Abstract
The rapid expansion of coronavirus disease 2019 (COVID-19) has been observed in many parts of the world. Many newly reported cases of COVID-19 during early outbreak phases have been associated with travel history from an epidemic region (identified as imported cases). For those cases without travel history, the risk of wider spreads through community contact is even higher. However, most population models assume a homogeneous infected population without considering that the imported and secondary cases contracted by the imported cases can pose different risks to community spread.We have developed an “easy-to-use” mathematical framework extending from a meta-population model embedding city-to-city connections to stratify the dynamics of transmission waves caused by imported, secondary, and others from an outbreak source region when control measures are considered. Using the cumulative number of the secondary cases, we are able to determine the probability of community spread.Using the top 10 visiting cities from Wuhan in China as an example, we first demonstrated that the arrival time and the dynamics of the outbreaks at these cities can be successfully predicted under the reproduction number R0 = 2.92 and incubation period τ = 5.2 days. Next, we showed that although control measures can gain extra 32.5 and 44.0 days in arrival time through an intensive border control measure and a shorter time to quarantine under a low R0 (1.4), if the R0 is higher (2.92), only 10 extra days can be gained for each of the same measures. This suggests the importance of lowering the incidence at source regions together with infectious disease control measures in susceptible regions. The study allows us to assess the effects of border control and quarantine measures on the emergence and global spread of COVID-19 in a fully connected world using the dynamics of the secondary cases.
Highlights
On 31 December 2019, the World Health Organization (WHO) was alerted to several cases of pneumonia infections in Wuhan City, Hubei Province of China [1]
Because a person who was infected can travel to another region and spread the virus, COVID-19 continued to pose a severe threat to other regions through transportation services
Many newly reported cases of this new coronavirus infection in other cities or countries before community spread have been associated with travel history from an epidemic source region or contact history to people from the region, referred as the imported cases and the secondary cases transmitted from the imported cases respectively
Summary
On 31 December 2019, the World Health Organization (WHO) was alerted to several cases of pneumonia infections in Wuhan City, Hubei Province of China [1]. One of the most urgent public health tasks is to prevent the spread of the virus from an epidemic source region to other regions within a country or globally. Because a person who was infected can travel to another region and spread the virus, COVID-19 continued to pose a severe threat to other regions through transportation services. Many newly reported cases of this new coronavirus infection in other cities or countries before community spread have been associated with travel history from an epidemic source region or contact history to people from the region, referred as the imported cases and the secondary cases transmitted from the imported cases respectively. Once the secondary cases continue to transmit to more local cases, infection chain is established in the community, community spread begins subsequently [5]
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