In case you missed them, here are our top 5 articles for the week of April 23, 2017.
The Top 5 articles this past week honed in on the mosquito-borne viruses yellow fever and Zika virus, in addition to meningococcal disease and human papillomavirus (HPV). The first article brings attention to the potential for yellow fever to become a transcontinental threat, while our second article focuses on why a specific meningococcal vaccine was administered during an outbreak at Rutgers University in 2016. The third most-read article of the week includes information on a team of researchers, including Contagion®’s own Editorial Advisory Board member, Adriano de Bernardi Schneider, MS, who used computational modeling tools to phylogenetically map the evolution of the Zika virus, and shed some light on why it is causing birth defects and Guillain-Barré syndrome in adults. In addition, our second most-read article of the week highlights research from the Centers for Disease Control and Prevention which revealed new information that will help to determine whether cases of Zika virus are locally-acquired or travel-related. This will help with prevention efforts in the United States. Finally, our top article of the week covered research from the 2017 CDC EIS Conference which showed the first statistical evidence that the HPV vaccine is providing herd immunity against infection in the target population.
Concerns continue to mount in the healthcare community over outbreaks of yellow fever that are plaguing Africa and the Americas. In fact, yellow fever is the most severe of the five emerging and reemerging arthropod-borne viruses that are spreading rapidly throughout the Americas, particularly in populations that have not previously been exposed to them (such as urban centers where the vaccine for the virus is not regularly administered).
The virus has infected hundreds of individuals in Brazil, and is to blame for more than 200 deaths. Although public health officials are not concerned about an outbreak in the continental United States, Puerto Rico remains vulnerable to the virus and, “travel-related cases of yellow fever could occur, with brief periods of local transmission in warmer regions such as the Gulf Coast states, where Aedes aegypti mosquitoes are prevalent.”
To prevent future outbreaks in Brazil and other areas around the world, healthcare officials are calling for rapid and early identification of cases as well as “implementation of public health management and prevention strategies, such as mosquito control and appropriate vaccination.”
In related news, the World Health Organization and Institut Pasteur are calling attention to a case of an alarming case of yellow fever and Japanese encephalitis virus coinfection discovered in a 19-year-old male from Angola with no history of travel. Researchers from both organizations warned that “increased levels of population movement between Asia and Africa may provide opportunities for pathogens to expand their geographic range.” Although this is only one case of coinfection, “Angola has suitable vectors and hosts for Japanese encephalitis, [and so] increased serosurveillance is advisable.”
Read more about the transcontinental threat of yellow fever here.
Whole-genome sequencing enabled individuals at Rutgers University to receive personalized vaccines against meningococcal infections discovered in two undergraduate students in the spring of 2016. A specific meningococcal vaccine called Trumenba was recommended and administered to around 35,000 individuals throughout the university.
The two vaccines that are currently available to treat meningitis in the United States are a 2-dose series of Bexsero (MebB-4C) or a 2- or 3-dose series of Trumenba (MenB-FHbp). Either drug can be used for outbreak response; however, because each vaccine targets different antigens, they are not interchangeable. “The same brand must be used for all doses” when vaccinating an individual.
Because whole-genome sequencing of the samples taken from the two infected students revealed that the antigens in their samples were a mismatch for the antigen targeted by Bexsero, healthcare officials were concerned that vaccine would not provide viable protection. “Although the outbreak strain antigens also did not exactly match those included in Trumenba, cross-protection with Trumenba was expected based on prior testing by the manufacturer,” and therefore, healthcare officials chose that vaccine as the more viable option. Further testing revealed that a 3-dose course of the vaccine would offer the best protection against the outbreak strain.
Learn more about this rare exception to the general recommendation for meningococcal vaccination here.
