All you need to know about coronavirus

Keeping COVID-19 at bay in Poland

The recommendation to stay at home, introduced in Poland six weeks ago, resulted in a considerable curbing of the COVID-19 epidemic. The reproduction number R (which measures the average number of persons that are infected by an infected individual) has decreased in Poland and is currently at the level of 1.02-1.04. Obviously, it would be highly desirable if this index were lower than 1.0, which would mean that the epidemic is in retreat. At this moment, however, the epidemic in Poland remains at a comparable, though rather low-intensity level.

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The economic costs of having the majority of citizens stay at home have been high. Therefore, the government decided to gradually lift restrictions. That means we are returning to functioning more or less normally while under epidemic threat, and if we do not follow security measures (maintaining at least 2 m distance in contacts with other persons, wearing masks in public places, washing hands frequently and measuring body temperature) the reproduction number may increase again. If it reaches 1.2 – 1.3, the epidemiological situation will become very serious again and the number of infected persons will grow sharply. In this scenario we would again be faced with the difficult decision of whether or not to send most people back home, to re-close schools, universities, restaurants, hairdressing salons, etc.

The COVID-19 epidemic is highly diverse spatially. It is more frequent in larger cities than in villages or small towns, where the intensity of human contacts, communication, transportation and trade networks is much lower. Apart from the spatial diversity, COVID-19 has one more specific feature that is relevant in the phase we are dealing with at a moment: namely, the R transmission number seems to vary from person to person. There are individuals who have an unusual “ability” to infect other people – these have been called “super-spreaders”. It is estimated that 80% of cases of COVID-19 are caused by just 10% of infected persons. In the case of super-spreaders the R number may as high as 8.0, whereas for many other infected individuals the figure may actually be 0. It is not yet clear why a given person with COVID-19 becomes a super-spreader. Super-spreaders can cause the epidemic to suddenly break out in places where they have spent significant time with other people.

Apart from the R transmission number, the epidemic is also described by the dispersion index k, which reflects the probability of the emergence of focal points of the epidemic. Such focal points have been observed all over the world, in Poland most recently in the coal mines of Silesia and a furniture factory in the Greater Poland Voivodship. Polish focal points have not yet been thoroughly investigated. Based on earlier outbreaks in such focal points in other countries, it has been observed that they usually take place in closed places where people are gathered next to each other. The chance of the emergence of epidemic focal point as a result of open-air events is considered to be rather low. Japanese researchers point out that the probability of contacting infection is 19 times higher in closed places than in open-air events. Outbreaks of COVID-19 have been observed onboard cruise ships, in old-age care centers, meat processing plants, churches, restaurants, hospital and prisons.  

An epidemic is usually over when a pathogen causing the disease disappears from the social space. In Poland, this is not yet the case. We are still exposed to the threat of the COVID-19 disease and most likely this situation will not change in the coming months. Therefore, in the near future we should in Poland:

  • maintain a distance of at least 2 m in contacts with other persons, wear face masks in public places, wash our hands very often and measure our body temperature,
  • increase the number of tests for COVID-19,
  • monitor the situations when there are many people in closed places,
  • if possible, organize public activities in the open air.