance for A(H7N9) will be necessary to detect and control the spread of the virus.
Ongoing circulation of A(H5N1) and A(H7N9) viruses in poultry, especially where endemic, continues to pose threats to public health, as these viruses have both the potential to cause serious disease in people and may have the potential to change into a form that is more transmissible among humans. Other influenza virus subtypes also circulate in poultry and other animals, and may also pose potential threats to public health.
Avian influenza A(H5N1) and A(H7N9) infections and clinical features in humans
The case fatality rate for A(H5N1) and A(H7N9) virus infections in people is much higher compared to that of seasonal influenza infections. The A(H7N9) virus particularly affects people with underlying medical conditions.
Clinical features
In many patients, the disease caused by the A(H5N1) virus follows an unusually aggressive clinical course, with rapid deterioration and high fatality. Like most emerging disease, A(H5N1) influenza in humans is not well understood.
The incubation period for A(H5N1) avian influenza may be longer than that for normal seasonal influenza, which is around 2 to 3 days. Current data for A(H5N1) infection indicate an incubation period ranging from 2 to 8 days and possibly as long as 17 days. Current data for A(H7N9) infection indicate an incubation period ranging from 2 to 8 days, with an average of five days.1 WHO currently recommends that an incubation period of 7 days be used for field investigations and the monitoring of patient contacts.
Initial symptoms include high fever, usually with a temperature higher than 38°C, and other influenza-like symptoms (cough or sore throat). Diarrhea, vomiting, abdominal pain, chest pain, and bleeding from the nose and gums have also been reported as early symptoms in some patients.
One feature seen in many patients is the development of lower respiratory tract early in the illness. Respiratory distress, a hoarse voice, and a crackling sound when inhaling are commonly seen. Sputum production is variable and sometimes bloody.2 Complications of A(H5N1) and A(H7N9) infection include hypoxemia, multiple organ dysfunction, and secondary bacterial and fungal infections.3
Antiviral treatment
Evidence suggests that some antiviral drugs, notably oseltamivir, can reduce the duration of viral replication and improve prospects of survival.
In suspected cases, oseltamivir should be prescribed as soon as possible (ideally, within 48 hours following symptom onset) to maximize its therapeutic benefits. However, given the significant mortality currently associated with A(H5N1) and A(H7N9) infection and evidence of prolonged viral replication in this disease, administration of the drug should also be considered in patients presenting later in the course of illness. The use of corticosteroids is not recommended.
In cases of severe infection with the A(H5N1) or A(H7N9) virus, clinicians may need to consider increasing the recommended daily dose or/and the duration of treatment.
In severely ill A(H5N1) or A(H7N9) patients or in patients with severe gastrointestinal symptoms, drug absorption may be impaired. This possibility should be considered when managing these patients.4 Moreover, most A(H5N1) and A(H7N9) viruses are predicated to be resistant to adamantine antiviral drugs, which are therefore not recommended for use.
Risk factors for human infection
The primary risk factor for human infection appears to be direct or indirect exposure to infected live or dead poultry or contaminated environments, such as live bird markets. Controlling circulation of the A(H5N1) and A(H7N9) viruses in poultry is essential to reducing the risk of human infection. Given the persistence of the A(H5N1) and A(H7N9) viruses in some poultry populations, control will require long-term commitments from countries and strong coordination between animal and public health authorities.
There is no evidence to suggest that the A(H5N1)and A(H7N9) viruses can be transmitted to humans through properly prepared poultry or eggs. A few A(H5N1) human cases have been linked to consumption of dishes made of raw, contaminated poultry blood. However, slaughter, defeathering, handling carcasses of infected poultry, and preparing poultry for consumption, especially in household settings, are likely to be risk factors.
Human pandemic potential
Influenza pandemics (outbreaks that affect a large proportion of the world due to a novel virus) are unpredictable but recurring events that can have health, economic and social consequences worldwide. An influenza pandemic occurs when key factors converge: an influenza virus emerges with the ability to cause sustained human-to-human transmission, and the human population has little to no immunity against the virus. With the growth of global trade and travel, a localized epidemic can transform into a pandemic rapidly, with little time to prepare a public health response.
