Virus World

Pandemic hunting scientists warn of a 'perfect storm' for new diseases to emerge from wildlife. In the last 20 years, we've had six significant threats - SARS, MERS, Ebola, avian influenza and swine flu," Prof Matthew Baylis from the University of Liverpool told BBC News. "We dodged five bullets but the sixth got us. "And this is not the last pandemic we are going to face, so we need to be looking more closely at wildlife disease." As part of this close examination, he and his colleagues have designed a predictive pattern-recognition system that can probe a vast database of every known wildlife disease.

Across the thousands of bacteria, parasites and viruses known to science, this system identifies clues buried in the number and type of species they infect. It uses those clues to highlight which ones pose most of a threat to humans. If a pathogen is flagged as a priority, scientists say they could direct research efforts into finding preventions or treatments before any outbreak happens. "It will be another step altogether to find out which diseases could cause a pandemic, but we're making progress with this first step," Prof Baylis said.

Many scientists agree that our behaviour - particularly deforestation and our encroachment on diverse wildlife habitats - is helping diseases to spread from animals into humans more frequently. According to Prof Kate Jones from University College London, evidence "broadly suggests that human-transformed ecosystems with lower biodiversity, such as agricultural or plantation landscapes, are often associated with increased human risk of many infections". "That's not necessarily the case for all diseases," she added. "But the kinds of wildlife species that are most tolerant of human disturbance, such as certain rodent species, often appear to be more effective at hosting and transmitting pathogens....

Normally, bird flu viruses do not spread easily from person to person. But if this does happen, it could trigger a pandemic. Researchers from the MDC and RKI have now explained in the journal Nature Communications what makes the leap from animals to humans less likely. Whenever people suddenly become infected with a bird flu virus such as H5N1, H7N9, and H5N6, the World Health Organization (WHO) has to assess the risk: Are these the first signs of a pandemic? Or is it just a few dozen or hundred cases that have only arisen through close contact with infected poultry? Researchers led by Professor Matthias Selbach from the Max Delbrueck Center for Molecular Medicine (MDC) have now found another piece of the puzzle that may be important in this initial assessment. In a paper published in Nature Communications, the researchers explain that avian influenza A viruses (IAVs) are unable to transform infected human cells into effective virus factories, because they do not produce enough of the matrix protein M1 following infection. The virus requires this protein, however, to export its many copies of its genetic material from the cell nucleus—a prerequisite for building new viruses.

Not all flu is the same—the name refers to a large family of viruses. Each member of this family is named after two prickly growths on the virus's surface: hemagglutinin (H), which enables the virus to infect human and animal cells where it can multiply, and neuraminidase (N), which helps the virus's offspring to extract themselves from the infected cell. In waterfowl, there are 16 known hemagglutinin subtypes and nine known neuraminidase subtypes. That results in at least 144 possible combinations that are constantly changing and adapting to new hosts—like chickens, for example, but also mammals including horses, pigs, and humans. Such new virus variants are often more dangerous than seasonal flu, because the human immune system has never encountered them before. Some people find themselves defenseless, while the immune system of others reacts so violently that the person's own resistance damages the body. In the worst case scenario, a pandemic could cost millions of lives. The Spanish flu of 1918, for example, claimed more than 50 million victims. Researchers around the world are therefore trying to understand the rules that determine when there is the possibility of a pandemic, and when there is not.

Why are human cells bad factories for bird flu? "Hemagglutinin in humans and birds has a slightly different chemical structure, for example, which makes it more difficult for an avian influenza virus to infiltrate a human cell than a bird's cell," explains Selbach. Boris Bogdanow, a Ph.D. student in Selbach's research group and the lead author of the current study, focused his research specifically on what other natural species barriers exist in flu viruses. But the devil is in the detail, so Bogdanow performed more in-depth analyses to take a closer look at the protein distribution. In doing so, he came across the matrix protein M1, much larger quantities of which were produced in the lung cells infected with the human virus. The M1 protein is responsible, among other things, for exporting the replicated viral RNA from the nucleus of the infected cells and then assembling it with other newly produced viral proteins to form flu virus offspring. Could it be, then, that the viral RNA of bird flu viruses in human cells remains trapped in the cell nucleus because too little M1 protein is present?....

Published in Nature Communications (04 December 2019):

https://doi.org/10.1038/s41467-019-13520-8

As humans have spread across the world, so have infectious diseases. Even in this modern era, outbreaks are nearly constant, though not every outbreak reaches pandemic level as the Novel Coronavirus (COVID-19) has. Today’s visualization outlines some of history’s most deadly pandemics, from the Antonine Plague to the current COVID-19 event.

Disease and illnesses have plagued humanity since the earliest days, our mortal flaw. However, it was not until the marked shift to agrarian communities that the scale and spread of these diseases increased dramatically. Widespread trade created new opportunities for human and animal interactions that sped up such epidemics. Malaria, tuberculosis, leprosy, influenza, smallpox, and others first appeared during these early years. The more civilized humans became – with larger cities, more exotic trade routes, and increased contact with different populations of people, animals, and ecosystems – the more likely pandemics would occur. Here are some of the major pandemics that have occurred over time....