The Enterovirus D68 outbreak appears to be waning

According to USA Today, it appears as though the Enterovirus D68 (EV-D68) outbreak in the U.S. is waning:

"In every measure counted by Flu Near You, an online tracking site run by Boston Children's Hospital and Skoll Global Threats Fund, children's symptoms have declined compared with a peak three weeks ago. Fevers are down, coughs and breathlessness have been cut by more than half, and the number of children going to the doctor with multiple symptoms has fallen from 4.5% to 2%, according to data from associate professor John Brownstein, who is on the team that runs the website.

The information matches what's happening in Colorado, which was one of the hardest-hit states, said Larry Wolk, chief medical officer and executive director of the Colorado Department of Public Health and Environment. Cases of enterovirus are starting to level off there, he said."

This assessment has been confirmed by the CDC. As I mentioned earlier, the main reason for the decline is that enterovirus infections are seasonal (i.e. responsible for summer colds), and tend to drop in the fall. The optimal temperature range for enterovirus is higher than for rhinovirus, which is primarily responsible for winter colds.

An additional piece of good news is that the CDC has developed a faster and easier diagnostic test for EV-D68. The official numbers have severely underrepresented the number of cases because general hospitals could not make the diagnosis on their own; up to now, they have relied on sequencing the virus DNA which only the CDC and other specialized health labs could do. The new diagnostic is likely to increase the official numbers of EV-D68 infections even though the outbreak is waning, but it will help public health officials more accurately track cases.

Tragically over the last month, several children have died from EV-D68. This is thought to be because the very large number of cases have produced a few very severe cases. In addition, there have been concerns linking EV-D68 to a small number of cases involving partial paralysis. The cause of this partial paralysis has been the subject of debate because only some (~1/2) of the patients have tested positive for EV-D68; the others have been infected by other enteroviruses or rhinovirus. It is possible that the EV-D68 diagnostic was not sensitive enough to detect virus in the non-positive patients. Alternatively, the more likely explanation is that EV-D68 may not be the sole culprit, but among the large number of EV-D68 cases, a few may have resulted in infection of the spinal cord. Note that enterovirus and rhinovirus belong to the same family as polio virus. With time doctors are hoping that the kids can recover from the partial paralysis symptoms.

As the number of cases decline, then there will be less danger of the more serious infections. Hopefully next year the outbreak of the "summer cold" will be less severe.

Figure 1. With the decline in EV-D68 cases, scenes like this will become less common.