The A(H5N1) and A(H7N9) AI viruses remain two of the influenza viruses with pandemic potential, because they continue to circulate widely in some poultry populations, most humans likely have no immunity to them, and they can cause severe disease and death in humans.
However, whether the influenza A(H7N9) virus could actually cause a pandemic is unknown. Experience has shown that some animal influenza viruses that have been found to occasionally infect people have not gone on to cause a pandemic while others have done so. Surveillance and the investigations now underway will provide some of the information needed to make this determination.
In addition to A(H5N1) and A(H7N9), other animal influenza virus subtypes reported to have infected people include avian H9, and swine H1 and H3 viruses. H2 viruses may also pose a pandemic threat. Therefore, pandemic planning should consider risks of emergence of a variety of influenza subtypes from a variety of sources.
WHO response
WHO, in its capacity for providing leadership on global health matters, is monitoring avian influenza very closely, developing and adjusting appropriate interventions in collaboration with its partners. Such partners include animal health agencies and national veterinary authorities responsible for the control and prevention of animal diseases, including influenza.
Specifically, WHO, the World Organisation for Animal Health (OIE), and the Food and Agriculture Organization (FAO) collaborate through a variety of mechanisms to track and assess the risk from animal influenza viruses of public health concern, and to address these risks at the human animal interface wherever in the world they might occur. In short, WHO is monitoring the situation as it evolves, and as more information becomes available, will revise its guidance and actions accordingly.
Info from Wikepedia
Avian influenza — known informally as avian flu or bird flu — refers to "influenza caused by viruses adapted to birds."[1][2][3][4][5][6][7] The version with the greatest concern is highly pathogenic avian influenza (HPAI).
"Bird flu" is a phrase similar to "swine flu," "dog flu," "horse flu," or "human flu" in that it refers to an illness caused by any of many different strains of influenza viruses that have adapted to a specific host. All known viruses that cause influenza in birds belong to the species influenza A virus. All subtypes (but not all strains of all subtypes) of influenza A virus are adapted to birds, which is why for many purposes avian flu virus is the influenza A virus. (Note, however, that the "A" does not stand for "avian").
Adaptation is not exclusive. Being adapted toward a particular species does not preclude adaptations, or partial adaptations, toward infecting different species. In this way, strains of influenza viruses are adapted to multiple species, though may be preferential toward a particular host. For example, viruses responsible for influenza pandemics are adapted to both humans and birds. Recent influenza research into the genes of the Spanish flu virus shows it to have genes adapted to both birds and humans, with more of its genes from birds than less deadly later pandemic strains.
While its most highly pathogenic strain (H5N1) had been spreading throughout Asia since 2003, avian influenza reached Europe in 2005, and the Middle East, as well as Africa, the following year.[8] On January 22, 2012, China reported its second human death due to bird flu in a month following other fatalities in Vietnam and Cambodia.[9] Companion birds in captivity and parrots are highly unlikely to contract the virus, and there has been no report of a companion bird with avian influenza since 2003. Pigeons do not contract or spread the virus.[10][11][12] 84% of affected bird populations are composed of chicken and farm birds, while the 15% is madeup of wild birds according to capture-and-release operations in the 2000s, during the SARs pandemic. The first deadly Canadian case was confirmed on January 3, 2014.[13]
Genetics[edit]
