November 5, 2018, 11:51 am | Read time: 6 minutes
This year, West Nile fever has reached Germany, sparking widespread fears. The virus responsible is insidiously transmitted to humans by mosquitoes. But how dangerous is it? And can it be prevented? FITBOOK consulted an expert on the matter.
According to the Robert Koch Institute, the West Nile virus (WNV) was first detected in birds and two horses in Germany in 2018. The Bavarian State Office for Health and Food Safety reported in October 2018 about a veterinarian who contracted the virus and fell ill. He likely became infected during the autopsy of a bird in the Ebersberg district through contact with its bodily fluids.
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This raises the question of how high the risk is for German citizens to also contract WNV. We answer this and other questions about the virus.
Where Does West Nile Fever Come From?
The virus was discovered in 1937 in a woman in the West Nile province of Uganda, who was suffering from an unexplained fever—hence the disease’s name.
The disease became globally known due to an epidemic in 1999 in the United States, likely triggered by a mosquito. This mosquito probably arrived on a flight from Tel Aviv to New York. By 2016, more than 46,000 people in the U.S. were reported to have contracted the fever, with 2,000 fatalities.
It is particularly widespread in Africa, especially in Uganda and Mozambique. Other risk areas include Egypt, India, Southeast Asia, and the Middle East. In recent years, cases have significantly increased in Southern Europe (Italy, Greece, France), Central Europe (Czech Republic, Hungary, Serbia, Austria), and the Black Sea states (Bulgaria, Romania, Moldova, Ukraine, Southern Russia).
How Is the Virus Transmitted?
The virus is primarily transmitted by mosquitoes and has been detected in 43 different species. Wild birds serve as the main hosts, allowing the virus to be transmitted from birds to humans via mosquitoes. Mammals like horses can also contract the virus, but they are not a source of the virus themselves.
There is also a risk of infection through organ transplants, blood transfusions, during pregnancy, and while breastfeeding infants. For example, blood donors who have been in a risk area are “deferred” for four weeks after their return.
How Does the Disease Progress?
The incubation period after infection is about two to 14 days. “Around 80 percent of those infected show no major symptoms. The remaining 20 percent develop a flu-like illness with fever, chills, and body aches,” says Dr. Maximilian Gertler, a specialist in internal medicine and tropical medicine at the Berlin Charité’s Institute of Tropical Medicine. Additionally, about half of those affected develop a rash over their entire body. The symptoms subside after about three to six days.
According to the Robert Koch Institute, about one in 150 infected individuals develops a severe form of the disease. “This is especially the case for older people and those with weakened immune systems,” explains Dr. Gertler. This can also include cancer and HIV patients.
In these cases, a usually benign meningitis can occur, which heals without lasting damage. In rare cases, it leads to encephalitis, which often results in long-term effects or death. “Unfortunately, encephalitis is difficult to treat in this case; only symptoms like fever and pain can be alleviated,” says Dr. Gertler from the Institute of Tropical Medicine in Berlin.
How Is the West Nile Virus Diagnosed?
Most people are unaware of their infection, and even with a flu-like course, the virus is not suspected. “That’s the insidious part; it’s not easily diagnosed. Most doctors don’t suspect it behind a flu-like illness. Additionally, diagnostic procedures are not widespread, and a specific blood test for the virus is expensive,” explains Dr. Gertler.
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Thus, even though there are no confirmed cases in Germany apart from the veterinarian from Bavaria infected in October, there may be an unknown number of people infected with WNV.
How Can I Protect Myself?
There is still no vaccine or medication against the West Nile virus. This means one can generally only protect against mosquito bites—with sprays, clothing, and mosquito nets. This is especially advisable in the particularly endangered regions we listed above.
Additionally, the Bavarian State Office for Health and Food Safety recommends not touching dead birds and contacting the veterinary office in case of clusters of dead birds.
Is Germany at Risk of an Epidemic Like the U.S. in 1999?
“It is not unlikely that the virus will spread more widely in Germany in the future. In the German winter, the risk of transmission by mosquitoes is very low, but it increases again with the warm season,” says the expert from the Charité’s Institute of Tropical Medicine. Whether the frequency will also increase due to longer and warmer summers cannot be determined with certainty at this time.
Also interesting: Why you always get sick—and others don’t!
There is no all-clear for West Nile fever in Germany, but the likelihood of becoming seriously ill from it is currently very low.
More Safety in Blood Donations Demanded
In light of the spread of the West Nile virus in Germany, tropical medicine specialist Jonas Schmidt-Chanasit calls for a new discussion on the safety of blood supplies. “Blood donation services need to address this more in the future,” said the expert from the Bernhard Nocht Institute for Tropical Medicine in Hamburg (BNITM). Only some services routinely test blood supplies for the viruses. Others defer donors who have been in certain countries for four weeks. “We should consider whether this is still sensible.”
So far, only some services routinely test blood supplies for West Nile and the closely related Usutu virus, said Schmidt-Chanasit. Currently, services that do not test must defer blood donors who have been in North America and some European countries where the West Nile virus is prevalent. “We should consider whether this is still sensible.” There is currently no regulation for the closely related Usutu virus.
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The Spread of West Nile Fever in 2018
In 2018, West Nile fever made or killed particularly many people in Europe. According to the EU health authority ECDC, there were over 1,460 reported infections in EU member states by the end of October.
At least 170 people died from the virus across Europe, most in the southern part of the continent. In comparison, there were only about 200 reported infections in the EU in the entire previous year. The agency counted 25 deaths in all European countries at that time. No other year stands out as much as 2018. In all years, the number of unreported cases is likely higher, as the virus often causes no or only mild symptoms.
In 2018, there were particularly many deaths in Europe in Italy (44), Greece (42), Romania (42), and Serbia (35). Deaths from infections are rare. About 80 percent of those infected have no symptoms, about 20 percent develop a feverish, flu-like illness. Only about one in 150 people—usually older patients with pre-existing conditions—becomes seriously ill with high fever and meningitis. Cold weather now contributes to the decline of the pathogens, which are mainly transmitted by mosquitoes, towards the end of the year.