Find out why H5N1 causes high mortality in humans

The mechanism of death of avian influenza virus is similar to that of a pandemic flu in 1918, which is " submerging " patients in large amounts of lung-producing fluids - research at HCMC Tropical Diseases Hospital said.

Since 2003, the world has recorded 241 cases of bird flu due to H5N1, more than 50% of these deaths. Previously, scientists did not know why H5N1 was so deadly.

H5N1 virus (Photo: rfi.fr)

To find out, Dr. Menno de Jong, a virus expert from the Oxford University Clinical Research Unit (UK) and his colleagues conducted a study of 27 cases of influenza infection at the TPD Hospital. HCM. Of these, 18 were infected with H5N1 virus and 9 were infected with regular seasonal influenza virus.

'Cytokine storm'

The team found that patients with bird flu, especially 13 deaths, had abnormally high levels of the H5N1 virus in their bodies. Consequently, blood levels of chemicals called cytokines and chemokines are also very high. Normally these chemicals are responsible for attracting white blood cells to destroy the enemy, but if too much is present in the blood, they will cause the immune system's response to become excessive, causing the lungs to become watery, causing inflammation. deadly lungs.

'Cytokine storm' is the leading hypothesis that scientists choose to explain why in the 1918 Spanish flu pandemic, so many young people - completely healthy before - died. While seasonal flu tends to be fatal in the elderly and young children, it is often due to bacterial infections that occur many days after the influenza virus (not very dangerous) stimulates lung tissue.

'Strike hard, hit immediately'

According to the team, for patients with H5N1 infection, immediate treatment with antiviral drugs is particularly important. The reason is that because the virus produces extremely rapidly, if it is not suppressed within the first 48 hours, they will quickly push the patient to death.

The motto " hit hard, hit immediately " seems to be very true for the flu caused by H5N1 - Mr. de Jong commented. However, according to him, because the body's own immune response also contributes to injury, doctors need to consider the combination of anti-inflammatory drugs with anti-viral drugs like Tamiflu.

Flu viruses are abundant in the throat

Scientists were surprised to find a lot of H5N1 viruses in specimens taken from the nose and throat, especially the throat. Previous studies show that, unlike seasonal flu, avian influenza viruses are not easily spread from person to person because they have been closely linked to receptors deep in the lungs from the beginning. According to Dr. de Jong, this can be explained as follows: The H5N1 virus has gone from the lungs to the throat when the patient coughs.

Unlike the seasonal flu virus commonly found in the nose, H5N1 is easier to find in the throat. This finding helps many doctors in taking specimens. In addition, influenza viruses are also found in samples taken from the rectum. This is also important because it shows that diarrhea - a common symptom in flu patients - may also be a pathogen of the disease.

The study also found that some strains of influenza isolated in Vietnam have special genetic changes that can make them more toxic. However, these changes only appear in a few patients, even in cases of death and survival. So the research team has not drawn any conclusions about this issue.

According to a report published in Nature Medicine in October, according to experts, this is an "important step" because so far there is so little clinical information regarding 241 H5N1 cases that have been brightened. show.

Thu Thuy