COVID-19 outbreaks among crew members in non-cruise vessels anchoring in Salvador, Brazil, 2021

BACKGROUND The coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has affected the maritime sector due to virus transmission onboard and traffic restrictions. However, reports of SARS-CoV-2 transmission on board have been mostly restricted to those occurring on cruise ships. OBJECTIVES To report COVID-19 outbreaks in eight non-cruise vessels and discuss measures to prevent and control the onboard transmission of SARS-CoV-2. METHODS We investigated outbreaks of COVID-19 on vessels anchoring in Baía de Todos-os-Santos, Salvador, Brazil, between February and November 2021. FINDINGS Most vessels were cargo ships that had docked several times before anchoring in Salvador (five had docked in ≥ 9 ports). The crew ranged from 22 to 63 members. The infection attack rate on each vessel ranged from 9.7 to 88.9%. The risk of symptomatic infection largely varied among the crew of each vessel (0 to 91.6%). Overall, the risk of developing COVID-19 signs and symptoms was lower among crew members vaccinated (age-adjusted risk ratio: 0.19; 95% confidence interval 0.06-0.65). SARS-CoV-2 variants not previously identified in Salvador were detected (C.14, B.1.617.2 and B.1.351). MAIN CONCLUSIONS Despite maritime guidelines to avert COVID-19 on board, outbreaks have happened. The multiple stopovers of non-cruise vessels during their routes may contribute to the spread of SARS-CoV-2 variants worldwide. Reducing the onboard transmission of SARS-CoV-2 depends on joint efforts by the crew and local health authorities and, equally important, achieving high vaccination coverage to prevent infections and illness.

Construction and characterization of a recombinant yellow fever virus stably expressing Gaussia luciferase

ABSTRACT Yellow fever is an arthropod-borne viral disease that still poses high public health concerns, despite the availability of an effective vaccine. The development of recombinant viruses is of utmost importance for several types of studies, such as those aimed to dissect virus-host interactions and to search for novel antiviral strategies. Moreover, recombinant viruses expressing reporter genes may greatly facilitate these studies. Here, we report the construction of a recombinant yellow fever virus (YFV) expressing Gaussia luciferase (GLuc) (YFV-GLuc). We show, through RT-PCR, sequencing and measurement of GLuc activity, that stability of the heterologous gene was maintained after six passages. Furthermore, a direct association between GLuc expression and viral replication was observed (r2=0.9967), indicating that measurement of GLuc activity may be used to assess viral replication in different applications. In addition, we evaluated the use of the recombinant virus in an antiviral assay with recombinant human alfa-2b interferon. A 60% inhibition of GLuc expression was observed in cells infected with YFV-GLuc and incubated with IFN alfa-2b. Previously tested on YFV inhibition by plaque assays indicated a similar fold-decrease in viral replication. These results are valuable as they show the stability of YFV-GLuc and one of several possible applications of this construct.

Full-length infectious clone of a low passage dengue virus serotype 2 from Brazil

Full-length dengue virus (DENV) cDNA clones are an invaluable tool for many studies, including those on the development of attenuated or chimeric vaccines and on host-virus interactions. Furthermore, the importance of low passage DENV infectious clones should be highlighted, as these may harbour critical and unique strain-specific viral components from field-circulating isolates. The successful construction of a functional Brazilian low passage DENV serotype 2 full-length clone through homologous recombination reported here supports the use of a strategy that has been shown to be highly useful by our group for the development of flavivirus infectious clones and replicons.

High prevalence and lack of diversity of Wolbachia pipientis in Aedes albopictus populations from Northeast Brazil

The use of Wolbachia as a tool to control insect vectors has recently been suggested. In this context, studies on the prevalence and diversity of this bacterium in wild populations are relevant. Here, we evaluated the diversity of two Wolbachiagenes (ftsZ and wsp) and the prevalence of this endosymbiont in wild Aedes albopictus. Using semi-nested polymerase chain reaction, our results showed that 99.3 percent of the individuals were superinfected with Wolbachia. In regards to genetic diversity, the two genes showed no variation within or among mosquito populations. An analysis of other Wolbachia markers may help to clarify the relationship between insect and endosymbiont.