Viruses transmitted by water and food:
Calicivirus (Norovirus and Sapovirus), Rotavirus, Enterovirus, Hepatitis A, Hepatitis E, Intestinal human Adenovirus and Astrovirus.
Molecular detection by RT-PCR or real-time PCR (Real time-PCR), with or without concentration of virus by filtration
Viruses that can be transmitted through contaminated water or food, are viruses that are eliminated in large numbers with faeces (105 to 1011 viral particles -virions- per gram of faeces) from infected people. This occurs with Calicivirus (Norovirus and Sapovirus), Rotavirus, Enterovirus, Hepatitis A, Hepatitis E, Intestinal human Adenovirus and Astrovirus. Most cause acute gastroenteritis, but others such as hepatitis A virus or hepatitis E cause liver disease.
When eliminated with the feces from infected people in high concentrations, it is the fecal-oral route, through water or food contaminated with them, the predominant mode of transmission. Another route is direct cutaneous-oral contact. These viruses have been found in wastewater, treated wastewater for discharge into surface waters, river waters, marine waters and drinking water from pipes. Contaminated water can contaminate food such as fruits and vegetables. These viruses can remain viable even weeks or months under appropriate environmental conditions.
Outbreaks have occurred even in developed countries with drinking water and wastewater treatment systems, since compliance with bacterial fecal contamination indicators (Escherichia coli or coliforms) does not imply the absence of viable viruses. However, there is sufficient consensus that there is no correlation between the contaminating concentrations of bacteria and viruses in water. On the other hand, very sensitive methods are required to detect the presence of enteric viruses in drinking water or in surface waters, since only 10 particles (virions) of Norovirus are needed to infect a susceptible person. Some of the filtration methods with positively charged membranes to concentrate viruses and elute them later have been criticized because the components used to facilitate membrane concentration or subsequent elution can inhibit molecular detection tests.
Methods performed in IVAMI:
- Virus concentration by membrane filtration and subsequent elution.
- Real-time RT-PCR for viruses with RNA genome, or real-time PCR for viruses with DNA genome, following the guidelines of ISO 15216-2 for hepatitis A and Norovirus viruses.
Types of samples:
- Surface water, wastewater, effluent water from sewage treatment plants: the collection of 5 liters is recommended. The minimum volume of water required is 1 liter.
- Food: the recommended minimum weight for food is 100 grams.
- Bivalve molluscs: sufficient quantity to obtain 20 grams of body mass.
Conservation and shipment of the sample:
- Refrigerated (preferred) for less than 2 days.
- Frozen: more than 2 days.
Delivery of results:
- Real-time RT-PCR and PCR tests: 48 to 72 hours on weekdays.
- RT-PCR and real-time PCR tests, followed by sequencing for typing when required: 4 to 5 working days.
Cost of the test:
- Preparation of water samples or suspensions or food washes, with virus concentration by membrane filtration and virus elution (each sample received): Consult to firstname.lastname@example.org.
- RT-PCR and real-time PCR tests on the virus concentrates eluted from the filtration membranes. Each virus: Consult to email@example.com.
- Molecular typing, when appropriate and requested according to the virus (for example, Caliciviridae to differentiate types of Norovirus and Sapovirus, species of Rotavirus, typing of Enterovirus, genotyping of hepatitis A, Adenovirus species, ...): Consult to firstname.lastname@example.org.