“We studied confirmed COVID-19 cases over time in different European countries and saw a recurring movement pattern, from southwest to northeast, during the infection waves of some COVID-19 variants. We are cautious about highlighting individual causes or underlying factors, but we can see a significant pattern,” says Karin Ebert, docent at Södertörn University and one of the researchers behind the study. External link.

Adding to knowledge about COVID-19

The state of knowledge about SARS-CoV-2, the virus behind COVID-19, has gradually improved since outbreak started in 2020. However, despite extensive research, there are still gaps to be filled – such as studies of regional spread patterns.

“I became very interested in data and statistics about covid during the pandemic. After a while, I thought I could see a pattern, so I started digging in the literature for an explanation. I found articles showing similar spread patterns, but for other respiratory viruses such as influenza and RSV. I began to suspect that what I was seeing might be correct and contacted two colleagues who study outbreak patterns,” says Karin Ebert

These colleagues are Patrik Dinnétz and Thérese Janzén, both researchers in environmental science. Together, they have mapped data on the number of confirmed cases per capita in 28 European countries, focusing on the peaks of infection waves for different COVID-19 variants.

“Not all the virus variants follow the same pattern, there are some that deviate, but the vast majority follow a southwest-northeast direction,” says Patrik Dinnétz, senior lecturer in environmental science.

Causes are still unknown

Researchers do not yet know why these distribution patterns occur. In the article, they discuss potential factors such as climatic conditions, infection control measures and recommendations from health authorities. One theory that Ebert would like to test is that of sea air’s influence.

“In another study, I analysed the relationship between sea air and the number of COVID-19 cases in five different European countries (Italy, Spain, Germany, Sweden and Norway). Statistically, we saw lower numbers of cases on the west coasts, where the most sea air flows in, such as in northwest Spain, the west coasts of Italy and Norway, and northwest Germany. I’ve now applied for funding to study whether and how sea air can affect respiratory tract infections,” says Ebert.

Increased knowledge helps healthcare services

Increased knowledge can provide more support for healthcare professionals in making decisions, planning and managing the spread of viral infections.

“It can help with anticipating which vaccines to prepare. This year’s flu vaccine works against three different virus strains. Decisions about which strains to focus on each year are made using knowledge about global (WHO) and regional distribution patterns. Knowledge about these patterns can also be useful at the individual level, as people could plan their travel based on them,” says Thérese Janzén, PhD in environmental science.

The virus does not spread on the wind – but the environment may matter

Making associations with sea air and winds does not mean that the virus travels with the wind. The researchers emphasise that both COVID-19 and influenza are droplet infections that spread from person to person – not through air currents over long distances.

“The droplets are very small and can stay suspended in the air for various lengths of time, but they only move over very short distances. The droplets can be transmitted directly, through inhalation, but also indirectly, because droplets that land on solid surfaces can be transferred to our hands and then to our eyes, nose and mouth – so a good way to stay healthy is make sure you wash your hands,” concludes Patrik Dinnétz.