Research for infection protection

Noroviruses, influenza viruses & co: what you should pay attention to during the coming autumn and winter of the pandemic

In light of decreasing temperatures and rising numbers of SARS-CoV-2 cases, most people are concerned about the upcoming months. COVID-19, influenza, or simply the common flu – who can correctly distinguish between the partly overlapping symptoms, especially in the early stages? Additionally, the routes of transmission of SARS-CoV-2, influenza viruses, and many other respiratory pathogens closely resemble each other. In principle, they can all be transmitted through droplets, aerosols and contact infection. Only the particle size is different – consequently, the behaviour of the aerosols also differs. This means, however, that the current hygiene measures and rules of conduct during the COVID-19 pandemic also have an impact on the transmission of influenza viruses and other respiratory pathogens.


Noroviruses: Symptoms and transmission routes are significantly different from those of respiratory pathogens

Noroviruses, which are the triggers of highly contagious gastroenteritis, are conversely transmitted through the stool and vomit of the ill, mostly faecally-orally or orally (e.g., through hand contact with contaminated surfaces or oral ingestion of droplets contaminated with the virus, as a result of projectile vomiting). However, contaminated foods and beverages are also possible sources of transmission. The transmission routes of the noroviruses thus differ significantly from those of the respiratory pathogens. Diarrhoea and vomiting are most common when it comes to symptoms, allowing this illness to be clearly distinguished from other seasonal infections. Even though diarrhoea can occur as another symptom in COVID cases, severe gastrointestinal symptoms are otherwise quite rare. A transmission of SARS-CoV-2 through excretion is considered unlikely, according to current research. Since 10-100 virus particles are enough to cause a norovirus infection, the virus can spread rapidly in facilities with many people (e.g. nursing homes, hospitals, and shared facilities) and often occurs seasonally, like influenza and the common flu.


Will different viral infections coincide with and rife alongside the pandemic in the coming season?

While we are dealing with SARS-CoV-2, a new and only moderately researched pathogen, we also have decades of experience with other pathogens and their seasonal courses. The website of the Working Group Influenza (Arbeitsgemeinschaft Influenza, AGI), part of the Robert Koch Institute, shows reports on the course of the seasonal influenza wave since the mid-1990s. The AGI works in Germany, monitoring the seasonal activity of respiratory infections in general and influenza in particular, as well as evaluates the results. Therefore, it is also known that the first influenza cases usually happen in autumn, with an expected increase in cases only at the turn of the year or shortly after. Moreover, all samples that are sent in and part of the AGI are tested for additional viruses as well – for respiratory syncytial viruses, adeno-, rhino-, and human metapneumoviruses, that is. Thus, the seasonal course of these infections can be quite accurately assessed, too. When looking at and comparing the graphs of the seasonal course of different pathogens (here in the seasonal report of 2018/19, for example), it is evident that the rhinoviruses are very prevalent already in late September/early October, and that the spread of the virus clearly decreases until the end of the year. In a typical year, the peak times of influenza viruses and rhinoviruses barely overlap at all. Nevertheless, it is currently unclear how the course of these viruses will develop during the COVID-19 pandemic.


Basic hygiene is the foundation for protection against ALL seasonal infections

A runny nose, a slightly sore throat – a cold or COVID-19? Only laboratory testing can provide absolute certainty in cases of unclear symptoms. At the beginning of October (week 41), rhinoviruses were found in 25 of the 49 submitted sentinel samples, and SARS-CoV-2 was found in 3 of the 47 examined samples at the German National Reference Center (NRZ) for influenza viruses, while influenza viruses were not found in any of the examined samples. Since prevention always is better than cure, one should ensure adequate basic hygiene everywhere – in addition to further protective measures – so that infections and the consequent uncertainty can be avoided in the first place. Effective hand hygiene is the foundation of protection against ALL these infections. In the short video Hand hygiene in healthcare, we show you what you should pay special attention to.


Sources:
1. Robert Koch-Institut: SARS-CoV-2 Steckbrief zur Coronavirus-Krankheit-2019 (COVID-19).
2. Robert Koch-Institut: Influenza (Teil 1): Erkrankungen durch saisonale Influenzaviren.
3. de Gabory L, et al. The influenza virus, SARS-CoV-2, and the airways: Clarification for the otorhinolaryngologist. Eur Ann Otorhinolaryngol Head Neck Dis 2020; 137: 291–296.
4. Fennelly KP. Particle sizes of infectious aerosols: implications for infection control. Lancet Respir Med 2020; 8: 914–924.
5. Robert Koch-Institut: Ratgeber Norovirus-Gastroenteritis.
6. Jones DL, et al. Shedding of SARS-CoV-2 in feces and urine and its potential role in person-to-person transmission and the environment-based spread of COVID-19. Sci Total Environ 2020; 749: 141364.
7. Robert Koch-Institut, Arbeitsgemeinschaft Influenza: Bericht zur Epidemiologie der Influenza in Deutschland Saison 2018/19.
8. Robert Koch-Institut, Arbeitsgemeinschaft Influenza: Influenza-Wochenbericht Kalenderwoche 41 2020.