Logan Reed
Swine influenza, also known as swine flu, is a respiratory disease that regularly causes outbreaks in pigs. While it rarely results in fatalities, it can cause high levels of illness in pig herds. Swine flu viruses can spread among pigs when an infected pig coughs or sneezes, similar to how the flu spreads among humans. Various strains of the influenza A virus have been isolated in pigs, including H1N1, H1N2, and H3N2. Fortunately, vaccines are available to help prevent swine flu in pigs, and these vaccines can also provide cross-protection against different strains and subtypes of the virus. However, the effectiveness of these vaccines may be limited due to the constant evolution of the virus, and the need to closely match the vaccine virus with the epidemic virus.
| Characteristics | Values |
|---|---|
| Are vaccines available for Influenza A H3N2 Swine? | Yes, there are specific swine influenza vaccines available for pigs. |
| Effectiveness of vaccines | Flu vaccines for pigs may not be 100% effective and may not protect against all viruses spreading in pigs. |
| Types of vaccines | Bivalent SIV vaccines, NS1-Truncated Modified Live-Virus Vaccine, MLV |
| Countries with available vaccines | The US |
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What You'll Learn
There are specific vaccines for swine flu
Swine influenza (SIV) is a respiratory disease that causes regular outbreaks in pigs. While swine flu rarely results in deaths in pigs, it can cause high levels of illness in pig herds. Swine flu viruses can spread among pigs through close contact and contaminated objects, but mainly through droplets in the air when infected pigs cough or sneeze.
Swine flu viruses can also infect humans. When swine flu infects humans, it is called a "variant virus". For example, the influenza A (H3N2) variant virus, or H3N2v, was first identified in pigs in the United States in 2010 and has since infected humans. The spread of swine flu from infected pigs to humans is thought to occur in the same way as seasonal influenza spreads between humans. Therefore, it is recommended to wear gloves and a mask when near pigs that are known or suspected to be infected with influenza.
There are specific vaccines available for swine flu. Flu vaccines for pigs can help reduce the risk of pigs getting the flu, but they may not be 100% effective. The effectiveness of influenza vaccines depends on the closeness of the match between the vaccine virus and the epidemic virus. In some cases, flu vaccines used in pigs may not protect against the virus spreading in pigs if the vaccine virus does not match the influenza A virus circulating in the pigs.
Currently, there are several bivalent SIV vaccines commercially available in the United States. These vaccines are based on killed viruses containing both H1N1 and H3N2 subtypes. However, due to genetic and antigenic heterogeneities within each subtype of SIV, vaccine effectiveness may be reduced. Additionally, an NS1-truncated modified live-virus vaccine has been studied for its potential use in differentiating infected from vaccinated animals. This vaccine, based on an H3N2 SIV with a deleted NS1 gene, has shown complete protection against challenge with a homosubtypic H3N2 virus and partial protection against a heterosubtypic H1N1 virus in pigs.
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Swine flu vaccines may not be 100% effective
Swine influenza (swine flu) is a respiratory disease that regularly causes outbreaks in pigs. It is caused by type A influenza viruses, including H1N1, H1N2, and H3N2. While there are specific swine influenza vaccines available for pigs, they may not be 100% effective in preventing the disease.
The effectiveness of influenza vaccines depends on how well the vaccine virus matches the epidemic virus. However, the constantly changing nature of swine influenza viruses poses a challenge for vaccine development. Pigs can be infected by avian influenza, human influenza, and swine influenza viruses. When these viruses infect pigs, they can reassort and create new subtypes through genetic exchange. This results in the emergence of novel influenza subtypes, such as the H3N2 virus, which was introduced to pigs from humans.
The changing nature of swine influenza viruses can lead to situations where the vaccine virus does not match the circulating influenza A virus in pig populations. In such cases, the vaccine may not provide effective protection against the virus. For example, a study found that out of 97 recent H3N2 isolates, only 41 showed strong serologic cross-reactions with antiserum to three commercial SIV vaccines. This indicates that the current commercial vaccines may not protect against a majority of H3N2 viruses.
Furthermore, there is a risk of vaccine-induced antibodies exacerbating respiratory symptoms when pigs are infected with a different flu strain. For instance, a 2013 study reported that piglets vaccinated against H1N2 flu developed severe pneumonia and lung damage when subsequently infected with the 2009 H1N1 virus. The cross-reactive antibodies triggered by the vaccine were found to have worsened respiratory problems by aiding the virus in fusing with cell membranes.
While swine flu vaccines can help reduce the risk of pigs contracting the flu, they may not offer complete protection against all circulating strains. Therefore, it is essential to continuously monitor the effectiveness of vaccines against emerging swine influenza subtypes and work towards developing more robust and effective vaccines.
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H3N2 is a prevalent strain of flu
H3N2 is a subtype of the influenza A virus (IAV) and is known to infect both humans and pigs (swine). In pigs, H3N2 is considered endemic in China and has also been detected in Vietnam. The circulation of H3N2 in pigs poses a risk of new variant strains emerging as pigs can act as intermediate hosts for the virus. This allows for the exchange of genetic material between different subtypes of the virus, leading to the emergence of new variants that can be transmitted to humans.
In the United States, H3N2 swine flu viruses began circulating among pig populations in 1998, and these viruses have since evolved and changed. While swine flu typically affects pigs, with rare cases of human infection, it is still a significant concern for the industry. Vaccines for swine flu are available and used on swine farms, but they may not always be effective due to the constant evolution of the virus.
