A common cold virus that can land babies in the hospital may hide out in the lungs for weeks or months, perhaps explaining how it spreads easily despite the best hygiene efforts, doctors reported Friday.
They found evidence that respiratory syncytial virus, or RSV, stays in the lungs of mice long after they seem to be over the main infection.
Doctors had thought that RSV survived in the body for only a few days. But this study, published in the American Journal of Respiratory and Critical Care Medicine, suggests it hides itself inside the lungs.
A 'hit and hide' virus
“These studies show that RSV is a 'hit and hide’ virus, rather like HIV, herpes or some hepatitis viruses,” said Dr. Peter Openshaw, of Imperial College London and St. Mary’s Hospital, who worked on the study.
“The symptoms seem to go away but the virus is just hiding, waiting for a chance to re-emerge and begin infecting other people,” he said in a statement.
RSV infects virtually every child by age 2 and is the most common cause of bronchiolitis and pneumonia among infants. Like other cold viruses, it causes fever, cough, runny nose and wheezing.
The first time they are infected, between 25 percent and 40 percent of babies have some symptoms of bronchitis or pneumonia and up to 2 percent are ill enough to be hospitalized. Some end up on ventilators to help them breathe.
RSV causes mild symptoms in healthy adults but can cause severe illness in the elderly or those with damaged immune systems such as patients with HIV or on cancer therapy.
Some patients may act as carriers
Openshaw and colleagues in Germany infected mice with human RSV and observed that after 14 days, the virus could no longer be found in samples taken from the airways.
But traces of the virus’s genetic material, called viral RNA, could be found in the lung tissue more than 100 days later.
The same is probably true in people, the researchers said. It is possible that children who no longer have immediate symptoms of colds such as coughs and fever may have RSV lurking in their lungs, they said.
“Some people may be 'carriers’, able to act as a source of new outbreaks in children,” Openshaw said.
“If RSV is a 'hit and hide’ virus, this could explain where this virus goes in the summer and where it comes from each winter. If the virus is able to lie dormant in previously infected individuals, it could re-emerge when the conditions are right and cause the outbreaks that fill our children’s wards each winter.”
