Pandemics are a natural recurring phenomenon that humanity has experienced too many times. As I describe in my book “Chronicle of Viruses”, with technological development we have built a “human shell”, an environment that protects us from natural phenomena and uncertainty. However, this “human shell” is not invulnerable. The source of pandemics lies in pathogens, bacteria or viruses, transmitted to humans mainly by animals. Since we have not eliminated our interaction with animals and the rest of the natural environment, it is a given that pandemics will continue to occur. Like earthquakes that we know will happen again but don’t know when, pandemics are certain to happen again, we just don’t know the exact time. Observation and research in recent years has helped us develop surveillance tools for the various viruses that are theoretically most likely to cause pandemics. With these tools we hope to be better prepared to deal with the pandemic if and when it happens again.

Greater than 50% of people who ended up in the last five years

As part of these studies, bird flu surveillance is done by many public health agencies, which aims to predict the possibility of a pandemic with one of the flu viruses apparently deadliest to humans. Why do we say that the bird flu virus is apparently very deadly? Based on bird flu cases recorded in humans over the past five years, the figure is more than 50%. As milder cases are likely to be underdiagnosed, mathematical models estimate that the true mortality rate of avian influenza in humans is somewhere between 14 and 33%. In comparison, seasonal flu has about 0.2%, meaning the bird flu virus is at least 70 times more deadly than seasonal flu.

Why can’t the bird flu virus cause a pandemic at the moment? Because it doesn’t seem to be well adapted to humans to be transmitted between humans. So far the cases we are seeing are animal-to-human (most commonly bird-to-human) transmissions and no subsequent human-to-human transmission. The bird flu virus seems to prefer cells deeper in the lung, so it multiplies in humans to the point where it causes severe disease, but is not easily transmitted.

The fewer steps are taken to adapt the virus to humans, the sooner a pandemic outbreak can occur

For years we have been studying the behavioral changes of the bird flu virus to identify signs that show it is better adapted to humans. One point of such adaptation is the creation of epidemic outbreaks in animals more closely related to man than to birds, such as pigs and cows. Genetic relatedness plays a key role in how easily a virus can adapt to human biology and is a critical point for it to gain pandemic potential.

The last two years have seen particularly worrying signs as several species of mammals in the wild have been infected by the bird flu virus, showing clear signs that the steps the virus needs to adapt to humans are diminishing. When the steps needed for the virus to adapt to humans are fewer, this means that it is easier to happen, so it is more likely, but also that it can happen relatively sooner.

Of particular concern is the outbreak of avian influenza virus on US cow farms as it is the first time such a thing has been recorded.

Pasteurization in milk kills the virus – There is no immediate risk of transmission through the food chain

The virus is also detected in milk, however pasteurization “kills” the virus, as well as other pathogens that may be detected in milk. For this reason, it is extremely important to consume pasteurized milk over time, because it blocks any pathogens that can pass through the food chain and into humans, even those that are unknown. Therefore, so far, with the existing measures, there does not appear to be any direct risk of transmission within the food chain if and as long as the sanitary management of milk and other products from cattle is followed. Nevertheless, it shows that the virus has already taken a step closer to gaining pandemic momentum, and the chances of it “making it” have increased.

In the last week media of India (times of india) reported an epidemic outbreak of bird flu in Jharkhand where two doctors and another six close contacts of patients diagnosed with bird flu were quarantined. The patients diagnosed with bird flu were all poultry farm workers, so the virus does not yet appear to have adapted to humans. However, this incident also raises the alarm for workers in these areas to develop precautionary measures, both for themselves and to reduce the chance of transmitting a pandemic-adapted strain.

Clinical trials have begun for vaccines to be given to professionals

In any case, if the adaptation of the bird flu virus to a human pandemic strain occurs, it will be an event that we have not seen before. Since 1900, four pandemics of influenza A strains have been recorded with scientific certainty. The most severe was in 1918 known as the Spanish flu, a severity 5 pandemic, the most severe on the 5-point scale of pandemic severity. The other three were the 1957-1958 pandemic known as the “Asian” flu, followed by the 1968 (Hong Kong) flu, which came from recombination with bird flu, and finally the 2009 (swine flu) pandemic. None of the last three pandemics exceeded a 2 on the 5-point scale of severity, while the only one linked to avian influenza virus was that of Hong Kong. However, even Hong Kong flu did not have an exclusive avian flu virus origin, as it arose by recombination. Close surveillance of the bird flu virus aims to be better prepared to deal with the possibility of a pandemic by developing appropriate vaccines, as well as treatments. Already, clinical trials have begun for bird flu virus vaccines that could be given to high-risk professionals, such as workers on vulnerable animal farms. In this way, the risk of a pandemic strain will also be reduced.

Although there were two vaccines against the avian influenza virus that had reached authorization (or very close to authorization) by the European Medicines Agency, both have now been withdrawn. The former was withdrawn at an almost mature stage of evaluation for licensing, while the latter was withdrawn altogether in 2020 (although it had not been produced at all since 2010).

Both of these vaccines have been designated as pre-pandemic, vaccines that will reduce the risk of the pandemic by protecting high-risk professionals, but could also be used by the general population in the event of a pandemic. However, given the high risk of an avian influenza virus pandemic, the CDC in America has invested resources in characterizing an influenza virus that would be a suitable candidate for the development of an effective pro-pandemic vaccine.