Vibriosis is caused by the bacteria Vibrio (vibrions), which thrive in warm and slightly saline coastal waters. The Baltic Sea, the North Sea and especially the Black Sea are particularly risky in Europe.
In the Baltic Sea, sea temperature is rising and salinity is decreasing - both trends that researchers link to climate change. As temperatures rise, cases of infections with the bacteria Vibrio are increasing.
These infections have so far been relatively rare in Europe, but health authorities, including the European Centre for Disease Prevention and Control (ECDC), are warning of an increased risk during the summer months with prolonged heat.
What is vibriosis?
Vibrio bacteria cause vibriosis and cholera. Vibriosis is an infection that can be life-threatening - especially in people with weakened immune systems.
The most important types of vibrio bacteria that cause infections in humans are Vibrio vulnificus, Vibrio parahaemolyticus and Vibrio alginolyticus. However, there are at least a dozen other types.
Some infections can lead to tissue necrosis (so-called necrotizing fasciitis). Rarer infections with Vibrio vulnificus, also called the "man-eating bacteria", can cause serious illnesses that require intensive medical care or even amputations.
In the United States, an average of one in five people infected with Vibrio vulnificus dies within two days of infection, according to the Centers for Disease Control and Prevention (CDC). There are about 80,000 illnesses and 100 deaths caused by the bacteria in question in the United States each year.
How does vibriosis infection occur?
Most people become infected through the digestive tract by consuming raw or undercooked seafood, such as oysters and clams.
Infection can also occur by swallowing water when swimming in infected coastal waters or after water enters open wounds.
Who is particularly at risk?
People with pre-existing conditions are at higher risk. This group includes people with liver damage due to hepatitis, liver disease, or excessive alcohol or drug use. People with cancer, diabetes, or HIV are also at risk. This also applies to people undergoing immunosuppressive therapy or taking medications to suppress stomach acid.
Vibriosis cannot be transmitted from person to person.
How to protect yourself?
It is recommended not to consume raw or undercooked shellfish. Health authorities also advise against swimming in salty seawater with open wounds. If you are injured while swimming, get out of the water, clean and disinfect the wound, and bandage it properly.
If you have a pre-existing medical condition, a weakened immune system, or have recently had surgery, consult your doctor before swimming in an affected coastal area.
What are the symptoms of vibriosis?
Symptoms depend on the type of infection, but are often similar to those of other infections, such as the flu or gastrointestinal illnesses: diarrhea, cramps, nausea, vomiting, chills.
Signs of sepsis caused by vibriosis include extremely low blood pressure and blistering around skin lesions.
Vibriosis wound infections can cause redness, pain, swelling, and drainage from wounds.
Where are the dangerous bacteria most common?
In Europe, the Baltic Sea is affected with its coastal regions in Denmark, northeastern Germany, Finland, Estonia, Latvia, Sweden, Lithuania, Poland and Russia.
In the North Sea, the bacteria thrive along the Dutch and Belgian coasts.
In southern Europe, the particularly risky region of the Black Sea is located - therefore there is a danger in Romania, Bulgaria, Turkey and Ukraine.
In Europe, several hundred cases of vibriosis are registered every year. In 2018, there was a significant increase in infections - 445 in total.
North America, Canada and Southeast Asia are also affected.
Coastal regions are ideal places for the vibrio bacteria to breed - firstly, because they are a mixture of salt and fresh water, and secondly, because they are often closed waters in which the bacteria can breed almost undisturbed.
Is climate change the cause of the increase in infections?
Earlier this month, the European Centre for Disease Prevention and Control warned that vibrio bacteria were finding increasingly favourable conditions in parts of Europe due to climate change. And before that, the European Environment Agency (EEA) linked recent marine heatwaves to "unprecedented cases of vibriosis along the Baltic and North Sea coasts".
Research over the past decade has shown that climate change is causing more river water to enter the Baltic Sea, which is reducing its salinity.
So while climate change is not the main cause of vibriosis, it is certainly increasing the threat.
Author: Zulfikar Abani