Mexico: Bird flu under strict control

Bird flu is an infection caused by the A(H5N1) virus, which belongs to the Orthomyxoviridae family and affects all birds (domestic and wild).

it has been known for several years that this microorganism can be transmitted from birds to various mammals, including humans, foxes, and sea lions; however, as of March 25, 2024 , it was established that it is also capable of infecting cattle , as on that day, the first outbreak of avian influenza was reported among dairy cows in several US states .

But that's not all: on April 1 of this year, the first human case of bird flu was recorded in this country. The man was a worker on a dairy farm where the A(H5N1) virus was detected , transmitted by a sick cow. Although he only experienced eye irritation and not the respiratory symptoms typically associated with this virus (neither the infected cow nor any other sick individuals developed a serious infection). It should be added that since then, two more human cases have been identified in a neighboring country to the north.

According to the World HEALTH Organization, bird flu in humans can cause anything from a mild upper respiratory infection with fever and cough to pneumonia, acute respiratory distress syndrome, shock, and even death. This means the A(H5N1) virus can be highly or low-pathogenic.

Human cases of bird flu have been sporadic but very serious. To date, there have been no documented cases of human-to-human transmission of the disease. However, the A(H5N1) virus may undergo certain genetic changes that would allow for human-to-human transmission, thus creating a potentially dangerous scenario.

The A(H5N1) virus has already spread from birds to dairy cows and causes some minor health problems, including a mammary gland infection that affects MILK production . Because it may have undergone genetic changes and adapted to these animals, it was named bovine influenza A to distinguish it from the virus that infects birds.

"No human cases of avian influenza have yet been reported in Mexico. However, following the alert issued following the first case in the United States, the National Service of Health, Safety, and Quality of Agri-Food (SENASICA) has already launched a targeted search for the A(H5N1) virus on cattle ranches. In any case, people who work with or come into contact with dairy cows, such as veterinarians, must act with caution to avoid infection not only with the A(H5N1) virus but also with other viruses and bacteria that these animals may carry," says Mauricio Rodríguez Álvarez, a professor at UNAM's School of Medicine and a member of the University Plan for the Management of Antimicrobial Resistance, part of the University's Research Program on Epidemiological and Emerging Risks.

According to the university professor, the research hypothesis is that the microorganism that infected the dairy cows is the highly pathogenic A(H5N1) virus, which affects birds.

"This virus has likely undergone genetic changes that have allowed it to adapt to infect dairy cows, and it is now known that it can be transmitted from them to humans and other animals, causing a mild upper respiratory infection," he emphasizes.

People working on poultry farms are more susceptible to contracting bird flu because they are in direct and constant contact with the saliva, secretions, and feces of sick chickens and hens.

"And let's remember that many poultry farms house thousands of chickens and chicks, and quite a few of these animals may be carriers of the A(H5N1) virus. Furthermore, a person infected with this microorganism from a sick bird can develop a severe upper respiratory infection. The good news is that to date, there have been no recorded cases of human-to-human transmission of the virus," explains Rodriguez Alvarez.

This virus has already reached humans, that's an undeniable fact; now we need to be careful that it doesn't acquire the ability to transmit from person to person.

“The latter is crucial. We saw this with the SARS-CoV-2 virus, which causes"COVID-19 , which proved highly contagious among humans and ultimately caused a pandemic with catastrophic consequences. The A(H5N1) virus has not yet acquired this capability, but it cannot be ruled out in the future if the number of infections continues to rise," he comments.

There are still no reports of infections in Mexico; however, following the alarm raised by the initial event in the United States, Senasica has already conducted a targeted search for the A(H5N1) virus on cattle ranches.

There is currently a vaccine for farm birds that is used in high-risk situations of avian influenza outbreaks, but there is no vaccine for dairy cows or humans.

"There is no vaccine for dairy cows, as it has just been discovered that they can also be infected with the (A)H5N1 virus. Furthermore, based on what has been observed, the presence of this virus in some cows may not be such a significant problem, as it does not kill them, but only leads to a decrease in their milk production," he warns.

"As for humans, it is not yet known whether the annual seasonal influenza vaccine can mitigate the effects of infection with the A(H5N1) virus. It is reasonable to assume that it can, as all influenza viruses share common elements. However, if necessary, vaccine production platforms for this type of virus could be used to produce specific vaccines against the A(H5N1) virus or other viruses with pandemic potential," says Rodríguez Álvarez.

It is important to understand that although milk from sick cows may be contaminated with the A(H5N1) virus, the pasteurization process it undergoes destroys it along with other pathogens.

"The risk of contracting any disease from consuming pasteurized milk or dairy products (cheese, cream, butter, yogurt) made from such milk is practically zero," notes the university student.

As forIf chicken MEAT and eggs are contaminated, the A(H5N1) virus does not reach them. When a chicken or chick becomes infected with avian influenza, the microorganism is found in its saliva, secretions, and feces; and once the animal is dead and its meat is cleaned and cooked—that is, roasted, cooked, boiled, or fried—any traces of the virus are destroyed. The same applies to eggs.

"In fact, you should never eat raw chicken or eggs because they can contain"Bacteria such as Salmonella and Campylobacter, which have been linked to cases of Guillain-Barré syndrome recently diagnosed in Tlaxcala, should be avoided. Furthermore, all meats (especially chicken, beef , and pork ) should be thoroughly cooked before consumption. And it's important to maintain good cooking habits in the kitchen, such as not using the same utensils for meat and vegetables," she concludes.