News Scan for Jan 17, 2018

Antivirals for nursing home flu
Dengue immunity after Zika
Zika in various mosquitoes
Ebola vaccine animal trial

Study: Early antivirals can cut the size of nursing home flu outbreaks

Starting antiviral treatment early may reduce the size of flu outbreaks in long-term care facilities, researchers from Taiwan reported today in Influenza and Other Respiratory Viruses.

In their retrospective cohort study, the team analyzed electronically filed investigation reports of flu outbreaks that occurred at Taiwan's long-term care facilities from 2008 through 2014. Interventions included treating sick patients with antivirals and providing antiviral prophylaxis to contacts during outbreaks. The scientists noted that the using antivirals to curb outbreaks became more common in Taiwan in the wake of the 2009 H1N1 pandemic.

Of 102 flu outbreaks that were reported during the study's span, the median number of days from outbreak onset to outbreak notification was 4, with a range of 0 to 22. Median vaccination coverage among facility residents was 81%, ranging from 0% to 100%. The team found that the median attack rate was 24%, ranging from 2.2% to 100%. Though antiviral treatment was given in 87% of the outbreaks, the staff offered antiviral prophylaxis in only 40%.

Starting antiviral treatment within 2 days of an outbreak's start was associated with keeping attack rates below 25%, cutting the risk of an event developing into a large outbreak to about one-third. They noted that Taiwan doesn't have guidance on antiviral prophylaxis use in long-term care outbreak settings, officials have concerns about increased drug resistance and the cost of the drugs. Hence, decisions on using antivirals for prophylaxis are usually made on a case-by-case basis.
Jan 17 Influenza Other Respir Viruses abstract


Brazil study hints at dengue cross-protection in Zika's wake

An outbreak of Zika virus in 2015 in Brazil may have provided some cross-protection against dengue infection, according to researchers who studied disease surveillance data in a slum community of Salvador, the country's fourth-largest city. The team's findings appear in a letter published in the February issue of The Lancet Global Health.

The group has done continuous surveillance among patients with acute febrile illness since January 2009, except for a temporary gap in research funding and a temporary closure of the health center for maintenance. Before 2015, positive tests for dengue virus followed annual second- or third-quarter peaks However, they saw a much smaller peak in 2015 during the Zika outbreak, with dengue positive showing no peak in 2016 and 2017. The frequency of confirmed dengue in patients with febrile illness fell from 25% before the Zika epidemic to 3% after the outbreak.

However, over the same period, the percentage of patients who tested positive for chikungunya virus infection increased significantly from 7% before the Zika epidemic to 20% after, suggesting that the environmental conditions, including mosquito populations, were still in place after the Zika epidemic.

Citywide data also showed a drop in dengue serological or virological positive— from 31% before the Zika outbreak to 8% after. During the same period, the city had two large chikungunya peaks after the Zika outbreak, one in mid-to-late summer and one in mid-to-late fall.

"Although temporal associations do not prove causation, the strength and consistency from both enhanced surveillance and citywide data, together with the observed maintenance of high detection of chikungunya virus after the Zika virus outbreak, suggest that Zika virus infections could induce cross-protective immunity against dengue virus," the group wrote.
February Lancet Glob Health letter


Scientists find Zika virus in 3 mosquito species not known to carry it

Zika virus was discovered in the salivary glands of five mosquito species caught in the wild in Mexico, including three previously unreported, according to a study yesterday in Scientific Reports.

Though Aedes aegypti and Ae albopictus are the main vectors of the disease (and also transmit dengue, chikungunya, and yellow fever), other species have been theorized to be able to carry the Zika virus, as well. Mexican researchers looked at Ae aegypti and Ae vexans, as well as Culex quinquefasciatus, Cx coronator, and Cx tarsalis.

They collected 579 mosquitoes over 5 separate days from September to November 2016 in different parts of the Guadalajara metropolitan area. They were able to isolate in cell culture Zika virus from different body parts—including the salivary glands—of female mosquitoes representing all five species and in whole male Ae aegypti and Cx quinquefasciatus mosquitoes.

The authors conclude, "To the best of our knowledge this is the first report that shows the presence of ZIKV [Zika virus] in the salivary glands of wild-caught female mosquitoes Cx. coronator, Cx. tarsalis, and Ae. vexans, as well as and in Ae. aegypti and Cx. quinquefasciatus, which have already been reported as potential vectors for ZIKV.

"Additional studies of female mosquitoes' saliva from the different species reported in this work are needed to confirm the presence of ZIKV and determine if they have a vector competence barrier to the virus."
Jan 16 Sci Rep study


Ebola vaccine proves effective in non-human primate challenge

A single-dose modified vaccinia Ankara Ebola vaccine protected macaques from Ebola virus after experimental infection, according to a separate study yesterday in Scientific Reports.

In the study, 12 primates were challenged with Ebola virus Makona, strain in both a prime and booster dose. While six control animals contracted Ebola virus, the immunized monkeys all showed high levels of Ebola immunoglobulin G (IgG) and did not contract the virus.

This is the first study to demonstrate the effectiveness of a novel recombinant modified vaccinia Ankara (MVA)-based vaccine containing Ebola-like particles. MVAs have previously used in ring vaccination campaigns to help eradicate smallpox.

"The MVA-EBOV vaccine could be very useful—not only for containing an outbreak by emergency immunization, but as a routine vaccine for a target population in EBOV endemic areas," the authors wrote.
Jan 16 Sci Rep study

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