Figure 1: In addition to influenza and rhinoviruses, human coronaviruses are currently circulating in Germany (as of January 2025).
Most respiratory viruses circulate during the cooler seasons, which coincides with increased numbers of respiratory illnesses. But which viruses are currently predominant, what characterises these pathogens and how are they transmitted? This article answers these and many other questions about influenza and common cold viruses. At the end you will also learn what you can do yourself to prevent infections or treat them naturally.
Overview: Respiratory viruses and their main characteristics
If, like most people, you have had influenza or a cold several times in your life, you will probably know how differently the illnesses can present. The course and severity largely depend on which virus is responsible for the infection. Overall, more than 200 different respiratory viruses are known to cause respiratory disease. In Germany, since week 1 of 2025 infections with rhinoviruses have been recorded most frequently, followed by seasonal human coronaviruses and influenza viruses.[1] Below we present these and other viruses with their key properties.
Influenza virus
Influenza viruses are found worldwide and occur mainly during seasonal influenza waves in the winter months in both the northern and southern hemispheres. In Germany, influenza virus infections typically increase markedly in January or February.[2] The influenza pathogens belong to the so-called Orthomyxoviridae and can be divided into different types (A–D). Influenza A and B are particularly relevant for humans, with influenza A responsible for most seasonal flu epidemics and pandemics. Some influenza viruses can infect not only humans but also birds, pigs, horses or cattle.
Transmission usually occurs via droplet infection when speaking, coughing or sneezing. Contact transmission, for example through handshakes or touching contaminated surfaces, is also possible. Typical symptoms of influenza include sudden onset of illness as well as fever, sore throat, cough, chills, muscle aches and headaches. Depending on overall health and the possible occurrence of complications (e.g. pneumonia, cardiovascular problems), the duration of illness averages 5 to 7 days.
Rhinovirus
According to epidemiological studies, rhinoviruses are the most common cause of colds in humans.[3] These viruses circulate mainly in transitional seasons (spring and autumn). Because there are many subgroups (serotypes) of rhinoviruses, immunity to all types is not possible, which explains the high rate of reinfection. Rhinoviruses belong to the Picornaviridae family. They can be transmitted both by droplets and by contact, and have an incubation period of 1 to 3 days.
As the word “rhino” (Greek: nose) in the name of these RNA viruses suggests, rhinoviruses primarily infect the upper respiratory tract. They bind to receptors on the mucosal cells of the airways, then enter the cell and use the cell’s structures to produce more virus. The accompanying symptoms of a rhinovirus infection are typical cold symptoms such as nasal congestion or runny nose, cough, sore throat, sneezing, headaches and general fatigue. These symptoms usually last 7 to 10 days.
Avian influenza virus
The avian influenza (AI), colloquially known as bird flu or fowl plague, has so far been detected mainly in chickens and turkeys. Cases have also been reported in swans, dairy cows and in humans. However, no human case of avian influenza has yet been recorded in Germany. The Robert Koch Institute (RKI) assesses the risk of avian influenza viruses posing a danger to humans in Europe/Germany as generally low. The RKI does not rule out the possibility that avian influenza viruses could adapt genetically so that person-to-person transmission becomes possible.[4]
Highly pathogenic avian influenza viruses (e.g. H5N1) spread rapidly and can cause mass die-offs in wild and domestic birds. Infected birds suffer severe symptoms such as neurological disorders or fatal organ failure. The virus can be transmitted from animal to animal, via the air, or indirectly via contaminated clothing and feed on poultry farms.
Human coronavirus (hCoV) and SARS‑CoV‑2
The virus SARS‑CoV‑2 became globally known with the coronavirus pandemic that began in 2019. On 5 May 2023 the WHO declared that COVID‑19 no longer constituted a “public health emergency of international concern”.[5] Nevertheless, coronaviruses continue to circulate here as well. The group of human coronaviruses is widespread and is mainly responsible for mild respiratory infections with minor cold symptoms such as a runny nose, cough and sore throat. SARS‑CoV‑2 is different: this betacoronavirus is highly pathogenic and can cause severe respiratory disease. Possible symptoms include fever, shortness of breath, loss of smell and taste, and pneumonia. Transmission of SARS‑CoV‑2 can easily occur via droplet and contact infection or via aerosols. In addition, SARS‑CoV‑2 has produced numerous mutations (e.g. Alpha, Delta, Omicron).
