# Amazon tropical fishes of commercial interest show human-cell contamination but no SARS-CoV-2 in a real-life scenario

## TL;DR

A study in the Amazon found no SARS-CoV-2 in tropical fish or their environments, but detected human genetic material, suggesting human contamination.

## Contribution

Demonstrates absence of SARS-CoV-2 in fish and wastewater, while highlighting human pathogen presence in market environments.

## Key findings

- SARS-CoV-2 was not detected in fish, aerosols, or wastewater samples.
- Human RP gene was detected in 181 fish samples, indicating human contamination.
- High levels of human genetic material suggest potential for human pathogen transmission in these markets.

## Abstract

Amazonas was one of the most impacted Brazilian states by the COVID-19 pandemic. Mortality rates were high, and the health systems collapsed. It is important to identify possible intermediate reservoirs to avoid animal-to-human contamination. Several tropical fish are of commercial interest and are sold in large open-air markets in the region, representing a large economic and dietary importance.

This study aimed to verify if fish species of commercial importance, aerosols, and fish wastewater in local open-air markets, at a major capital city in the western Brazilian Amazon, are contaminated by SARS-CoV-2.

488 fish, 50 aerosol, and 45 wastewater samples were analyzed for the presence of SARS-CoV-2. The samples were subjected to extraction using the BIOGENE Viral DNA/RNA Extraction kit, and the molecular diagnosis was tested for SARS-CoV-2 using the Bio-Manguinhos SARS-CoV-2 (EDx) Molecular Kit.

It was not possible to detect the virus (Ct≤40, for Gene E) in these samples, however, in 181 samples of fish it was possible to detect the human RP gene (Ct≤35, for the RP Gene), indicating human contact. There was a high number of COVID-19 diagnoses in all city districts in which the samples were collected, showing that SARS-CoV-2 was circulating.

This study indicates that fish of local commercial importance do not carry SARS-CoV-2 viral particles, despite circulation of SARS-CoV-2, and are not an important source of animal-to-human contamination. Despite these results, the human RP gene was found detectable in fish, air, and fish wastewater, showing that such places may carry human pathogens.