Avian influenza pathogens pose an unsettling threat to human health, in particular due to their innate ability to multiply in thermal conditions that are beyond the body’s immune system’s barricade caused by fever. New research led by researchers of The Universities of Cambridge and Glasgow reveal this awe-inspiring characteristic, highlighting the mechanisms of viral infection that permit the bird flu strains to evade one of the oldest defense reactions.
The study was published by Science researchers have identified the key gene responsible for the way a virus reacts to changes in temperature. During the devastating flu pandemics of the years 1957 and 1968, the same gene mutated into human flu strains, providing the virus with a tolerance to heat and causing widespread destruction across the globe.
In the human body seasonal influenza A virus is most often found within the airways of upper respiratory tracts, an area which is at or near 33°C. They do not thrive in the deeper airways in which temperatures can reach around 37 degC. Inflammation, which can increase body heat to extreme temperatures of 41degC, is the natural thermal assault designed to thwart the replication of viruses. But avian influenza thwarts this biological strategy with alarming ease.
Human flu strains are less effective at higher temperatures. The avian influenza virus thrives in much hotter areas. The hosts of their avian hosts – gulls ducks, and waterfowl — these virus thrive in the gut where temperatures typically peak at 40degC to 42degC. The previous laboratory tests with cell cultures suggested the possibility of this heat resilience, but until recently, the actual mechanisms were not fully understood.
In the current study scientists created fever-like conditions for mice by subtly increasing the temperature of the air around them. Using PR8, a laboratory-honed human-origin influenza strain, they observed that mimicked fever effectively stifled viral replication–transforming what would have been lethal infections into far milder events. But, the avian influenza strains showed remarkable durability in overcoming these extreme conditions while causing grave illnesses.
The most important revelation came from looking at the PB1 gene, a segment of the genome of viruses essential for replication within host cells. If influenza strains contained PB1 variants that resembled those found in Avian viruses, they retained their strength even at fever-like temperatures, causing severe disease. This is a significant discovery that has important implications that avian and human flu virus can share genes while co-infecting an unrelated host, like porcines, resulting in hybrid strains that can outlast the human immune system.
Professor. Matt Turnbull, the study’s principal author Dr. Matt Turnbull, the study’s lead author from Dr. Matt Turnbull, the study’s lead author from Medical Research Council Center for Virus Research Dr. Matt Turnbull, the study’s lead author from the Medical Research Council Center for significance of the swapping of genes in viral infections. He noted that previous pandemics occurred precisely because human-strain viruses appropriated avian PB1 segments–potentially explaining their unusually deadly clinical outcomes. He emphasized the necessity of examining the bird flu strains to determine their ability to withstand heat, in order to identify strains with high risk.
Prof. Sam Wilson, senior author from the Cambridge Institute for therapeutic Immunology as well as Infectious Disease cautioned that, while human infections remain rare however, the rate of mortality for H5N1-related cases from the past is over 40%. This is an unsettling warning of the danger present in avian flu reservoirs. He emphasized that understanding the reason why certain strains of bird influenza cause devastating human illness is essential to ensure that pandemic surveillance is on the right track.
The study also suggests potential clinical implications. Certain medications for reducing fever-like symptoms, like ibuprofen or aspirin — are widely used but evidence is mounting that they can weaken the body’s defenses and may increase the rate of viral transmission. While researchers aren’t in the business of recommending changes to treatment however, they call for a deeper investigation into the way that fever-management strategies affect the outcome of influenza.
This research uncovers a disturbing fact: some avian influenza virus strains are designed to withstand the heat of fever, and are able to bypass one of the most ancient protection mechanisms. As global surveillance grows the need to understand these strategies to defy heat could be the cornerstone of the pandemic’s preparedness.
