Minimum Infective Dose of the Major Human Respiratory and Enteric Viruses Transmitted Through Food and the Environment

Abstract

Viruses are a significant cause of morbidity and mortality around the world. Determining the minimum dose of virus particles that can initiate infection, termed the minimum infective dose (MID), is important for the development of risk assessment models in the fields of food and water treatment and the implementation of appropriate infection control strategies in healthcare settings. Both respiratory and enteric viruses can be shed at high titers from infected individuals even when the infection is asymptomatic. Presence of pre-existing antibodies has been shown to affect the infectious dose and to be protective against reinfection for many, but not all viruses. Most respiratory viruses appear to be as infective in humans as in tissue culture. Doses of \1 TCID 50 of influenza virus, rhinovirus, and adenovirus were reported to infect 50% of the tested population. Similarly, low doses of the enteric viruses, norovirus, rotavirus, echovirus, poliovirus, and hepatitis A virus, caused infection in at least some of the volunteers tested. A number of factors may influence viruses' infectivity in experimentally infected human volunteers. These include host and pathogen factors as well as the experimental methodology. As a result, the reported infective doses of human viruses have to be interpreted with caution.

Residual Viral and Bacterial Contamination of Surfaces after Cleaning and Disinfection

“…The data for transfer of microorganisms from contaminated surfaces to the human hand (finger pads) have been determined for rotavirus and hepatitis A virus (1,42) and shown to be approximately 20% after 20 min of drying (1). The number of viruses required for peroral infection is estimated as 10 to 100 infectious particles for rotavirus, norovirus, poliovirus, parechovirus, and influenza A virus (23,32,51,60), and approximately 150 infectious particles for adenovirus (29). An estimated 10 to 100 cells are required for peroral S. Enteritidis infection (49) and S. aureus infection.…”

Application of viability PCR to discriminate the infectivity of hepatitis A virus in food samples

“…Because of this increasing number of HAV outbreaks, it has become even more important to have reliable and widely applicable techniques for the detection and quantification of HAV in food samples (reviewed by Bosch et al, 2011;Sánchez et al, 2007). Moreover, since the infectious dose of enteric viruses is very low (10 to 100 viral particles) (Teunis et al, 2008;Yezli and Otter, 2011), sensitive methods are therefore needed when screening food products for viral pathogens. So far, the current 'gold standard' for the detection of enteric viruses is quantitative reverse transcription PCR (RT-qPCR) but this method cannot discriminate between infectious and inactivated viruses (reviewed by Knight et al, 2013).…”

Population-level effects of suppressing fever

“…This is unsurprising, but estimating the strength of the effect is challenging. A recent review [39] describes 30 studies in which human volunteers were given various doses of a variety of influenza viruses. To analyse these data, we used a binomial generalized linear mixed model incorporating random effects of strain and study [40,41] to estimate the relationship between log 10 (dose) and probability of infection.…”