It has been known for quite a while that certain viruses such as respiratory syncytial virus (RSV) and rhinovirus (the common cold) have been associated with the development and/or worsening of asthma. Both of these viruses are RNA viruses. This fact led researchers to wonder about certain DNA viruses. The one most recently studied is polyomavirus. This virus is widespread and consists of 117 species. Once thought to be totally innocuous, it is now understood that these viruses can cause clinical illness in people with compromised immune systems. But people with normal immune systems don’t have a clinical illness. However, now it seems that some of these asymptomatic infections can be either helpful or hurtful. Two of the viruses: KIPyV and HPyV6 have been shown to confer protection from children developing eczema; whereas, a different virus WUPyV is associated with a strong proclivity for children to develop asthma.
What is really weird is where these viruses infect a child. The KIPyV and HPyV6 infect the skin while the WUPyV infects the lungs. It seems that this is what makes the difference. The immune response to the virus can either help or hurt. So, even though healthy children exhibit absolutely no symptoms from these infections, their immune response to the viruses can have either a protective or harmful effect in terms of allergy. Researchers want to extend these findings especially in terms of finding the “friendly and protective” viruses.