DIt seems a long time ago, when time and money were the main constraints for planning a vacation trip. The possibility of unrestricted visits to foreign countries is currently a long way off. This is obvious at first glance, because in order to limit the spread of the pandemic, it is useful to limit the movement of potentially infected people as much as possible. After all, as long as the countries at the national level are trying to get the pandemic under control, it does not help if new cases of infection are imported from outside at the same time. Based on previous experience, it is not easy to answer whether this consideration is really correct, whether the travel restrictions are necessary or, on the contrary, may be dispensable in combination with other measures. The development of the number of cases ultimately owes to the combined effect of a large number of factors that are difficult to separate in their influence.
Anyone who tries to understand how individual measures have worked, and what that means for our future approach to the pandemic, must consult scientific models. In these models, which simulate the course of the global spread of an infectious disease, measures can be switched on and off as required, resulting scenarios can then be compared with one another and with available data.
For the question of the effectiveness of travel restrictions, a research group led by Neil Ferguson from Imperial College in London did so long before the new coronavirus Sars-CoV-2 appeared. In 2007, they simulated the spread of a pandemic in the United States and Great Britain, taking into account restrictions on travel options: on the one hand, in the form of border controls, which should be able to prevent more than 90 percent of those infected from entering the country, and on the other hand, as restrictions on freedom of movement within the countries. The result: the point in time when the measures begin is crucial. Efficient border controls can delay the progression of the disease by a few weeks at the beginning of the pandemic, if there are still a few cases in the country. Together with such an entry control, national travel restrictions can further slow down the spread of infections. According to the model, up to two months of time can be saved in this way.