Norovirus Detection Strategies: Evaluating a New Environmental Swabbing Technique

Norovirus is the kind of gastroenteritis that most individuals have experienced and everyone wants to avoid. Commonly called the “cruise ship bug” for its frequent outbreaks aboard commercial cruise ships, this viral infection is highly infectious and thoroughly unpleasant. The Centers for Disease Control and Prevention (CDC) estimates that within the United States, there are 19-21 million cases of acute gastroenteritis every year. Most cases of norovirus are a result of disease transmission between people; however, the virus can also spread through contaminated food, water, and surfaces or objects.

The virus is also problematic for healthcare facilities, as patients in nursing homes or hospitals are the most common source for reported norovirus outbreaks. Whether the virus is introduced into the facility by a patient, visitor, or healthcare worker, it can spread rapidly and do untold damage to patients already experiencing medical ailments. Norovirus is highly contagious and infectious, and being infected once does not provide immunity for future exposures. Individuals are most infectious when they are sick and in the early days of recovery; but, the virus can easily stay in stool for 2 weeks after an individual recovers, which makes the risk of transmission high.

Globally, 1 out of every 5 cases of gastroenteritis is caused by norovirus; leading to roughly 685 million cases worldwide, and an estimated global cost of $60 billion each year. This makes this “stomach bug” extremely taxing both in terms of human morbidity and mortality, and financially.

To combat the spread of the norovirus and its frequent contamination of surfaces and objects, detection is a crucial strategy. To this end, researchers in a new study evaluated different swab-sampling methods that are used to detect norovirus on surfaces. They developed and evaluated a strategy using macrofoam swabs that could detect norovirus on hard surfaces, looking to test the performance of the macrofoam swab for detecting norovirus under field conditions.

The macrofoam protocol, compared to fiber-tipped swabs or antistatic swipes, handled large high-touch surfaces (doorknobs, computers, toilet seats, etc.), which allowed for greater environmental detection. The researchers noted that “we demonstrated that macrofoam swabs, which have a larger swab head than the fiber-tip swabs, have higher recovery rates for human norovirus when sampling environmental surfaces with an area up to 70 cm².”

The protocol involved performing viral extraction from the swab, concentration of the viral RNA using spin columns, genotype detection, quantification of norovirus in the swabs, etc.

In an attempt to provide the most real-world scenarios, the researchers evaluated a series of surfaces and objects that are considered most high-touch: handrails, toilet seats, cruise ship cabin remote controls, faucets, restaurant counter surfaces, etc. Following their work, they noted that “considering the higher recovery efficiency for norovirus of macrofoam swabs over those fibers tipped swabs, [they expected] that the macrofoam swabs will be able to detect other enteric viruses as well.”

This new study evaluating norovirus swab-sampling methods provides not only future recommendations, but also has the potential for more effective environmental analysis during gastroenteritis outbreaks. Environmental microbial burden with such pathogens can be challenging to detect and therefore surveillance is vital during outbreaks to determine control methods. Environmental testing is also crucial to efforts to determine the point-source for the outbreak. Given the global burden of norovirus, this infection preventionist thinks the new protocol has the potential to change the accuracy and rates of detection, and ensure a more rapid response in decontamination to ensure less individuals are affected.