Science and Technology

Wastewater Analysis: Técnico researchers track the spread of a virus like the one that causes dengue fever

The method makes it possible to detect viruses in wastewater before they spread further into the population.

Técnico researchers analysed wastewater samples from various parts of the country for the presence of the dengue and chikungunya viruses, which are spread through mosquito bites. The study, published in Lancet Microbe, involves the participation of Sílvia Monteiro and Ricardo Santos, researchers at Técnico Water Testing Laboratory (LAIST), Civil Engineering Research and Innovation for Sustainability (CERIS), and the Department of Engineering and Nuclear Sciences (DECN), and Filipa Nunes, a PhD student at the Técnico.

Of the 273 samples tested, 25% contained a viral load of dengue and 11% of chikungunya. However, no autochthonous cases of these diseases had been detected in Portugal. All known cases were linked to travellers.

Wastewater allows to observe the circulation of viruses in the community, including non-resident populations that may be infected, thus increasing the potential for Aedes albopictus mosquitoes to come into contact with dengue or chikungunya, which increases the likelihood of autochthonous cases. The technique for detecting arboviruses and other targets in wastewater makes it possible to visualise the circulation of diseases almost in real time, regardless of the development of symptoms, unlike clinical surveillance, which depends on the manifestation of symptoms.

In this study, it was possible to detect the dengue virus in wastewater, which is in line with the data reported by Portugal to the European Centre for Disease Prevention and Control (ECDC). It was also possible to verify the circulation of the chikungunya virus in the country, which had not been identified by clinical surveillance. The technique can also be used in airports and aircraft to monitor the presence of these diseases in passengers arriving in our country, allowing measures to be implemented to prevent their introduction into Portugal.

Not used in Portugal on a regular basis, wastewater monitoring is able to collect information on the spread of viruses without depending on the appearance of symptoms of illness. “By collecting and analysing these wastewaters, we can ‘see’ what is happening to the population’s health. For example, if a new virus is spreading among the population, it can be detected in wastewater before it spreads further among several people. This allows health authorities to act quickly, taking measures to control the spread of the virus”, explains Sílvia Monteiro. ‘It’s a smart and efficient way of monitoring public health without having to test each person individually,’ she adds.

“Wastewater monitoring is not intended to replace clinical surveillance, but rather to complement it”, says Ricardo Santos. “This method has certain advantages, such as the ability to assess an entire population served by a given treatment plant, non-invasive technique, high sensitivity method, and the possibility of monitoring disease trends more quickly and in a more economical way than clinical surveillance.

In the article, the researchers point to climate change as an aspect that could facilitate the geographical dispersion of the insects that spread these viruses, making this type of diagnosis even more relevant as an epidemiological screening tool in Portugal. Several European countries such as the Netherlands, Spain and Italy, as well as the United States, Canada, New Zealand and Australia have implemented programmes to monitor microorganisms and, consequently, diseases circulating in the population.

LAIST has extensive experience in monitoring wastewater for antibiotic resistance genes, antibiotic-resistant bacteria, enteric viruses, and SARS-CoV-2. For over 100 years, LAIST has been characterising and monitoring the quality of water used for various purposes, including public supply, irrigation, and industry. LAIST also has a strong scientific research component that supports its area of activity.