Respiratory syncytial virus (RSV)
Infections with respiratory syncytial virus (RSV) typically occur more frequently between October and March. The most common mode of transmission is droplet infection. Depending on age, health status and severity of infection, RSV can cause mild upper respiratory infections or severe lower respiratory disease. Common mild symptoms include nasal congestion, cough, mild fever, sore throat and reduced appetite. Severe RSV infections can lead, among other things, to marked shortness of breath, otitis media and pneumonia and, due to lack of oxygen, a bluish discolouration of the skin (cyanosis). Risk groups for severe courses include especially premature infants and babies with certain underlying conditions, as well as adults aged 75 and over and older adults with underlying diseases.
Human metapneumovirus (hMPV)
Human metapneumovirus (hMPV) is closely related to RSV. First discovered in 2001, the pathogen also occurs worldwide but less frequently than RSV. Symptoms of an hMPV infection are often somewhat milder. Infants, toddlers, older people and immunocompromised persons are particularly at risk. At the beginning of 2025 media reports caused a stir reporting an outbreak of human metapneumovirus in some regions of China. However, the WHO distanced itself from these claims and emphasised that the numbers of acute respiratory infections in China had indeed risen compared with the previous month, but that this represented a normal seasonal development.[6]
Natural measures against infections: the best medicinal plants and home remedies
Figure 2: In naturopathy there are numerous medicinal plants available to treat and prevent respiratory illnesses naturally.
There are a variety of medicinal plants that have antiviral effects and can be used to support treatment of respiratory infections. Naturopathy also places great importance on prevention through comprehensive strengthening of the immune system. The most important antiviral medicinal plants and natural home remedies include:
- Echinacea purpurea: This plant, also known as coneflower, is traditionally used to support the immune system and has proven antiviral and antibacterial properties. A meta-analysis found that Echinacea can reduce the duration of cold symptoms by an average of 1.4 days.[7] It is usually taken as drops, tinctures, lozenges or capsules.
- Grapefruit seed extract: Due to its strong antimicrobial action, grapefruit seed extract is regarded as a natural antibiotic. The extract shows excellent activity not only against viruses and bacteria but can also inhibit the growth of various fungi (e.g. yeasts such as Candida albicans). Orally, grapefruit seed extract is usually taken as drops mixed with a glass of fruit juice or water.
- Elderberries: Both the dark berries and the flowers of the black elder (Sambucus nigra) are rich in valuable nutrients and bioactive compounds. The flavonoids in elder, together with vitamin C, vitamin A and essential oils, provide ideal conditions for cold and flu symptoms to subside more quickly.[8] Caution: elderberries should always be cooked before use, as the compound sambunigrin can otherwise be toxic and cause gastrointestinal complaints.
- Quercetin: The secondary plant compound quercetin also has antiviral and anti-inflammatory properties. The flavonoid, found for example in capers and lovage, can inhibit certain viral enzymes and thus block the replication of cold viruses. Quercetin also makes it harder for pathogens to enter potential host cells and strengthens immune defence by promoting the activity of immune cells. The antiviral effect of quercetin has been confirmed by several scientific studies. Both in vitro and in vivo studies have shown that quercetin is able to inhibit rhinovirus replication.[9] There is also evidence that quercetin can bind to viral proteins and thus reduce the activity of SARS‑CoV‑2.[10]
- Rosemary: Rosemary has been shown in studies to be particularly effective against influenza viruses.[11] The Mediterranean plant contains many valuable essential oils such as cineole, borneol and camphor, which have antibacterial and antiviral effects and can support the body in fighting pathogens. For colds and flu, tea made from dried rosemary leaves, inhalations and baths with rosemary oil are particularly soothing.
- Ginger: Ginger is a true all‑rounder among medicinal plants. The contained gingerol belongs to the polyphenols and is responsible for the typical pungent ginger taste. Gingerol and many other active substances in ginger also have anti-inflammatory and antioxidant effects. The antiviral activity of fresh ginger has been demonstrated in studies, among others, against avian influenza viruses and respiratory syncytial virus (RSV).[12]
Alongside the use of medicinal plants, a healthy lifestyle is an important foundation for preventing viral respiratory diseases. Pay attention to a diet rich in antioxidants, vitamins and minerals. To strengthen your body’s own defences, choose more vitamin C-rich foods such as red peppers and citrus fruits. Regular, moderate exercise (e.g. walks, yoga) benefits the immune system as much as sufficient sleep (7 to 9 hours), adequate fluid intake (at least 1.5 to 2 litres a day, depending on body weight), fresh air and sunlight. You can additionally support your immune system with natural supplements, ideally containing vitamin D and zinc.