Genetic factors in distinguishing between "human flu viruses" and "avian flu viruses" include:
PB2: (RNA polymerase): Amino acid (or residue) position 627 in the PB2 protein encoded by the PB2 RNA gene. Until H5N1, all known avian influenza viruses had a Glu at position 627, while all human influenza viruses had a Lys.[citation needed]
HA: (hemagglutinin): Avian influenza HA viruses bind alpha 2-3 sialic acid receptors, while human influenza HA viruses bind alpha 2-6 sialic acid receptors. Swine influenza viruses have the ability to bind both types of sialic acid receptors. Hemagglutinin is the major antigen of the virus against which neutralizing antibodies are produced, and influenza virus epidemics are associated with changes in its antigenic structure. This was originally derived from pigs, and should technically be referred to as "pig flu" [14]
Subtypes[edit]
There are many subtypes of avian influenza viruses, but only some strains of four subtypes have been highly pathogenic in humans. These are types H5N1, H7N3, H7N7, H7N9, and H9N2.[15] At least one person, an elderly woman in Jiangxi Province, China, died of pneumonia in December 2013 from the H10N8 strain, the first human fatality confirmed to be caused by that strain.[16]
Contraction/spreading of avian influenza[edit]
Most human contractions of the avian flu are a result of either handling dead infected birds or from contact with infected fluids. While most wild birds mainly have only a mild form of the H5N1 strain, once domesticated birds such as chickens or turkeys are infected, it could become much more deadly because the birds are often within close contact of one another. There is currently a large threat of this in Asia with infected poultry due to low hygiene conditions and close quarters. Although it is easy for humans to become infected from birds, it's much more difficult to do so from human to human without close and lasting contact.
Spreading of H5N1 from Asia to Europe is much more likely caused by both legal and illegal poultry trades than dispersing through wild bird migrations, being that in recent studies, there were no secondary rises in infection in Asia when wild birds migrate south again from their breeding grounds. Instead, the infection patterns followed transportation such as railroads, roads, and country borders, suggesting poultry trade as being much more likely. While there have been strains of avian flu to exist in the United States, such as Texas in 2004, they have been extinguished and have not been known to infect humans.
Examples of avian influenza A virus strains:[17]
HA subtype
designation
NA subtype
designation
Avian influenza A viruses
H1
N1
A/duck/Alberta/35/76(H1N1)
H1
N8
A/duck/Alberta/97/77(H1N8)
H2
N9
A/duck/Germany/1/72(H2N9)
H3
N8
A/duck/Ukraine/63(H3N8)
H3
N8
A/duck/England/62(H3N8)
H3
N2
A/turkey/England/69(H3N2)
H4
N6
A/duck/Czechoslovakia/56(H4N6)
H4
N3
A/duck/Alberta/300/77(H4N3)
H5
N3
A/tern/South Africa/300/77(H4N3)
H5
N4
A/Ethiopia/300/77(H6N6)
H5
N9
A/turkey/Ontario/7732/66(H5N9)
H5
N1
A/chick/Scotland/59(H5N1)
H6
N2
A/turkey/Massachusetts/3740/65(H6N2)
H6
N8
A/turkey/Canada/63(H6N8)
H6
N5
A/shearwater/Australia/72(H6N5)
H6
N6
A/jyotichinara/Ehiopia/73(H6N6)
H6
N1
A/duck/Germany/1868/68(H6N1)
H7
N7
A/fowl plague virus/Dutch/27(H7N7)
H7
N1
A/chick/Brescia/1902(H7N1)
H7
N9
A/chick/China/2013(H7N9)
H7
N3
A/turkey/England/639H7N3)
H7
N1
A/fowl plague virus/Rostock/34(H7N1)
H8
N4
A/turkey/Ontario/6118/68(H8N4)
H9
N2
A/turkey/Wisconsin/1/66(H9N2)
H9
N6
A/duck/Hong Kong/147/77(H9N6)
H9
N6
A/duck/Hong Kong/147/77(H9N6)
H9
N8
A/manishsurpur/Malawi/149/77(H9N8)
H9
N7
A/turkey/Scotland/70(H9N7)
H10
N8
A/quail/Italy/1117/65(H10N8)
H11
N6
A/duck/England/56(H11N6)
H11
N9
A/duck/Memphis/546/74(H11N9)
H12
N5
A/duck/Alberta/60/76/(H12N5)
H13
N6
A/gull/Maryland/704/77(H13N6)
H14
N4
A/duck/Gurjev/263/83(H14N4)
H15
N9
A/shearwater/Australia/2576/83(H15N9)
Influenza pandemic[edit]
Further information: Influenza pandemic
