Several viruses, including those that cause dengue and yellow fever, can impair coagulation, leading to bleeding in the most severe cases. For this reason, these conditions are considered hemorrhagic viral fevers. In a paper recently published in the scientific journal Memórias do Instituto Oswaldo Cruz, a group of ten researchers argues that the new coronavirus (Sars-CoV-2) should be the first agent recognized for acting in the opposite direction: increasing the formation of clots (also called thrombi) that can obstruct circulation. Considering the evidence of hypercoagulation in the disease, the authors propose that Covid-19 is the first infection classified as thrombotic viral fever. The condition is currently classified as Severe Acute Respiratory Syndrome (SARS).
The trial is signed by specialists in intensive care, cardiology, hematology, virology, pathology, immunology and molecular biology, who work in six health care and scientific research institutions in Brazil. They are: Hospital Pró-Cardíaco, Oswaldo Cruz Institute (IOC/Fiocruz), Faculdade de Medicina de Petrópolis (Unifase), National Cancer Institute (Inca), Carlos Chagas Institute (Fiocruz Paraná), and United Health Group. The Comparative and Environmental Virology, the AIDS and Molecular Immunology, the Inflammation, the Pathology and Immunopharmacology Laboratories participate at the IOC/Fiocruz.
Scientific evidence
Almost a year after the emergence of the new coronavirus in China, several studies demonstrate that, contrary to what was thought at the beginning of the pandemic, Covid-19 goes far beyond pulmonary conditions. In the Netherlands, a survey identified complications related to excessive clot formation in 16% of patients in intensive care units, including cases of pulmonary embolism, stroke and venous thrombosis. In a French survey, the index went over 40%. In addition, in people who died from the infection, analyzes found significant damage to the endothelium, tissue that lines blood vessels. Research indicates that Sars-CoV-2 infects endothelial cells, and tissue inflammation favors a state of hypercoagulation.
“In hospitalized patients, we see thrombotic manifestations in spite of the usual clinical practice of thromboprophylaxis [therapy to prevent the formation of clots]. There is also a description of thromboembolic events after hospital discharge, and excessive clot formation is observed in histopathological analyzes in cases of death by Covid-19”, says the ICU coordinator at Hospital Pró-Cardíaco and first author of the paper, Rubens Costa Filho.
For the authors of the paper, the classification of thrombotic viral fever reflects the advance in knowledge about the disease and may contribute to the clinical management of cases and scientific research. "This definition highlights the need for measures to monitor and treat coagulation alterations and points to issues that need to be clarified, such as the identification of biomarkers of severity, which can be used to guide therapeutic approaches", says the researcher of the Comparative and Environmental Virology Laboratory at IOC and senior author of the study, José Paulo Gagliardi Leite.
The researchers also explain that the change in classification would not impact the current monitoring systems that contribute so much to the definition of public health strategies. “SARS is a nomenclature used to portray a nonspecific clinical involvement, since it can cover a series of manifestations. Thrombotic viral fever, on the other hand, would represent a specific syndrome. This definition is fundamental in the Health area”, stresses Costa Filho.
