It's respiratory syncytial virus (RSV) time again
I’ve written before (here and here) about the reliable winter time arrival of RSV. This virus is the most common cause of pneumonia and bronchiolitis in children under six months of age. To scientists, RSV is a fascinating virus with several unique properties.
One of these is its behavior in the population. During its annual visitation, RSV is everywhere. Then it suddenly vanishes. There are exceptions to everything in medicine — I have seen sporadic cases during the off-months — but generally RSV arrives with a bang in mid-winter and then leaves suddenly in the spring. It is the only virus that consistently and reliably causes an epidemic every single year. Not even influenza does that. However, RSV epidemics may still have some regional variability. For example, often one city will have a much more severe epidemic than do others in other regions of the country.
Another aspect of RSV that interests medical scientists is how poor a job our immune systems do in fighting it off. Virtually all children are infected with RSV during the first year of life. Not only that, all of us are reinfected multiple times during our lives. Attempts at devising a vaccine for RSV have all been unsuccessful. In fact, early versions of an experimental vaccine seemed to make the disease worse in some infants, raising the possibility that some aspect of our immune response to the virus actually contributes to the symptoms.
RSV has a high attack rate — the term scientists use for the chances that a susceptible person will get the infection if exposed to it. That, plus our generally poor defenses against it, explain the frequent epidemics.
RSV is generally not a serious illness, but for some children it can be life-threatening. These children are very small infants, especially those born prematurely, and those with underlying problems with their lungs or their hearts. For those infants we have a monthly shot that helps reduce the severity of RSV when they get it, and may even prevent a few cases, but this is not ideal.
Since RSV cannot be prevented, the best thing a parent can do is try to postpone it. That is, if you have a newborn infant in the height of RSV season, try to minimize exposure of your child to people with cold symptoms, especially toddlers. And for those who do handle your infant, have them wash their hands first.