Pandemic flu viruses have some avian flu virus genes and usually some human flu virus genes. Both the H2N2 and H3N2 pandemic strains contained genes from avian influenza viruses. The new subtypes arose in pigs coinfected with avian and human viruses, and were soon transferred to humans. Swine were considered the original "intermediate host" for influenza, because they supported reassortment of divergent subtypes. However, other hosts appear capable of similar coinfection (e.g., many poultry species), and direct transmission of avian viruses to humans is possible.[18] The Spanish flu virus strain may have been transmitted directly from birds to humans.[19]
In spite of their pandemic connection, avian influenza viruses are noninfectious for most species. When they are infectious, they are usually asymptomatic, so the carrier does not have any disease from it. Thus, while infected with an avian flu virus, the animal does not have a "flu". Typically, when illness (called "flu") from an avian flu virus does occur, it is the result of an avian flu virus strain adapted to one species spreading to another species (usually from one bird species to another bird species). So far as is known, the most common result of this is an illness so minor as to be not worth noticing (and thus little studied). But with the domestication of chickens and turkeys, humans have created species subtypes (domesticated poultry) that can catch an avian flu virus adapted to waterfowl and have it rapidly mutate into a form that kills over 90% of an entire flock in days, can spread to other flocks and kill 90% of them, and can only be stopped by killing every domestic bird in the area. Until H5N1 infected humans in the 1990s, this was the only reason avian flu was considered important. Since then, avian flu viruses have been intensively studied; resulting in changes in what is believed about flu pandemics, changes in poultry farming, changes in flu vaccination research, and changes in flu pandemic planning.
Influenza A/H5N1 has evolved into a flu virus strain that infects more species than any previously known strain, is deadlier than any previously known strain, and continues to evolve, becoming both more widespread and more deadly. This caused Robert G. Webster, a leading expert on avian flu, to publish an article titled "The world is teetering on the edge of a pandemic that could kill a large fraction of the human population" in American Scientist. He called for adequate resources to fight what he sees as a major world threat to possibly billions of lives.[20]
Vaccines for poultry have been formulated against several of the avian H5N1 influenza varieties. Vaccination of poultry against the ongoing H5N1 epizootic is widespread in certain countries. Some vaccines also exist for use in humans, and others are in testing, but none have been made available to civilian populations, nor are produced in quantities sufficient to protect more than a tiny fraction of the Earth's population in the event of an H5N1 pandemic outbreak. The World Health Organization has compiled a list of known clinical trials of pandemic influenza prototype vaccines, including those against H5N1.
H5N1[edit]
H5N1
• subtype H5N1
• in 2004
• in 2005
• in 2006
• in 2007
• Pandemic
• Vaccine
Further information: Influenza A virus subtype H5N1 and Transmission and infection of H5N1
The highly pathogenic influenza A virus subtype H5N1 is an emerging avian influenza virus that has been causing global concern as a potential pandemic threat. It is often referred to simply as "bird flu" or "avian influenza", even though it is only one subtype of avian influenza-causing virus.
H5N1 has killed millions of poultry in a growing number of countries throughout Asia, Europe, and Africa. Health experts are concerned that the coexistence of human flu viruses and avian flu viruses (especially H5N1) will provide an opportunity for genetic material to be exchanged between species-specific viruses, possibly creating a new virulent influenza strain that is easily transmissible and lethal to humans. The mortality rate for humans with H5N1 is 60%.
