key: cord-1040844-3sbdv2zc authors: Kurita, J.; Sugawara, T.; Ohkusa, Y. title: Effects of climate conditions, mobility trends, and countermeasures on the COVID-19 outbreak in Japan date: 2021-01-04 journal: nan DOI: 10.1101/2020.12.29.20248977 sha: 52e2bf9e5f8e41a648f9eb6a13f3e8a758993288 doc_id: 1040844 cord_uid: 3sbdv2zc Background: As of mid-December the third wave of COVID-19 infection in Japan was larger than the prior two waves. Therefore, the Goto Travel Campaign (GTC) was presumed as the main cause of the third wave. Object: We evaluated GTC effects considering climate conditions and mobility. Method: We regressed R(t) on temperature, humidity, mobility, and countermeasures. Results: Estimation results indicate that temperature was a negative and significant influence; mobility was positive and significant. The emergency state and GTC were negative and significant. Discussion and Conclusion: Estimation results show that R(t) would increase by 0.52 if the temperature were to decline by 20{degrees}C. To cancel this effect, going out should be reduced by 50%. We conclude that GTC did not raise infectiousness. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted January 4, 2021. ; https://doi.org/10.1101/2020.12.29.20248977 doi: medRxiv preprint Introduction As a countermeasure against the COVID-19 outbreak in Japan, an emergency condition was declared on April 7 until the end of May. During this period, the first peak was achieved on April 3. It then reemerged until July 29, as shown in Figure 1 . However, the so-called "Goto Travel Campaign" (GTC) started on July 23 subsidized travel and shopping at tourist destinations which aims to enforce sightseeing business even though it may expand the outbreak. GTC continued to the end of December, by which time the third wave had emerged. The third wave was larger than either of the prior two waves as of mid-December. Therefore, GTC was inferred as the main reason underlying the third However, although results were mixed, some research suggests that COVID-19 might be associated with climate conditions, at least in China [2] [3] [4] . If that were true for Japan, then GTC might not be the main reason for the third wave in Japan. Moreover, mobility was inferred as the main cause of the outbreak dynamics, at least in the first wave in Japan [5] as well as in the world [6] . Therefore, for this study, we evaluate the effects of GTC while considering climate conditions and mobility. The number of symptomatic patients reported by the Ministry of Labour, Health All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted January 4, 2021. ; https://doi.org/10.1101/2020.12.29.20248977 doi: medRxiv preprint and Welfare (MLHW) for January 14 -November 30, published [7] as of December 25 was used. Some patients were excluded from data for Japan: those presumed to be persons infected abroad or infected as Diamond Princess passengers. Those patients were presumed not to represent community-acquired infection in Japan. For onset dates of some symptomatic patients that were unknown, we estimated their onset date from an empirical distribution with duration extending from the onset to the report date among patients for whom the onset date had been reported. The following procedure was similar to that used for our earlier research [8, 9] . We estimated the onset date of patients for whom onset dates were not reported as follows: Letting f(k) represent this empirical distribution and letting N t denote the number of patients for whom onset dates were not available published at date t, then the number of patients for whom the onset date was known is t-1. The number of patients for whom onset dates were not available was estimated as f(1)N t . Similarly, the number of patients with onset date t-2 and for whom onset dates were not available were estimated as f(2)N t . Therefore, the total number of patients for whom the onset date was not available, given an onset date of s, was estimated as Σ k=1 f(k)N s +k for the long duration extending from s. Moreover, the reporting delay for published data from MHLW might be considerable. In other words, if s+k is larger than that in the current period t, then s+k All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted January 4, 2021. ; https://doi.org/10.1101/2020.12.29.20248977 doi: medRxiv preprint represents the future for period t. For that reason, Ns+k is not observable. Such a reporting delay engenders underestimation of the number of patients. For that reason, it must be adjusted as Similarly, patients for whom the onset dates were available are expected to be affected by the reporting delay. Therefore, we where M s |t represents the reported number of patients for whom onset dates were within period s, extending until the current period t. We defined R(t) as the number of the infected patients on day t divided by the number of patients who were presumed to be infectious. The number of infected patients was calculated from the epidemic curve by the onset date using a distribution of the incubation period. The distribution of infectiousness in symptomatic and asymptomatic cases was assumed to be 30% on the onset day, 20% on the following day, and 10% for the subsequent five days [10] . We use average temperature and relative humidity data for Tokyo during the day as climate data. We obtained the data from the Japan Meteorological Agency (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted January 4, 2021. To clarify associations among R(t) and climate, mobility, and countermeasures, we regressed the daily R(t) on daily climate, mobility, and countermeasures. The study period extended from January 14, when the initial case was detected in Japan, to the end of November, 2020, as of December 28. Because R(t) usually develops over time during the last one month. We inferred significance at the 5% level. During January 14 -November 30 in Japan, 137,726 community-acquired COVID-19 cases were identified as of December 25, excluding asymptomatic cases. The maximum delay was 30 days. Figure 3 depicts the empirical distribution of incubation periods among 91 cases for which the exposed date and onset date were published by MHLW in Japan. The mode was six days. The average was 6.6 days. Figure 4 depicts the estimated R(t), climate, and mobility in Japan. It is