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Web search tools are widely used by the general public to obtain health-related information, and analysis of search data is often suggested for public health monitoring. We analyzed popularity of searches related to smell loss and taste loss, recently listed as symptoms of COVID-19. Searches on sight loss and hearing loss, which are not considered as COVID-19 symptoms, were used as control. Google Trends results per region in Italy or state in the US were compared to COVID-19 incidence in the corresponding geographical areas. The COVID-19 incidence did not correlate with searches for non-symptoms, but in some weeks had high correlation with taste and smell loss searches, which also correlated with each other. Correlation of the sensory symptoms with new COVID-19 cases for each country as a whole was high at some time points, but decreased (Italy) or dramatically fluctuated over time (US). Smell loss searches correlated with the incidence of media reports in the US. Our results show that popularity of symptom searches is not reliable for pandemic monitoring. Awareness of this limitation is important during the COVID-19 pandemic, which continues to spread and to exhibit new clinical manifestations, and for potential future health threats.

Background: Clinical diagnosis of COVID-19 poses an enormous challenge to early detection and prevention of COVID-19, which is of crucial importance for pandemic containment. Cases of COVID-19 may be hard to distinguish clinically from other acute viral diseases, resulting in an overwhelming load of laboratory screening. Sudden onset of taste and smell loss emerge as hallmark of COVID-19. The optimal ways for including these symptoms in the screening of suspected COVID-19 patients should now be established. Methods: We performed a case-control study on patients that were PCR-tested for COVID-19 (112 positive and 112 negative participants), recruited during the first wave (March 2020 - May 2020) of COVID-19 pandemic in Israel. Patients were interviewed by phone regarding their symptoms and medical history and were asked to rate their olfactory and gustatory ability before and during their illness on a 1-10 scale. Prevalence and degrees of symptoms were calculated, and odds ratios were estimated. Symptoms-based logistic-regression classifiers were constructed and evaluated on a hold-out set. Results: Changes in smell and taste occurred in 68% (95% CI 60%-76%) and 72% (64%-80%), of positive patients, with 24 (11-53 range) and 12 (6-23) respective odds ratios. The ability to smell was decreased by 0.5 ± 1.5 in negatives, and by 4.5 ± 3.6 in positives, and to taste by 0.4 ± 1.5 and 4.9 ± 3.8, respectively (mean ± SD). A penalized logistic regression classifier based on 5 symptoms (degree of smell change, muscle ache, lack of appetite, fever, and a negatively contributing sore throat), has 66% sensitivity, 97% specificity and an area under the ROC curve of 0.83 (AUC) on a hold-out set. A classifier based on degree of smell change only is almost as good, with 66% sensitivity, 97% specificity and 0.81 AUC. Under the assumption of 8% positives among those tested, the predictive positive value (PPV) of this classifier is 0.68 and negative predictive value (NPV) is 0.97. Conclusions: Self-reported quantitative olfactory changes, either alone or combined with other symptoms, provide a specific and powerful tool for clinical diagnosis of COVID-19. The applicability of this tool for prioritizing COVID-19 laboratory testing is facilitated by a simple calculator presented here.

Background Clinical diagnosis of COVID-19 is essential for detection and prevention of COVID-19. Sudden onset of taste and smell loss is a hallmark of COVID-19, and optimal ways for including these symptoms in the screening of patients and distinguishing COVID-19 from other acute viral diseases, should be established. Methods We performed a case-control study on patients that were PCR-tested for COVID-19 (112 positive and 112 negative participants), recruited during the first wave (March 2020 – May 2020) of COVID-19 pandemic in Israel. Patients reported over by phone their symptoms and medical history and rated their olfactory and gustatory abilities before and during their illness on a 1-10 scale. Results Changes in smell and taste occurred in 68% (95% CI 60%-76%) and 72% (64%-80%), of positive patients, with 24 (11-53 range) and 12 (6-23) respective odds ratios. The ability to smell was decreased by 0.5±1.5 in negatives, and by 4.5±3.6 in positives. A penalized logistic regression classifier based on 5 symptoms has 66% sensitivity, 97% specificity and an area under the ROC curve of 0.83 (AUC) on a hold-out set. A classifier based on degree of smell change only is almost as good, with 66% sensitivity, 97% specificity and 0.81 AUC. The predictive positive value (PPV) of this classifier is 0.68 and negative predictive value (NPV) is 0.97. Conclusions Self-reported quantitative olfactory changes, either alone or combined with other symptoms, provide a specific tool for clinical diagnosis of COVID-19. A simple calculator for prioritizing COVID-19 laboratory testing is presented here.

