Two common respiratory viruses can merge to form a hybrid virus capable of evading the human immune system and infecting lung cells. This is the first time, experts have observed the two viruses cooperate like this.
These findings may explain why co-infection can lead to significantly worse disease for some patients.
Each year, approximately 5 million people worldwide are hospitalized with influenza A, while respiratory syncytial virus (RSV) is the leading cause of acute lower respiratory tract infections in children under 5 years of age.
According to the Guardian , co-infection – a person infected with both viruses at the same time – is relatively common. However, it remains unclear how these viruses would act if they were in the same cell.
Dr Joanne Haney, from the University of Glasgow’s MRC Virus Research Center, explains: “We need to understand how infection is transmitted to get a fuller picture of the biology of individual viruses.”
Dr. Haney and colleagues note that, instead of competing with each other like some other viruses, influenza and RSV viruses combine to form a palm-shaped hybrid virus.
“This hybrid virus has never been described before,” said Professor Pablo Murcia, who evaluated the study published in the journal Nature Microbiology .
Once formed, the hybrid virus can also infect neighboring cells – even in the presence of antibodies to the flu.
In addition to helping the virus evade the immune system, the combination of the two viruses also allows them to reach a wider variety of lung cells. If flu normally infects cells in the nose, throat, and windpipe, RSV is more likely to attack cells in the trachea and lungs – although there is some overlap.
Dr Stephen Griffin, a virologist at the University of Leeds, said hybrid viruses increase the risk of severe lung infections and even death: “It’s one reason you try to avoid multiple viruses, because hybridization is more likely if we don’t take precautions to protect our health.”
“We need to know if this only happens with influenza and RSV, or spreads to other virus combinations,” said Prof Murcia. This is just the beginning of what I think will be a long journey.”