noteworthy All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted January 4, 2021. ; https://doi.org/10.1101/2020.12.29.20248977 doi: medRxiv preprint that R(t) is shown on the right axis; climate and mobility are on the left axis. The latter was normalized to have a zero average and one standard deviation. Table 1 presents the estimation results. Temperatures were negative and significant; mobility was positive and significant. Humidity was not significant. The emergency state and GTC were negative and significant, but SCVEC was not. Estimation results indicate that R(t) will increase by 0.52 if the temperature declines by 20°C. To cancel this effect, leaving on trips from the residence should be reduced by 50%. Therefore, temperature probably affects the outbreak dynamics. The emergency state reduced R(t) by about 1. However, GTC also reduced R(t) by about the same magnitude. GTC was presumed to have raised infectiousness to date, but it presumably reduced the infectiousness. At least, one can conclude that it did not raise infectiousness. This counterintuitive result might reflect the situation for July. Before GTC was started at the end of July, even though the temperature was high, a second peak occurred, indicating that the non-GTC period was affected by high infectiousness. By contrast, in November, R(t) was not so high compared to the first and second wave. Of course, the All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted January 4, 2021. ; https://doi.org/10.1101/2020.12.29.20248977 doi: medRxiv preprint temperature was lower than that it had been for the prior two peaks. The present study has some limitations. First, R(t) represents infectiousness, but not in the number of patients or cases of mortality. Actually, the third wave probably did not reach its peak by December 25, but the number of patients was already higher than in the prior two waves. One must be reminded that temperature and mobility are associated with infectiousness, but the result does not reflect association with the number of patients. To approach the association, a formal mathematical model incorporating temperature and mobility is needed. Producing that model is anticipated as a challenge for future research. Secondly, we examined this problem only for the entirety of Japan. Because Apple Inc. and the Japan Meteorological Agency provide information by prefecture, the data can be extended to affected prefectures such as Tokyo, Osaka, and Hokkaido. Thirdly, we do not know whether our result can be extended other countries. That effort remains as a future research objective. We demonstrated that mobility and temperature are associated with R(t). Moreover, we found that GTC did not raise infectiousness. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted January 4, 2021. ; https://doi.org/10.1101/2020.12.29.20248977 doi: medRxiv preprint The present study is based on the authors' opinions: it does not reflect any stance or policy of their professionally affiliated bodies. We acknowledge the great efforts of all staff at public health centers, medical institutions, and other facilities who are fighting the spread and destruction associated with COVID-19. All information used for this study was collected under the Law of Infection Control, Japan and published data was used. There is therefore no ethical issue related to this study. No author has any conflict of interest, financial or otherwise, to declare in relation to this study. Reference 1. Japan Times. Japan to suspend Go To Travel program nationwide from Dec. 28 to All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted January 4, 2021. ; https://doi.org/10.1101/2020.12.29.20248977 doi: medRxiv preprint Climate/mobility R(t) Note: Black line represents R(t). Orange and green lines respectively show humidity and temperature. Dots denote mobility. R(t) was measured by the right axis; climate and mobility were measured by the left axis. The latter was normalized to be zero average and one standard deviation. Impact of temperature on the dynamics of the COVID-19 outbreak in China Is temperature reducing the transmission of COVID-19 ? No association of COVID-19 transmission with temperature or UV radiation in Chinese cities Mobility data can reveal the entire COVID1-19 outbreak course in Japan Mobility Reduction and Covid-19 Transmission Rates Tokyo governor urges people to stay indoors over weekend as virus cases spike All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted Estimated effectiveness of school closure and voluntary event cancellation as COVID-19 countermeasures in Japan Effects of voluntary event cancellation and school closure as countermeasures against COVID-19 outbreak in Asymptomatic and Presymptomatic SARS-CoV-2 Infections in Residents of a Long-Term Care Skilled Nursing Facility All rights reserved. No reuse allowed without permission.(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint this version posted January 4, 2021. ; https://doi.org/10.1101/2020.12.29.20248977 doi: medRxiv preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint this version posted January 4, 2021. ; https://doi.org/10.1101/2020.12.29.20248977 doi: medRxiv preprint Figure 2 : Empirical distribution of duration from onset to report by MLHW, Japan. Note: Bars represent the probability of duration from onset to report based on 657 patients for whom the onset date was available in Japan. Data were obtained from MLHW, Japan.All rights reserved. No reuse allowed without permission.(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint this version posted January 4, 2021. ; https://doi.org/10.1101/2020.12.29.20248977 doi: medRxiv preprint All rights reserved. No reuse allowed without permission.(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint this version posted January 4, 2021. ; https://doi.org/10.1101/2020.12.29.20248977 doi: medRxiv preprint All rights reserved. No reuse allowed without permission.(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint this version posted January 4, 2021. ; https://doi.org/10.1101/2020.12.29.20248977 doi: medRxiv preprint All rights reserved. No reuse allowed without permission.(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint this version posted January 4, 2021. ; https://doi.org/10.1101/2020.12.29.20248977 doi: medRxiv preprint