The most iconic thing about measles is the rash — red, livid splotches that make infection painfully visible.
But that rash, and even the fever, coughing and watery, sore eyes, are all distractions from the virus’s real harm — an all-out attack on the immune system.
Measles silently wipes clean the immune system’s memory of past infections. In this way, the virus can cast a long and dangerous shadow for months, or even years, scientists are finding. The resulting “immune amnesia” leaves people vulnerable to other viruses and bacteria that cause pneumonia, ear infections and diarrhea.
“The virus preferentially infects cells in the immune system that carry the memory of previously experienced infections,” [virologist Rik] de Swart says. Called memory B and T cells, these cellular protectors normally remember threats the body has already neutralized, allowing the immune system to spring into action quickly if those threats return. After a measles infection, the numbers of some types of these memory cells dropped, creating an immune amnesia.
The immune system might take months, or even years, to bounce back from this memory loss.
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