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Dr. Jean-Baptist du Prel
Photo: UniService Transfer

A pandemic can never be completely ruled out

An interview with the epidemiologist Dr. Jean-Baptist du Prel about the end of the Spanish flu 100 years ago

According to unconfirmed estimates, around 100 million people fell victim to the largest influenza pandemic of the 20th century. This mega epidemic went down in world history as the Spanish flu. According to current knowledge, however, it did not start in the sunny south of Europe, but at the army base Fort Riley in Kansas. The cook Albert Gitchell is often mentioned as one of the first patients. Within a few days more than 500 men fell ill in this military camp. How did the people get infected?

Jean-Baptist du Prel: The people at that time were infected in the same way as with the seasonal flu today. There are basically three transmission paths. One is the infection via droplet infection, even over several meters, and the other one is contact infection. For example, if I cough into my hand and shake hands with someone else, who than touches his mouth or nose as well. And the third possibility is indeed the smear infection, because the influenza virus has the property that it can survive outside the human body for a certain time depending on the temperature. Theoretically, it could be that someone reaches for an elevator button, the next person grabs the same spot and gets infected.

Why was the Spanish flu such a death-bringer?

du Prel: On the one side are pathogenicity properties in the pathogen itself, i.e. the basic ability of infectious organisms or toxins to make a particular organism sick. The Spanish flu was a variant of the H1N1 type, which was very morbific for humans. Such pathogens are caused by certain mechanisms. If a pathogen is completely new to the human organism, i.e. a subtype, it can infect humans particularly quickly. On the other side are characteristics in the host, which is, so to speak, surprised by a new pathogen, and the third aspect are the circumstances. It was war at the time and the pathogen first spread in a military camp. Such group facilities are the ideal conditions for spreading. Then it was brought to Europe  by the troops, including France and Spain. Increased mobility still plays a major role in the spread of the pathogen today. These troop movements meant that the pathogen could spread to other populations. And such masses of people as can be found in large cities today, also favour the spread of a pathogen due to the high contact rate.

Which treatment methods were available?

du Prel: Treatment methods were still limited 100 years ago. There were no vaccines against influenza back then, there was no antiviral (term here used for: medicine that inhibits the reproduction of the virus) and there were no antibiotics like we have today. What was done back then, was a purely symptomatic treatment. This still plays a role today. At that time, Aspirin was used, which also has an anti-inflammatory and pain-reducing effect and has a positive effect on the symptomatic course of the disease. Other methods were normal bed rest, inhalation or nasal showers on a symptomatic basis. People have also tried to adopt medication from other disease patterns. For example, quinine was administered, which successfully helped against malaria, but also morphine and heroin for the pain. And they also injected mercury at that time for reasons I cannot understand because they believed that it was helpful. So, partly martial aids.

According to a new study, the pathogen of the catastrophic Spanish flu is still in circulation today. Should we be worried?

du Prel: A subtype of the H1N1 virus also appeared in the 2009/2010 pandemic flu, i.e. the swine flu. This is actually the same strain. And through mutation or the transmission of entire gene segments, certain subtypes are always created which are either relatively new for humans or completely new. Today, the WHO (World Health Organization) expects that a certain part of the population is also infected with H1N1. However, it is by far not as pathogenic as the pathogen that caused the Spanish flu at that time. It is a different subtype. The H1N1 strain is of course still available in different variants. How great is the danger that we will get another pandemic like this? It can never be ruled out completely. It is a game of chance. And such pandemic strains as they appeared in the Spanish flu virus are always the result of the exchange of genetic information between different virus subtypes. So two influenza strains, a bird strain and a human pathogenic strain, exchange genetic sections. This in turn leads to the development of properties that are completely new to the human immune system, antigen structures that it does not yet know. This redistribution of genetic information between two similar viruses is called reassortment. This happens, for example, in pigs. Pigs have the property that they can be infected with both avian and human pathogenic strains. Then there is exactly this genetic information exchange and e.g. completely new H1, H2 or H3 units are created. The principle is actually always that the human immune system is surprised by something completely new. Such pandemic waves occur at certain intervals, but none were as bad as the Spanish flu.

Four million people died from the Asian flu in 1957, two million people died from the Hong Kong virus of 1968 and 311 people died from the current swine flu virus.
What protective measures do we have today, 100 years later, if a new pandemic were to occur?

du Prel: In most countries there are surveillance systems for influenza infections and they are running permanently, i.e. the WHO has an overview of where which pathogens are currently rampant. And in reconciliation with this, the WHO expresses recommendations for influenza vaccinations twice a year. Once for the southern and once for the northern hemisphere. And yet, one can never guarantee a 100% safety. The second aspect is that we have the possibility of vaccination, which did not exist in 1918/1919. We also have antivirals for severe cases, which alleviate the course of the disease. And there were no antibiotics for super bacterial infections back then. That was one of the main reasons why often they ended up fatally.

Flu vaccinations have been advertised more and more frequently in recent years. In the media there are both supporters and opponents. For whom do you think this vaccination is useful?

du Prel: I would like to follow the recommendations of the permanent vaccination commission at the Robert Koch Institute. These are mainly people over 60 years of age, because the immune system of these people is usually not so fit anymore. Pregnant women should be vaccinated in the 2nd trimester of pregnancy and if they have a basic suffering also already in the 1st trimester. Then persons with basic diseases such as asthma, cardiovascular diseases or kidney diseases. Then it is also recommended to people who are in contact with people that have an immune deficiency. And of course also people who work in the health system because otherwise they might become carriers for the patients. People who have increased contact with the public in communal facilities, and all people involved in bird breeding, because there is always the risk of double infection.

I, myself am a great advocate of influenza vaccinations because I think vaccination always has two faces. One is the personal protection and the other is the protection of fellow human beings, so I would be rather generous with the indication.

Uwe Blass (Interview on 07.01.2019)

Jean-Baptist du Prel studied human medicine at the University of Würzburg, where he also received his doctorate in 2000, and public health at the University of Düsseldorf. He was a research associate in epidemiology at the German Diabetes Research Institute at the University of Düsseldorf and a research assistant with teaching activities in epidemiology and medical biometry at the Universities of Mainz and Ulm. Since 2015, he has been a member of the scientific management of the Chair of Human Engineering at the University of Wuppertal, where he teaches preventive medicine, among other things.