Since the first H5N1 outbreak occurred in 1987, there has been an increasing number of HPAI H5N1 bird-to-human transmissions, leading to clinically severe and fatal human infections. Because a significant species barrier exists between birds and humans, though, the virus does not easily cross over to humans, though some cases of infection are being researched to discern whether human to human transmission is occurring.[18] More research is necessary to understand the pathogenesis and epidemiology of the H5N1 virus in humans. Exposure routes and other disease transmission characteristics, such as genetic and immunological factors that may increase the likelihood of infection, are not clearly understood.[21]
On January 18, 2009, a 27-year-old woman from eastern China died of bird flu, Chinese authorities said, making her the second person to die from the deadly virus at that time. Two tests on the woman were positive for H5N1 avian influenza, said the ministry, which did not say how she might have contracted the virus.[22]
Although millions of birds have become infected with the virus since its discovery, 359 humans have died from the H5N1 in twelve countries according to WHO data as of August 10, 2012.[23]
The avian flu claimed at least 300 humans in Azerbaijan, Cambodia, China, Egypt, Indonesia, Iraq, Laos, Nigeria, Pakistan, Thailand, Turkey, and Vietnam. Epidemiologists are afraid the next time such a virus mutates, it could pass from human to human; however, the current A/H5N1 virus does not transmit easily from human to human. If this form of transmission occurs, another pandemic could result. Thus, disease-control centers around the world are making avian flu a top priority. These organizations encourage poultry-related operations to develop a preemptive plan to prevent the spread of H5N1 and its potentially pandemic strains. The recommended plans center on providing protective clothing for workers and isolating flocks to prevent the spread of the virus.[24]
The Thailand outbreak of avian flu caused massive economic losses, especially among poultry workers. Infected birds were culled and slaughtered. The public lost confidence with the poultry products, thus decreasing the consumption of chicken products. This also elicited a ban from importing countries. There were, however, factors which aggravated the spread of the virus, including bird migration, cool temperature (increases virus survival) and several festivals at that time.[25]
H7N9[edit]
Further information: Influenza A virus subtype H7N9
Influenza A virus subtype H7N9 is a novel avian influenza virus first reported to have infected humans in 2013 in China.[26] Most of the reported cases of human infection have resulted in severe respiratory illness.[27] In the month following the report of the first case, more than 100 people had been infected, an unusually high rate for a new infection; a fifth of those patients had died, a fifth had recovered, and the rest remained critically ill.[28] The World Health Organization (WHO) has identified H7N9 as "...an unusually dangerous virus for humans."[29] As of June 30, 133 cases have been reported, resulting in the deaths of 43.
Research regarding background and transmission is ongoing.[30] It has been established that many of the human cases of H7N9 appear to have a link to live bird markets.[31] As of July, there has been no evidence of sustained human-to-human transmission, however a study group headed by one of the world’s leading experts on avian flu reported that several instances of human-to-human infection are suspected.[32] It has been reported that H7N9 virus does not kill poultry, which will make surveillance much more difficult. Researchers have commented on the unusual prevalence of older males among H7N9-infected patients.[33] While several environmental, behavioral, and biological explanations for this pattern have been proposed,[34] as yet, the reason is unknown.[35] Currently no vaccine exists, but the use of influenza antiviral drugs known as neuraminidase inhibitors in cases of early infection may be effective.[36]
The number of cases detected after April fell abruptly. The decrease in the number of new human H7N9 cases may have resulted from containment measures taken by Chinese authorities, including closing live bird markets, or from a change in seasons, or possibly a combination of both factors. Studies indicate that avian influenza viruses have a seasonal pattern, thus it is thought that infections may pick up again when the weather turns cooler in China.[37]
In domestic animals[edit]
Several domestic species have been infected with and shown symptoms of H5N1 viral infection, including cats, dogs, ferrets, pigs, and birds.[38]
Birds[edit]
Attempts are made in the United States to minimize the presence of HPAI in poultry thorough routine surveillance of poultry flocks in commercial poultry operations. Detection of a HPAI virus may result in immediate culling of the flock. Less pathogenic viruses are controlled by vaccination, which is done primarily in turkey flocks (ATCvet codes: QI01AA23 for the inactivated fowl vaccine, QI01CL01 for the inactivated turkey combination vaccine).[39]
Seals[edit]
A recent strain of the virus is able to infect the lungs of seals.[40]
Cats[edit]
Avian influenza in cats can show a variety of symptoms and usually lead to death. Cats are able to get infected by either consuming an infected bird or by passing it to other cats.