Biographical
Katharina Korbach regularly writes blog posts on medicinal plants and natural active ingredients for the Narayana Verlag. She became interested in language early on and began writing her own literary texts. A serious illness during her school final exams led to an intensive engagement with health and nutrition topics that continues to this day. After repeated failure of conventional medical treatments, she chose a more self‑effective, naturopathic treatment approach. A plant‑based diet was a key element of her recovery.
Katharina studied Cultural Studies (B.A.) and Applied Literary Studies (M.A.). In 2022 she published her debut novel “Sperling” with Berlin Verlag. She now lives in Berlin as a freelance author, medical editor and lecturer. In her free time she prefers to spend time with friends or at barre training. She also loves travelling and trying out new vegan recipes.
[1] RKI (2025): GrippeWEb weekly report, calendar week 3/2025. https://www.rki.de/DE/Content/Infekt/Sentinel/Grippeweb/grippeweb_ergebnisse_node.html (accessed: 22.01.2024).
[2] RKI (2018): Influenza (Part 1): Diseases caused by seasonal influenza viruses. https://www.rki.de/DE/Content/Infekt/EpidBull/Merkblaetter/Ratgeber_Influenza_saisonal.html (accessed: 22.01.2025).
[3] Wat D. The common cold: a review of the literature. Eur J Intern Med. 2004 Apr. https://pubmed.ncbi.nlm.nih.gov/15172021/.
[4] RKI (2024): RKI on human cases of avian influenza (bird flu). https://www.rki.de/DE/Content/InfAZ/Z/ZoonotischeInfluenza/Vogelgrippe.html (accessed: 22.01.2025).
[5] WHO (2023): Statement on the fifteenth meeting of the IHR (2005) Emergency Committee on the COVID‑19 pandemic. https://www.who.int/news/item/05-05-2023-statement-on-the-fifteenth-meeting-of-the-international-health-regulations-(2005)-emergency-committee-regarding-the-coronavirus-disease-(covid-19)-pandemic (accessed: 24.01.2025).
[6] Deutsches Ärzteblatt (2025): WHO cannot confirm reports of an outbreak of human metapneumovirus in China. https://www.aerzteblatt.de/nachrichten/156741/WHO-kann-Berichte-zu-Ausbruch-mit-humanem-Metapneumovirus-in-China-nicht-bestaetigen (accessed: 24.01.2025).
[7] Shah SA, Sander S, White CM, Rinaldi M, Coleman CI. Evaluation of echinacea for the prevention and treatment of the common cold: a meta-analysis. Lancet Infect Dis. 2007 Jul. https://pubmed.ncbi.nlm.nih.gov/17597571/.
[8] Tiralongo E, Wee SS, Lea RA. Elderberry Supplementation Reduces Cold Duration and Symptoms in Air‑Travellers: A Randomized, Double‑Blind Placebo‑Controlled Clinical Trial. Nutrients. 2016 Mar 24. https://pmc.ncbi.nlm.nih.gov/articles/PMC4848651/.
[9] Ganesan S, Faris AN, Comstock AT, Wang Q, Nanua S, Hershenson MB, Sajjan US. Quercetin inhibits rhinovirus replication in vitro and in vivo. Antiviral Res. 2012 Jun. https://pmc.ncbi.nlm.nih.gov/articles/PMC3360794/.
[10] Önal H, Arslan B, Üçüncü Ergun N, Topuz ?, Yilmaz Semerci S, Kurnaz ME, Molu YM, Bozkurt MA, Süner N, Kocata? A. Treatment of COVID‑19 patients with quercetin: a prospective, single centre, randomised, controlled trial. Turk J Biol. 2021 Aug 30. https://pmc.ncbi.nlm.nih.gov/articles/PMC8573830/
[11] Khwaza V, Oyedeji OO, Aderibigbe BA. Antiviral Activities of Oleanolic Acid and Its Analogues. Molecules. 2018 Sep 9. https://pmc.ncbi.nlm.nih.gov/articles/PMC6225463/.
[12] Chang JS, Wang KC, Yeh CF, Shieh DE, Chiang LC. Fresh ginger (Zingiber officinale) has anti‑viral activity against human respiratory syncytial virus in human respiratory tract cell lines. J Ethnopharmacol. 2013 Jan 9. https://pubmed.ncbi.nlm.nih.gov/23123794/.
Figure 1: Drehstrom Filmproduktion/shutterstock.com; Figure 2: Iva Vagnerova/shutterstock.com
03.02.2025
