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The Growing Outbreak on Oʻahu

2:04 AM · Aug 5, 2020

Preliminary Analysis IV There is growing cause for concern in Hawaiʻi as Oʻahu’s COVID-19 case numbers surge. Oʻahu currently accounts for 67% of Hawaiʻi’s population whereas Oʻahu represents 85% of the COVID-19 cases in the state. The difference between Oʻahu and neighboring island is also shown in the recent positivity rates (I dubbed this a “hit-rate” before “positivity rate” became commonly used). As in previous analyses, this post will look at the positivity rates on COVID-19 testing results to compare the prevalence of infection in Hawaiʻi to the mainland. Also, it looks at the amount of passenger arrivals coming into Hawaiʻi compared with 2019, and reviews the mobility data available from Google and Apple. In the first COVID-19 analysis posted on Hawaiʻi Tracker in late March the positivity rate on antigen testing was identified as one of the key indicators to watch over time. The positivity rate on testing provides a means to compare Hawaiʻi to other regions battling the pandemic, a metric also used by the Hawaiʻi Department of Health. In late March, the positivity rate throughout the state was less than 2%, and was roughly consistent from then until July, whereas currently the running 7-day average has risen up to 6.4% on Oʻahu [1]. Positivity Rates on Testing Seven day averages by island, August 4th: Oʻahu - 6.4% (and rising) Hawaiʻi - .8% (and rising) Kauaʻi - 0% Maui - .9% PCR testing results provided by Hawaiʻi Department of Health show that testing capacity has roughly doubled between April and July. However, the rate of positive results returned has risen in the same time. Looking at the distribution of cases it’s clear that there are currently two different trajectories in Hawaiʻi: the growing outbreak on Oʻahu, and little change on the neighboring islands. The current 7-day average on the positivity rate across the nation is at 8%. The amount of tests processed has been picking up across the US, but that trend has been outpaced by positivity rates in July [2]. In late July the positivity rate on the US mainland stabilized around 8%, in contrast to Oʻahu which saw a dramatic rise in positivity during the same period. The World Health Organization has cited a positivity rate of 5% as being a threshold for greater concern in a particular region [3]. As a state Hawaiʻi is just below that threshold on a 7-day average, currently at 4.8%, but that positivity rate is trending up and will likely cross that 5% threshold based upon recent results [1]. Visitation and Mobility Data In March, Hawaiʻi saw nearly a 99% drop in passenger arrivals from domestic and international travelers. Since then, state-wide arrivals have only crept back, primarily on Oʻahu, with the highest days of travel since the pandemic began still less than 8% of the 2019 levels. Oʻahu has seen passenger arrivals around ten times greater than each neighboring island over the course of July, 2020 [4]. Passenger Arrivals in the State by Month April: ~400 passengers a day May: ~800 passengers a day June: ~1,400 passengers a day July: ~2,000 passengers a day August (so far): ~2,900 passengers a day The mobility data provided by Google and Apple highlight the percent change in visits to places like grocery stores and parks compared with a baseline for activity. Hawaiʻi’s mobility baseline is likely skewed by the departure of tourists in March. After the huge drop-off in visitation in March, mobility data showed significant decreases in restaurants, grocery, parks, bus stations, and workplaces. Since then the mobility of residents has rebounded slightly in May, June, and July [5]. Hawaiʻi Department of Transportation highway monitoring of roadway traffic show a similar large decrease in the state averaging between 30-50%. Hawaiʻi DoT’s data shows similar partial resumptions in traffic flow in the months following March, generally recovering roughly half of the initial reduction in traffic at designated sensors. Compared with other US states, Hawaiʻi has seen more reductions in retail, parks, and transit stations [6]. Conclusion Oʻahu presents a challenge going forward as there is likely a growing outbreak based on positivity rates as a leading indicator. The vast majority of cases in the recent weeks have been related to community spread on Oʻahu, suggesting the growing prevalence of the virus in the population, and less importance on travel related cases. The virus has gained a foothold in Honolulu that makes management more difficult across the state. Lt. Gov. Josh Green has recently mentioned the potential need for another statewide shutdown in his estimation if trends continue to deteriorate, however the most concerning trend at the time of writing applies mostly on Oʻahu [7]. References [1] - Hawaii Department of Health (2020), Current Situation in Hawaii [2] - Johns Hopkins (2020), Daily State-By-State Testing Trends, [3] - Johns Hopkins (2020), WHICH U.S. STATES MEET WHO RECOMMENDED TESTING CRITERIA? [4] - Department of Business, Economic Development & Tourism (2020), DOMESTIC PASSENGER COUNTS [5] - Google (2020), COVID-19 Community Mobility Report, [6] - Hawaii Department of Transportation (2020), COVID 19 TRAFFIC VOLUME COMPARISON, [7] - Allison Schaefers (2020), Star Advertiser: With coronavirus cases spiraling, Lt. Gov. Green says statewide lockdown might be only way out.

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