Using Nvector, a suite of tools that solve geographical positioning, Contagion® Editorial Advisory Board member and PhD candidate, Adriano de Bernardi Schneider, MS, and his research team started tracking the genetics of the Zika virus’ spread across the world in the first months of 2016. The team was able to “phylogenetically demonstrate that the viral sequences obtained from Zika as it crossed the Pacific Ocean (and subsequently radiated across northern Latin America and the Caribbean) were unlikely to be derived from the African strain of the virus, which was first described in 1947.” In fact, “the sequences from Brazilian and Pacific Island Zika isolates clearly clustered as a different strain, or clade, and were found to be more closely related to the historic Asian rather than the historic African isolates.”
In addition, the team utilized their computational modeling tools to shed some light on why the virus was causing birth defects in infants and Guillain-Barré syndrome (GBS) in adults. With the help of additional researchers, the team “identified a set of mutated viral sequences encoding predicted epitopes with homology to epitopes predicted for human neural development-related proteins: NDF4 (Neurogenic differentiation factor 4) and Nav2 (Neural navigator protein 2). Based on this observation, we raised the hypothesis that epitope mimicry may contribute to both congenital Zika syndrome as well as GBS.” One characteristic of epitope mimicry is an autoimmune response in the affected host. This “clinical autoimmunity can occur when virus proteins are similar to human proteins.”
Continue reading more about the teams findings about the Zika virus here.
Although the majority of Zika virus infections in the United States have historically been travel-related, the approaching warmer months will bring with them mosquitoes and thus renewed fears of locally-acquired infections. Researchers may have now discovered a better way to determine whether a case of Zika virus was truly acquired locally, or if it came in through travel to a Zika-endemic region.
Indeed, a new analysis from the Centers for Disease Control and Prevention (CDC) has provided more information on the differences seen in locally-acquired vs travel-related cases. For example, the researchers “found that among symptomatic Zika-infected travelers, 99% experience symptoms within 2 weeks of exposure, and 50% within 1 week.” Therefore, the researchers recommended that those individuals who develop Zika-associated symptoms “more than 2 weeks after travel to a Zika-endemic area ‘should be evaluated for alternative modes of transmission.’” It is this aspect—evaluating individuals for alternative modes of transmission—that is key to helping epidemiologists identify locally-acquired cases sooner, and aiding in more rapid implementation of vector-control strategies. In addition, the results of the study suggested that “the incubation period for the Zika virus is between 3 and 14 days.”
In a related study, researchers have found evidence to support the use of whole blood over plasma samples for the molecular diagnosis of acute symptomatic and asymptomatic Zika virus infections as “the use of whole-blood specimens is much more sensitive than the use of plasma samples to detect Zika virus RNA.” In addition, the data from the study could be useful for analyzing “the safety of whole blood and blood components from donors, as well as for the safety of organs, tissues, and cells from deceased and living donors.”
More information on the incubation period of and optimal testing methods for the Zika virus is available here.
Research recently presented at the 2017 Epidemic Intelligence Service (EIS) Conference in Atlanta, Georgia provided the first statistical evidence for herd protection as a result of human papillomavirus (HPV) vaccination. The study was conducted over the course of 11 years and evaluated the effectiveness of the vaccine in females.
Lieutenant commander Sara Oliver, MD, MSPH, and her team “used National Health and Nutrition Examination Survey (NHANES) demographic and self-reported vaccination data along with HPV DNA gleaned from self-collected cervicovaginal specimens to estimate HPV prevalence during three distinct eras: the pre-vaccine era, early-vaccine era, and recent-vaccine era.” Among the 18- to 24-year-old women in the pre-vaccine era group, HPV prevalence was 18.8%, compared to 16.9% in the early-vaccine era, and 7.1% in the recent-vaccine era. That vaccine type prevalence decreased in non-vaccinated females indicates herd protection. No significant changes or differences in the sexual behaviors of unvaccinated vs vaccinated women were noted.
Although an overall decline in the presence of HPV was noted, “a relatively higher prevalence of HPV in the unvaccinated population indicates that ‘HPV is not just going away anyway.’” Therefore, Dr. Oliver encouraged healthcare providers to continue to make strong recommendations to get adolescents vaccinated.
Read more about the results of this HPV study here.