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Title: Estimation of COVID-2019 burden and potential for international dissemination of infection from Iran
Abstract
CC-BY-NC-ND 4.0 International license It is made available under a author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
is the (which was not peer-reviewed) The copyright holder for this preprint . https://doi.org/10.1101/2020.02.24.20027375 doi: medRxiv preprint 2
The Coronavirus Disease 2019 (COVID-19) epidemic began in Wuhan, China in late 2019 and continues to spread globally (1) , with exported cases confirmed in 28 countries at the time of writing (2) . During the interval between February 19 and 23, 2020, Iran reported its first 43 cases with eight deaths. Three exported cases originating in Iran were identified, suggesting a underlying burden of disease in that country than is indicated by reported cases. A large epidemic in Iran could further fuel global dissemination of COVID-19.
To quantify the COVID-19 outbreak size in Iran based on known exported case counts and air travel links between Iran and other countries, and to anticipate where infections originating in Iran may spread to next.
We assessed interconnectivity between Iran and other countries using direct and total traveller volumes and final destination cities of travellers originating in Iran in February 2019, using data from the International Air Transport Association (IATA) (accounting for 90% of global air travel, with the other 10% modeled using market intelligence). As exported cases were identified in the United Arab Emirates (UAE), Lebanon, and Canada, we used the methods of Fraser et al (3) to estimate the size of the underlying epidemic in Iran necessary in order for these cases to be observed with a reasonable probability. To estimate the time at risk of COVID-19 exposure for travelers departing Iran, we obtained data from the United Nations World Tourism Organization (UNWTO) for the proportion of international travelers that are residents of Iran (4) . CC-BY-NC-ND 4.0 International license It is made available under a author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
is the (which was not peer-reviewed) The copyright holder for this preprint . https://doi.org/10.1101/2020.02.24.20027375 doi: medRxiv preprint and the average length of stay of tourists to Iran (5) , and assumed that the Iranian outbreak began in early January 2020. We evaluated the relationship between the strength of travel links with Iran, and destination countries' ranking on the Infectious Disease Vulnerability Index (IDVI), a validated metric that estimates the capacity of a country to respond to an infectious disease outbreak . Scores range between 0-1, with higher scores reflecting greater capacity to manage infectious outbreaks.
We evaluated travellers from Iranian airports (Tehran, Rasht, and Arak) to international destinations in February 2019. While Qom has reported cases, the international airport is currently being built. Global cities receiving the greatest number of total travellers from Iran Given the low rankings for Lebanon and Canada for outbound air travel, it is unexpected that cases should be identified in these countries, but not Iraq, Syria, or Azerbaijan (countries with higher travel volumes but low IDVI scores). Considering traveller volume alone, the odds . CC-BY-NC-ND 4.0 International license It is made available under a author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
is the (which was not peer-reviewed) The copyright holder for this preprint . https://doi.org/10.1101/2020.02.24.20027375 doi: medRxiv preprint 4 of a single case being imported into Iraq rather than Canada or Lebanon would be 33.6:1 and 15.4:1 respectively; for Azerbaijan, the odds would be 3.8:1 and 1.7:1, respectively; while for Syria, the odds would be 3.7:1 and 1.7:1 respectively. As such, we performed exploratory analyses in which we assumed that an unidentified exported case of COVID-19 was present in Iraq, Syria, Azerbaijan, or all 3 countries, in addition to Lebanon, Canada and UAE and estimated the outbreak size in Iran that would produce these results (Figure 2) . We also evaluated a scenario where we assumed perfect case detection in travelers from Iran, such that disease is truly absent in countries not reporting cases. Under this 'best-case' scenario, the estimated outbreak size in Iran was smaller but still substantial (1820, 95% CI: 380-5320 cases).
Given the low volumes of air travel to countries with identified cases of COVID-19 with origin in Iran (such as Canada), it is likely that Iran is currently experiencing a COVID-19 epidemic of significant size for such exportations to be occurring. Our analysis would be modified by travel restrictions from Iran due to recent political situations, and by variations in the R 0 value. Further, the lack of identified COVID-19 cases in countries with far closer travel ties to Iran suggests that cases in these countries are likely being missed, rather than being truly absent. This is concerning, both for public health in Iran itself, and because of the high likelihood for outward dissemination of the epidemic to neighbouring countries with lower capacity to respond to infectious diseases epidemics. Supporting capacity for public health initiatives in the region is urgently needed.
. CC-BY-NC-ND 4.0 International license It is made available under a author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
is the (which was not peer-reviewed) The copyright holder for this preprint . https://doi.org/10.1101/2020.02.24.20027375 doi: medRxiv preprint Figure 1 . Top 20 international cities connected to Iran by commercial air travel and associated vulnerability to infectious disease outbreaks. Vulnerability is measured by the country-level using the Infectious Disease Vulnerability Index score, with a lower value indicating reduced capacity to respond to outbreaks. Countries with the lowest IDVI score are indicated in red. The top 20 cities accounted for 70% of international outbound traveller volumes from Iran in February 2019.
. CC-BY-NC-ND 4.0 International license It is made available under a author/funder, who has granted medRxiv a license to display the preprint in perpetuity. author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
is the (which was not peer-reviewed) The copyright holder for this preprint . https://doi.org/10.1101/2020.02.24.20027375 doi: medRxiv preprint
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