For humans, seasonal influenza vaccines are typically formulated to include strains of the H3N2 subtype, as it is one of the prevalent subtypes contributing to seasonal flu outbreaks. However, the effectiveness of these vaccines can vary, and the World Health Organization (WHO) continuously monitors and updates the recommended strains for the flu vaccine to improve its protective efficacy.
The prevalence and impact of the H3N2 strain highlight the ongoing challenge of managing influenza and the need for continuous surveillance, research, and vaccine development to stay ahead of evolving flu strains.
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H3N2 vaccines are included in biannual reformulation
Seasonal influenza vaccines are formulated twice a year to include HA protein, or attenuated influenza virus, of the three influenza strains representative of the circulating strains in the northern or southern hemisphere. Routinely, formulations contain two human influenza A subtypes (H3N2 and H1N1) and one of the two influenza B lineages (Yamagata or Victoria). Seasonal influenza is an annually recurring outbreak of flu that occurs during the cold half of the year in each hemisphere. Annually, about 3 to 5 million cases of severe illness and 290,000 to 650,000 deaths from seasonal flu occur worldwide. A/H3N2 is one of the prevalent subtypes of flu that contributes to seasonal flu outbreaks, and a strain of A/H3N2 is usually included in the biannual reformulation of the flu vaccine.
The Hong Kong Flu was a flu pandemic caused by a strain of H3N2 descended from H2N2 by antigenic shift, in which genes from multiple subtypes reassorted to form a new virus. This pandemic of 1968 and 1969 killed an estimated one million people worldwide. The pandemic infected an estimated 500,000 Hong Kong residents, 15% of the population, with a low death rate. In the United States, about 100,000 people died. Both the H2N2 and H3N2 pandemic flu 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, as they supported the 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.
H3N2 is one of the three main influenza A virus subtypes that have been isolated in pigs in the United States, along with H1N1 and H1N2. H3N2 influenza viruses did not begin circulating among pigs in the United States until about 1998. The H3N2 viruses initially were introduced into the pig population from humans. However, since then, the H3N2 viruses circulating in pigs have changed and are now very different from the seasonal H3N2 viruses that circulate in humans. Present vaccination strategies for swine influenza virus (SIV) control and prevention in swine farms typically include the use of one of several bivalent SIV vaccines commercially available in the United States. Of the 97 recent H3N2 isolates examined, only 41 had strong serologic cross-reactions with antiserum to three commercial SIV vaccines.
Although we have made significant advances in understanding influenza, current vaccines updated annually to protect against anticipated seasonal virus strains are at best 60% effective and often less so. Antigenic drift resulting from mutations in critical proteins of the influenza virus allows the virus to evade the strain-specific immunity elicited by current vaccines. Moreover, over the past hundred years, antigenic shifts or major changes in influenza strains have resulted in pandemics. Thus, a better approach to influenza vaccination is needed. During the last 10 years, newer technologies have emerged, stimulating scientists to answer old questions in new, more precise ways and to ask novel questions that could not previously be addressed. Scientific advances that directly benefit vaccinology include monoclonal antibody isolation and identification, structural biology, protein engineering, and antigen delivery amenable to platform manufacturing approaches.
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H3N2 is endemic in pigs in China
H3N2 is a subtype of the influenza A virus. It is one of the prevalent subtypes of flu that contribute to seasonal flu outbreaks. H3N2 is endemic in pigs in China and has also been detected in pigs in Vietnam.
Swine influenza is a respiratory disease that regularly causes outbreaks in pigs. It is caused by type A influenza viruses. These viruses can spread among pigs similarly to how human flu viruses spread among people—through droplets containing flu A virus that spread through the air when infected pigs cough or sneeze. They can also spread among pigs through close contact and possibly through contaminated objects.
Pigs are unusual because they can be infected with influenza strains that usually infect three different species: pigs, birds, and humans. Within pigs, influenza viruses may exchange genes and produce novel strains. This is known as genetic reassortment, and it can lead to the emergence of new variant strains that can pass easily among humans.
Vaccines for swine influenza are available and can help reduce the risk of pigs getting the flu. However, they may not be 100% effective as the effectiveness depends on the closeness of the match between the vaccine virus and the epidemic virus. In a study of 97 recent H3N2 isolates, only 41 had strong serologic cross-reactions with antiserum to three commercial SIV vaccines. This suggests that current commercial vaccines might not effectively protect pigs from infection with most H3N2 viruses.
To address this challenge, researchers have developed modified live-virus vaccines, such as the TX98 NS1▴126 MLV vaccine. This vaccine has been shown to provide complete protection against challenge with a homosubtypic H3N2 virus and partial protection against a heterosubtypic H1N1 virus.
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Frequently asked questions
Yes, there are specific swine influenza vaccines available for pigs.
Flu vaccines for pigs can help reduce the risk of pigs getting the flu but may not be 100% effective. Sometimes, flu vaccines used in pigs may not protect against the virus or viruses that are spreading in pigs, because the vaccine virus may not match the influenza A virus that is circulating in the pigs.
Swine flu viruses spread among pigs in the same way that human flu viruses spread among people. That is mainly through droplets containing flu A virus that spread through the air when infected pigs cough or sneeze.