Objectives: The multifaceted disease manifestation of COVID-19 requires longitudinal characterization of symptoms, to aid with screening and disease management. Methods: Phone interviews and follow-ups were completed with 112 mild COVID-19 RT-PCR-positive adult patients, over a 6 week period. Results: More than one symptom at disease onset was experienced by ~70 of the patients. Over one third of patients experienced fever, dry cough, headache, or muscle ache as the first symptom. If fatigue was reported, it was usually the first symptom to appear. Smell and taste changes had occurred 3.9 ± 5.4 and 4.6 ± 5.7 days (mean ± SD) since disease onset and emerged as first symptoms in 15% and 18% of patients, respectively. Fever was the shortest lasting symptom (5.8 ± 8.6 days (mean ± SD), and smell and taste changes were the most long-lasting symptoms (24.3 ± 22.9 days and 19.4 ± 19.1 (mean ± SD), respectively), with longer smell recovery correlated with smell change severity. In one third of patients who reported cough, smell and taste changes, these symptoms persisted after negative RT-PCR tests. Conclusions: Each symptom can occur as first or later, though some are more likely to appear as firsts, and typically more than one symptom occurs at disease onset. The severity of olfactory change is associated with its recovery time. Lack of chemosensory recuperation in recovered patients is common. These findings can aid patients through their illness and provide expected recovery patterns.

Web tools are widely used among population to obtain health related information, and these data are often employed for public health monitoring. Here we analyzed searches related to smell loss and taste loss, recently linked to COVID-19, as well as sight loss and hearing loss, not included in the COVID-19 symptoms list. Google Trends results per region (Italy) or state (United States) over several weeks were compared to the number of new cases prevalence in that geographical area. Taste and smell loss searches were correlated with each other, and, during a limited time window, with new COVID-19 cases. However, this correlation decreased with time, attributable, at least in part, to media coverage. As new symptoms are being discovered for COVID-19 and the pandemic continues to spread around the globe, the lesson learned here, that correlation between public interest in novel symptoms of infectious disease has an initial spike (the "surprise rise") and subsequently goes to a new baseline due to "knowledge saturation", is of general and practical value for the public.Supplementary Figure S1 repeats the calculation presented in Figure 1 for the 22-28 April week. This clearly illustrates the current lack of correlation between the number of new cases in each region (Italy) or state (US) and the popularity of Google searches on either taste or smell loss.

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Sweet taste is innately appealing, ensuring that mammals are attracted to the sweetness of mother’s milk and other sources of carbohydrates and calories. In the modern world, the availability of sugars and sweeteners and the eagerness of the food industry to maximize palatability, result in an abundance of sweet food products, which poses a major health challenge. The aim of the current study is to analyze sweetness levels, liking, and ingredients of online reviews of food products, in order to obtain insights into sensory nutrition and to identify new opportunities for reconciling the palatability–healthiness tension. We collected over 200,000 reviews of ~30,000 products on Amazon dated from 2002 to 2012 and ~350,000 reviews of ~2400 products on iHerb from 2006 to 2021. The reviews were classified and analyzed using manual curation, natural language processing, and machine learning. In total, ~32,000 (Amazon) and ~29,000 (iHerb) of these reviews mention sweetness, with 2200 and 4600 reviews referring to the purchased products as oversweet. Oversweet reviews were dispersed among consumers. Products that included sucralose had more oversweet reviews than average. 26 products had at least 50 reviews for which at least 10% were oversweet. For these products, the average liking by consumers reporting oversweetness was significantly lower (by 0.9 stars on average on a 1 to 5 stars scale) than by the rest of the consumers. In summary, oversweetness appears in 7–16% of the sweetness-related reviews and is less liked, which suggests an opportunity for customized products with reduced sweetness. These products will be simultaneously healthier and tastier for a substantial subgroup of customers and will benefit the manufacturer by expanding the products’ target audience. Analysis of consumers’ reviews of marketed food products offers new ways to obtain informative sensory data.