Background: There is growing concern about individuals reported to suffer repeat COVID-19 disease episodes, these in a small number of cases characterised as de novo infections with distinct sequences, indicative of insufficient protective immunity even in the short term. Methods: Observational case series and case-control studies reporting 33 cases of recurrent, symptomatic, qRT-PCR positive COVID-19. Recurrent disease was defined as symptomatic recurrence after symptom-free clinical recovery, with release from isolation > 14 days from the beginning of symptoms confirmed by qRT-PCR. The case control study-design compared this group of patients with a control group of 62 patients randomly selected from the same COVID-19 database. Results: Of 33 recurrent COVID-19 patients, 26 were female and 30 were HCW. Mean time to recurrence was 50.5 days which was associated with being a HCW (OR 36.4 (p < 0.0 0 01)), and blood type A (OR 4.8 (p = 0.002)). SARS-CoV-2 antibodies were signifcantly lower in recurrent patients after initial COVID-19 (2.4 ± 0.610; p < 0.0 0 01) and after recurrence (6.4 ± 11.34; p = 0.007). Virus genome sequencing identified reinfection by a different isolate in one patient. Conclusions: This is the first detailed case series showing COVID-19 recurrence with qRT-PCR positivity. For one individual detection of phylogenetically distinct genomic sequences in the first and second episodes confirmed bona fide renfection, but in most cases the data do not formally distinguish between reinfection and re-emergence of a chronic infection reservoir. These episodes were significantly associated with reduced Ab response during initial disease and argue the need for ongoing vigilance without an assumption of protection after a first episode.

A variety of viral infections are associated with hypercoagulable states and may be linked to the development of deep venous thrombosis and pulmonary embolism. The Zika and Chikungunya viral infections spread through the South and Central American continents, moving to North America in 2016, with severe cases of polyarthralgia, fever, and Guillain-Barré syndrome leading eventually to death. A decreased trend for both infections was reported in the first quarter of 2017. In this article, we report the possible association of venous thromboembolic events associated with Zika infection. After 2 cases of deep venous thrombosis in patients with acute Zika infections, D-dimer levels were measured in 172 consecutive patients who presented to the emergency department of a university hospital in an endemic region of Brazil with either Zika or Chikungunya infections confirmed by polymerase chain reaction tests. D-dimer levels were increased in 19.4% of 31 patients with Zika and in 63.8% of 141 patients with Chikungunya infections. The mechanisms behind this association are yet to be elucidated as well as the potential for venous thromboembolism prevention strategies for in-hospital patients affected by Zika and Chikungunya infections.

Congenital Zika syndrome (CZS) is a cluster of malformation, and the mechanisms that lead it are still unclear. Using hypothesis-driven candidate genes and their function in viral infections, single-nucleotide polymorphisms (SNPs) were genotyped by quantitative polymerase chain reaction in a sample population from Sergipe State, Brazil. This study shows that rs3775291 SNP at Toll-like receptor 3, which triggers type I interferon antiviral responses in mothers infected by Zika virus during pregnancy, is associated with CZS occurrence (odds ratio [OR], 2.19; 95% confidence interval [CI], 1.158–4.148). Moreover, rs1799964 SNP at tumor necrosis factor-α gene in CZS babies is associated with severe microcephaly (OR, 2.63; 95% CI, 1.13–6.21).

The largest ever recorded epidemic of the Chikungunya virus (CHIKV) broke out in 2004 and affected four continents. Acute symptomatic infections are typically associated with the onset of fever and often debilitating polyarthralgia/polyarthritis. In this study, a systems biology approach was adopted to analyze the blood transcriptomes of adults acutely infected with the CHIKV. Gene signatures that were associated with viral RNA levels and the onset of symptoms were identified. Among these genes, the putative role of the Eukaryotic Initiation Factor (eIF) family genes and apolipoprotein B mRNA editing catalytic polypeptide-like (APOBEC3A) in the CHIKV replication process were displayed. We further compared these signatures with signatures induced by the Dengue virus infection and rheumatoid arthritis. Finally, we demonstrated that the CHIKV in vitro infection of murine bone marrow-derived macrophages induced IL-1 beta production in a mechanism that is significantly dependent on the inflammasome NLRP3 activation. The observations provided valuable insights into virus-host interactions during the acute phase and can be instrumental in the investigation of new and effective therapeutic interventions.

Since March 2020, 11 lineages of severe acute respiratory syndrome coronavirus 2 have been identified in Sergipe state, Northeast Brazil. During the first 6 months of coronavirus disease 2019 (COVID-19) outbreak, there was a higher frequency of B.1 (58.5%) and B.1.1.33 (17.1%) lineages. During the second wave of COVID-19, there was an increased frequency of P.1 (55.6%), the new Brazilian variant of concern.