Influenza Prevention[edit]
People who have fewer chances to contact with birds do not belong to the high-risk group of HPAI. If people take precautions correctly and be more careful, the chance of infection will be very low, even among farmers.
In the aware of bird flu pandemic, people should have careful thought to adopt suitable Infection Control Procedures. Try to avoid flu infection in any situation will be necessary. Protecting eyes, nose, mouth and hands from virus particles will be a major priority because these are the most common passageways for a flu virus to transfer into the body.[41] Bird flu virus particles may also be transferred through clothing or even shoes. The final step is people should always have sanitized hands in order to further reduce the chances of cross-contamination. Any unprotected clothing or footwear should be disinfected. Avoid contact with poultry, and maintaining good personal hygiene is very important, too. Someone who has normal flu should be more careful in avoiding contact with fowl because the epidemic situation will become even more serious if the receptor protein of normal flu and the genes of Avian Flu combine with each other.[41]
from cdc
Types of Influenza Viruses
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There are three types of influenza viruses: A, B and C. Human influenza A and B viruses cause seasonal epidemics of disease almost every winter in the United States. The emergence of a new and very different influenza virus to infect people can cause an influenza pandemic. Influenza type C infections cause a mild respiratory illness and are not thought to cause epidemics.
Influenza A viruses are divided into subtypes based on two proteins on the surface of the virus: the hemagglutinin (H) and the neuraminidase (N). There are 18 different hemagglutinin subtypes and 11 different neuraminidase subtypes. (H1 through H18 and N1 through N11 respectively.)
Influenza A viruses can be further broken down into different strains. Current subtypes of influenza A viruses found in people are influenza A (H1N1) and influenza A (H3N2) viruses. In the spring of 2009, a new influenza A (H1N1) virus (CDC 2009 H1N1 Flu website) emerged to cause illness in people. This virus was very different from the human influenza A (H1N1) viruses circulating at that time. The new virus caused the first influenza pandemic in more than 40 years. That virus (often called “2009 H1N1”) has now replaced the H1N1 virus that was previously circulating in humans.
Influenza B viruses are not divided into subtypes, but can be further broken down into lineages and strains. Currently circulating influenza B viruses belong to one of two lineages: B/Yamagata and B/Victoria.
CDC follows an internationally accepted naming convention for influenza viruses. This convention was accepted by WHO in 1979 and published in February 1980 in the Bulletin of the World Health Organization, 58(4):585-591 (1980) (see A revision of the system of nomenclature for influenza viruses: a WHO Memorandum[854 KB, 7 pages]). The approach uses the following components:
• The antigenic type (e.g., A, B, C)
• The host of origin (e.g., swine, equine, chicken, etc. For human-origin viruses, no host of origin designation is given.)
• Geographical origin (e.g., Denver, Taiwan, etc.)
• Strain number (e.g., 15, 7, etc.)
• Year of isolation (e.g., 57, 2009, etc.)
• For influenza A viruses, the hemagglutinin and neuraminidase antigen description in parentheses (e.g., (H1N1), (H5N1)
For example:
• A/duck/Alberta/35/76 (H1N1) for a virus from duck origin
• A/Perth/16/2009 (H3N2) for a virus from human origin
Influenza A (H1N1), A (H3N2), and one or two influenza B viruses (depending on the vaccine) are included in each year’s influenza vaccine. Getting a flu vaccine can protect against flu viruses that are the same or related to the viruses in the vaccine. Information about this season’s vaccine can be found at Preventing Seasonal Flu with Vaccination. The seasonal flu vaccine does not protect against influenza C viruses. In addition, flu vaccines will NOT protect against infection and illness caused by other viruses that also can cause influenza-like symptoms. There are many other non-flu viruses that can result in influenza-like illness (ILI) that spread during flu season.
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