Adrian Egli

Infection routes in Basel

This last winter brought an influenza wave to Europe, unrivaled by many others. Adrian Egli, Head of the Division of Clinical Microbiology at the University of Basel, investigated the spread in Basel and explains why this year's flu outbreak was one of the worst ever measured. Now he is planning a new project together with Richard Neher – this time not on influenza, but on multi-resistant hospital pathogens.

“If you think: ‘Hmm, maybe I have caught the flu,’ then you can be sure that it is not the case,” says Adrian Egli. “Having the flu makes you feel so ill with high fever within a few hours. You don't even wonder if it could be the flu; you know it immediately.” Together with scientists from the ETH Zürich and the Department of Environmental Sciences of the University of Basel, Egli has investigated the spread of the flu virus in Basel. They distributed about 30 000 questionnaires to hospital patients and patients of local doctors to find out where the infected people live, where they work or which tramlines they use in order to create a transfer model for the entire city.

This winter’s wave of flu was one of the worst flu outbreaks ever measured. Almost five times as many cases were counted as in the previous year. As it was extremely cold, even before Christmas, the spread of the flu began two months earlier than usual. “Temperature has a strong impact as the viruses survive mainly on cold surfaces – on automatic doors, at the ticket machine, at the traffic lights or on door handles,” explains Egli. Additional factors that influence the spread are the virus itself and how the immune system of the population responds to it. “Most probably this year’s virus was a new variant and therefore difficult for our defense system to recognize.” The most effective way to avoid an infection is to have the flu vaccination. But to entirely prevent the annual flu wave, a vaccination rate of 50 to 60 percent of the population would be necessary. “At the moment we are miles away from that,” Egli comments.

In Switzerland about 30 percent of the over 65 year olds are vaccinated, of people below the age of 65, less than 15 percent. There is no mandatory vaccination. Even doctors are not obliged to be vaccinated. “Nevertheless, I get vaccinated every year. Not just for my own health but also not to be a carrier who might infect other patients.” That’s why Adrian Egli recommends that all people who are in contact with chronically ill, immunocompromised or elderly people should be vaccinated annually.

About a quarter of a million people in Switzerland succumb to the flu each year. About 1 500 of them die. Apart from these sad individual outcomes, the economic impact is enormous. “If one imagines that about half of the 250 000 infected people are unable to work for one week, then the cost of absenteeism due to sickness over the year is expected to be in the billions,” emphasizes Egli. The resulting costs for medication, doctor’s visits or hospital stays are not even taken into account in this calculation. Hence, consistent vaccination against influenza would not only be a health measure but also a very cost-effective preventive measure. A simple way to prevent an infection is by regular handwashing and disinfection – and avoiding large crowds of people. "Maybe one should cancel the Basel Carnival. But of course no one would do that!” Egli says with a smile.

Currently he is planning a project together with Richard Neher – not on influenza, but on another, equally present-day microbe: a multi-resistant variant of the bacterium Staphylococcus aureus (MRSA), the so-called “hospital bacterium”. As there is a worldwide problem with the increase in multi-resistant organisms, they would like to use the tool “” to analyze the spread of multi-resistant bacteria in Swiss hospitals. “Within the framework of the National Research Program for the Study of Antibiotic Resistance, we will investigate the epidemiology of infections and resistance in order to better understand the dynamics of the bacteria transmitted in the hospital or from the environment,” he points out. 

Another example is the normal intestinal microbe E. coli. Nowadays, in Swiss hospitals, about 12 percent of the bacterial population is already multi-resistant to the common antibiotics. Each year this increases by one percent. E. coli is found in all bodies of water and colonizes 80 to 90 percent of the surface of fresh chicken meat. It is found on cutting boards in the kitchen, it is in our environment, in our food chain – simply everywhere. People are constantly in contact with multi-resistant pathogens. But this does not mean that they will get sick. “Our own bacteria provide a natural protective barrier. Even if we come into contact, we do not remain carriers,” so Egli. 

Antibiotic resistance itself is something natural. It doesn't exist just because antibiotics are used in the clinic. Antibiotic resistance has been around since bacteria first existed. Bacteria themselves produce antibiotics in the fight against competitors. So, the bacteria themselves are naturally resistant to their own antibiotics. “The problem is rather in how we deal with antibiotics and that there is no commercial interest to actively look for new ones as not much money can be made with antibiotics. One can only hope that a rethinking takes place and that pharmaceutical companies invest more in this area,” concludes Egli.