On January 29, Spanish authorities notified the European Center for Disease Prevention and Control (ECDC) of a possible case of COVID-19 infection. Swine flu A worker at a pig farm in Lleida. The patient developed symptoms in late November and was diagnosed with bronchitis but showed no signs of pneumonia.
According to the ECDC (in its weekly bulletin for the week of January 28 to February 3), some first laboratory analyzes in December showed that this was influenza A; subsequently, the Catalonia Regional Reference Laboratory After more detailed examination, it was determined that this was the H1N1 swine influenza virus. ECDC also said that the patient has fully recovered and no new cases of infection have been detected among his family or farm colleagues.
Since 2011, 73 cases of influenza A (H1N1) swine influenza virus infection have been reported globally. Two of them are in Spain (China has the highest incidence rate, with 42 reported cases). The ECDC notes that swine influenza viruses are widespread in pigs and that direct human contact with these animals is the most common risk factor for infection. Therefore, sporadic infections are to be expected, especially when people have direct unprotected contact with infected animals. It is worth mentioning that swine flu is spread through the air (by inhaling contaminated aerosols from animals), not through food, so there is no risk of transmission through the consumption of pork products.
Journalist Iole Ferrara Romeo interviewed Aitor Nogales, virologist and researcher at the Animal Health Research Center (CISA) of the National Institute of Agricultural and Food Research and Technology (INIA-CSIC), on this topic. His career spans more than 10 years and he is an expert in influenza virus research.
The ECDC said sporadic cases of swine flu could occur in humans, so the contagion in Lleida did not appear to be a cause for concern. Has the possibility of human-to-human transmission of this virus been ruled out for the time being?
It is not uncommon for swine flu viruses to infect humans. Many of these cases were detected, while others – because they were asymptomatic or because biosurveillance was not in place – were not detected, but this is not surprising. Generally, this infection is asymptomatic, or causes the same symptoms as the common flu, and usually does not spread from person to person, or spreads very inefficiently.
The 2009 influenza pandemic was caused by a variant of the H1N1 swine flu virus. What happened then? Why is it so different from the current situation?
The virus that caused the 2009 influenza pandemic (the last flu pandemic to date) was complex because it contained segments of swine, avian, and human flu. In the current case, on the other hand, sequencing of the virus isolated from the patient found that all genes matched the pig variant currently circulating.
In 2009, tracking revealed that the virus was transmitted from pigs to humans. But this is a virus that came from afar and, as they say, has been brewing for years.
This infection is asymptomatic or causes the same symptoms as the common flu and is not usually spread from person to person.
Why in pigs?
Due to their biological characteristics, pigs are susceptible to infection by different types of influenza viruses, human influenza viruses, avian influenza viruses, etc. Therefore, the risk is that they become intermediate hosts, with which different viruses may overlap at the same time, which favors the emergence of new variants. Ultimately, they could also lead to the formation of a new virus with pandemic potential, as happened in 2009.
How do different types of new viruses arise within organisms?
The genomes of influenza viruses are defined as segmented, that is, they are composed of multiple molecules. When animals are infected with two different influenza viruses, genome segments from the two viruses can mix, creating a virus with new characteristics. For example, this system may provide the virus with some advantages in terms of replication and infectivity. It’s common in influenza, but it also occurs in other viruses and is one of the ways they evolve.
Laboratory trials are needed to verify the effectiveness of seasonal human influenza vaccines against swine viruses.However, assuming it provides partial protection
Can human flu vaccines protect against swine flu viruses?
It really needs to be evaluated. Seasonal human influenza vaccines are reformulated annually, so laboratory trials must be conducted to verify their effectiveness against swine viruses. However, it is assumed that it provides partial protection.
In fact, getting a seasonal flu vaccine is one of the recommendations for people who work with pigs and poultry. This is for two reasons, the first is that it protects them, even partially; The second is to prevent staff from transmitting viruses other than swine viruses to pigs, which may bring the risk of new variants emerging. Regarding the case in Lleida, at the moment we don’t know, or I don’t know, whether the worker was vaccinated.
Generally, swine flu virus infection is asymptomatic or causes the same symptoms as the common flu. Although it does not cause serious illness, why should we try to prevent these infections from occurring?
True, severe symptoms are rare, but the more the virus spreads, the higher the incidence of severe cases. For example, if we consider seasonal influenza in humans, it is estimated that nearly half a million people die every year because of the widespread circulation of the virus. We are also seeing this with the covid-19 pandemic. If the virus spreads on a large scale, even if the mortality rate is low, the death toll will eventually be high. Therefore, workers must be protected even if the infection does not cause serious illness; we must prevent the virus from starting to spread. This is a public health issue.
What measures can be taken to protect pig farm workers?
In addition to seasonal influenza vaccination, farm biosecurity measures such as disinfection, use of personal protective equipment (PPE), hand washing, etc. must also be observed. All of these measures are extremely important because they protect against not only the flu, but many other pathogens as well. They provide protection in both directions: from animals to humans and from humans to animals.
Workers must be protected even if the infection does not cause serious illness; we must prevent the virus from starting to spread
Is there a risk that what happened in 2009 could happen again? How can we avoid it?
In order to detect the virus in time, epidemiological surveillance measures must be implemented, that is, knowing which virus variants are circulating and where. As for influenza, seasonal viruses are often isolated and sequenced extensively, which is also a way to predict what will spread next season.
The ECDC itself states that zoonotic influenza viruses isolated from patients must be sequenced and thoroughly characterized, and that these data must be shared with the National Influenza Reference Laboratory and World Health Organization (WHO) Collaborating Centers.
The World Health Organization says the question is not if there will be another flu pandemic, but when the next one will happen and where it will come from. Influenza pandemics have existed throughout history, and there is no reason to think that now—in a more globalized world than before—what has been happening for centuries will stop happening.
fountain: China Shipbuilding Industry Corporation
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Article by: Iole Ferrara Romeo / Content from CSIC-BBVA Foundation for Science Communication Grant Program, 2022 Conference Call