We don’t leave one and we can get into another. In recent days, the Democratic Republic of the Congo has been devastated by an unknown disease that already has left a trail of dead. On the other hand, in the United States, we have just found a swine infection due to avian flumore than enough reason to start worrying about the epidemic that is being experienced in the country.

From the other side of the world, the news is not very positive: Chinese scientists say that the world could be on the brink of another pandemic. The culprit? That bird flu virus that is mutating to better adapt to new organisms.

Nervousness. Let’s start with the case of the United States. In recent months, the country has faced a health crisis due to the H5N1 avian flu epidemic. There are several types of avian influenza type A depending on the combination of the hemagglutinin and neuraminidase proteins and what is known is that the H1N1 and H3N2 types can circulate among humans, according to the United States Center for Disease Control and Prevention.

The curious—and worrying—thing is that detected a pig infected by it H5N1. Avian flu has a specialized mechanism for infecting bird respiratory cells, making it difficult for the virus to infect human cells. Therefore, infections in humans usually occur only in people with close contact with infected animals. But introducing pigs into the equation could change that, warn from MacIntyre and Stone.

H2N2. Pigs can be infected with both avian and human viruses because the respiratory system of these animals is similar to ours. Therein lies the problem, since the virus could end up mixing its genetic material, adapting better to the human body through new variants that are potentially contagious for us. AND cases are already occurring.

As we say, good news is not coming from China either. George Fu Gao is one of the country’s most important virologists and directed the Chinese Center for Disease Control and Prevention for five years. Now, as we read in SCMPhas published an article with his team from the Chinese Academy of Sciences in which, by investigating a strain of the H2N2 virus, they have found that the virus has the ability to adapt to bind to avian and human receptors on the host’s cell surface.

Relative immunity. Experimenting on mice, guinea pigs and ferrets, the researchers found that the H2N2 strain could quickly adapt to mice, acquiring mutations adapted to mammals. From there, the strain jumped to guinea pigs and ferrets. Although the virus still showed a preference for avian receptors, the paper’s authors noted that a few decades ago it also preferred birds, but adapted to bind to human receptors.

Pandemic capacity. The key date is 1957, the year in which, originating in southern China, another strain of H2N2 spread rapidly among humans around the world. The “asian flu“caused more than a million deaths and was fleeting: at the end of the 60s, it disappeared from the human population because immunity was generated.

The problem is that, according to researchers, the time that has passed since that pandemic means that the current population lacks immunity against a possible future outbreak. The genetic difference of both the strain and the population also comes into play, which could increase the risk of a new avian flu pandemic among humans.

Human to human. Most cases of human-to-human transmission have occurred due to exposure to cows or poultry, and of the 900 cases of H5N1 infection reported to the World Health Organization between 2023 and 2024, approximately half had a fatal outcome. In none of the cases was it due to human-to-human transmission.

This is somewhat reassuring, but researchers believe the possibility still exists. The culprit could be H5N1, a strain that is not new, but is experiencing an “abrupt change” in viral shedding. This means that the expulsion of viral particles through exhalation is increasing, which could explain the recent increase in transmissions among livestock.

You have to be attentive. The Chinese team considers that, although the risk is still low, virus surveillance in animals must be strengthened and a public health risk assessment of new avian influenza viruses must be carried out. These are imperative measures for the control and prevention of emerging and re-emerging influenza pandemics and epidemics.

At the moment, there seems to be no reason to panic, but it is clear that the possibility of the virus adapting and acquiring the ability to be transmitted through viral excretion in a simpler way must be controlled.

Images | Muhammad Mahdi Karim, Brasilia Agency

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