The Week That Wasn't: Virus Cream, Commute Chemicals, Tracing Mumps

Ellie Kincaid

February 14, 2020

You may have recently seen articles about a skin cream that could protect against infection from mosquito-borne viruses, commutes exposing drivers to harmful chemicals in car seats, and how researchers used gene sequencing to link seemingly separate outbreaks of the mumps in Boston. Here's why you didn't see them on Medscape.

Skin Cream to Block Mosquito-Borne Virus Infection

Many viruses that can make people sick spread via mosquito bites: chikungunya, dengue, and Zika, to name a few. Applying topical imiquimod, a drug approved for actinic keratosis and genital warts, one hour after a mosquito bite reduced viral replication in mice and in vitro human skin biopsy models, researchers reported in the journal Science Translational Medicine. By limiting viral replication in the hours after infection, the hope is that applying the skin cream to the site of a mosquito bite could prevent a systemic infection.

It's often exciting when scientists find a new use for a medication that's already available, and even more so when the clinical need is clear, as in this case. But because there's not yet data showing topical imiquimod works to treat mosquito-borne viral infections in people, we thought it was premature to alert our readers to the possibility.

Chemical Exposure While Commuting

Could spending more time commuting in a car be a health hazard as well as a sanity hazard? That's the idea behind a study published in Environment International, in which research participants wore silicone wristbands to monitor their exposure to organophosphate esters, chemicals that are used as flame retardants in car seats. One organophosphate ester, tris(1,3-dichloro-2-propyl) phosphate (TDCPP), is considered a carcinogen under California's Proposition 65, and the researchers found longer commute times were associated with increased exposure to this chemical. "Our findings raise concerns about the potential for chronic TDCPP exposure within vehicles and other forms of transportation," they write.

The California Office of Environmental Health Hazard Assessment recognizes an exposure of 5.4 µg of TDCPP per day as posing "no significant risk level," and not requiring a warning of carcinogenicity. The maximum exposure to TDCPP researchers measured in this study does not appear to have reached that level, so it's unclear what, if any, hazard the chemical poses to commuters. Considering that the hazard of car accidents is likely of higher concern, we didn't think our clinician readers needed to worry themselves or their patients about TDCPP exposure from car seats. Commuting is stressful enough already.

Understanding Mumps Outbreaks

Two mumps outbreaks in Boston that occurred between 2016 and 2017 were actually a single outbreak, researchers found when they sequenced and studied viral genomes collected from patient samples. The Massachusetts outbreak, which included more than 420 reported cases (compared to a usual statewide incidence of fewer than 10 annual cases), raised concerns that the mumps virus had mutated to become less susceptible to the measles-mumps-rubella (MMR) vaccine. The genomic analysis did not turn up any evidence such "vaccine escape" happened. "What it seems to suggest is this is waning immunity, and not vaccine escape," lead researcher Pardis Sabeti, MD, DPhil, of Harvard University and the Broad Institute, told Reuters.

As the current outbreak of COVID-19 makes clear, getting information about what's happening in the midst of a viral outbreak is crucial for public health workers to organize an appropriate response. This newly published research, although it may have been helpful in managing the previous outbreak, doesn't change how clinicians should respond to cases of mumps going forward, so we didn't feel the need to communicate it to our readers.

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