Enterovirus D68 (EV-D68) has not garnered the media attention that Ebola virus has; however, it is more likely that you’ve encountered a patient with symptoms consistent with EV-D68. Unfortunately, fever, cough, runny nose, sneezing and body aches does not make for an open and shut diagnosis. In addition, it is likely that patients and families are on high alert and have many questions, especially with the cases of neurologic illness recently reported by the Centers for Disease Control and Prevention (CDC). For these reasons, we thought a background on enteroviruses might be of interest.
A family of viruses
Enteroviruses are part of the Picornaviridae family. Viruses in this family are small-sized, single stranded RNA (ssRNA) viruses. The Picornaviridae family consists of 12 genuses, and within the enterovirus genus, 10 different species have been classified. Poliovirus, coxsackievirus and rhinoviruses are in the same genus as EV-D68.
- Enterovirus D68 - species within the genus, human enterovirus D
- Polioviruses - species within the genus, human enterovirus C
- Coxsackieviruses - species within the genus, human enterovirus A and B
- Rhinoviruses - species within the genus, human rhinovirus A, B and C
Characteristics of enteroviruses
Enteroviruses are fairly hardy. So they aren’t easily inactivated by common disinfectants, such as 70 percent ethanol, isopropanol, dilute Lysol® or quaternary ammonium compounds. Additionally, ether, chloroform and many detergents are also ineffective. As a general rule, enteroviruses are most effectively inactivated by formaldehyde, glutaraldehyde, strong acids, hypochlorite and free residual chlorine. However, a variety of factors play a role in the effectiveness of inactivation, such as concentration, pH, extraneous organic materials and contact time. Because enteroviruses tend to be sensitive to higher temperatures, pasteurization is effective for inactivating the virus in biological preparations. Ultraviolet light can inactivate the virus on surfaces and, generally speaking, viral titers decrease significantly when the virus dries on surfaces.
The two primary routes of infection for enteroviruses are respiratory and gastrointestinal (fecal-oral). In the case of EV-D68, the infection is primarily at respiratory sites. Therefore, transmission during the current outbreak is mostly expected to be through respiratory means – coughing, sneezing or self-inoculation through touching a contaminated surface or item and then touching one’s face.
Because of the relative hardiness of these viruses, the best way to avoid infection is to prevent inoculation by avoiding people who are sick, washing hands frequently, not touching one’s face with unwashed hands, and regularly cleaning objects that are touched often particularly by many people, such as doorknobs and toys. Patients with asthma should be also encouraged to maintain daily therapies.
Enterovirus D68 and other respiratory infections
More than one type of enterovirus is circulating and, of course, other respiratory viruses are also circulating. Typically, enteroviruses circulate between late summer and fall, so it is likely that they will soon be decreasing. However, an almost simultaneous uptick in influenza may make the appearance of infections characterized by respiratory symptoms seem steady.
Younger children, and those with respiratory conditions such as asthma, are more likely to suffer severe symptoms. However, those with asthma may also be more likely to suffer complications from infections with influenza or pneumococcus. Therefore, if a patient presents with severe respiratory illness and an unclear cause, EV-D68 testing may be considered.
Enterovirus D68 and antivirals
Unfortunately, antiviral drugs that have been effective in treating other enteroviruses have not been effective against EV-D68 when tested at clinically relevant concentrations. Therefore, guidance should be to treat symptoms, and if the person has trouble breathing, he or she should seek emergency treatment.
Enterovirus D68 and recent cases of neurologic illness with limb weakness
Recent cases of neurologic illness with limb weakness are being investigated; however, it is still unclear whether these cases are causally associated with the ongoing EV-D68 outbreak. Enteroviruses are a known cause of neurologic illness in children; however, EV-D68 has previously been detected in cerebrospinal fluid (CSF) in a limited number of cases. However, among a cluster of nine patients in Colorado in August, CSF did not contain EV-D68, but 4 of 8 respiratory samples were positive for the virus. Because enteroviruses are common enough that sometimes they can be detected in healthy people, this finding alone does not establish causality between the neurologic illness and EV-D68 infection. The CDC continues to investigate these cases and has requested that clinicians report any patients with the following criteria to their state or local health department immediately:
- Patient is younger than 21 years old.
- Patient experienced an acute onset of focal limb weakness.
- The symptoms occurred on or after August 1, 2014, AND
- An MRI reveals a spinal cord lesion largely restricted to gray matter.
Additional CDC resources