Zagreb Sprays Against Mosquitoes for West Nile. Croatia Has a Normal Year, Netherlands Two Dead

Zagreb on Tuesday morning released vehicles with insecticide mist into the streets. Croatia has seven confirmed cases of West Nile virus, four patients lying in an infectious disease clinic and two of them in intensive care. Croatian experts nevertheless describe this as a typical seasonal picture — and the most serious reports this week are not coming from Croatia, but from the Netherlands. Since then the picture has changed in two places at once: the Dutch institute raised the number of domestic infections from four to nine and Greece reports 290 cases and 24 dead.

What exactly is Zagreb doing

Spraying took place from four to seven in the morning, that is, when there are the fewest people outside. Vehicles carry equipment that converts insecticide solution into mist with droplets smaller than 50 microns. These float in the air and then settle on vegetation and other surfaces. Index.hr ↗

Ana Klobučarová, head of the disinfection and deratization department of Zagreb's hygiene institute, emphasizes that more important than action against adult mosquitoes is tackling larvae in water. Larvicide measures therefore cover everything from sewers in urban and suburban neighborhoods through quieter sections of streams to buckets and barrels in gardens and street drains. Spraying continued in Bartol Kašić park, around Kvaternikov Square and in the neighborhoods of Savica, Bundek, Zapruđe, Utrina, Travno and Sloboština. HRT ↗

The city recommended residents not to stay outside during the operation and to close windows. Beekeepers received a special call — they should close their hives because bees are extremely sensitive to insecticides. It is a detail that shows the scope of the measure: this is not a spot disinfection, but a blanket intervention in the urban ecosystem.

The trigger was not just human infection. The virus was found in five dead crows at different locations in the city, and that is a signal for epidemiologists that the virus is circulating in the locality. Zagreb residents therefore also received instructions on what to do and who to call when they see a dead crow. N1 Croatia ↗

Why no one in Croatia is calling this an epidemic

We need to pause here because the report of spraying sounds more dramatic than the numbers behind it. Of the seven confirmed cases, two people are from Krapina-Zagorje County and hygienists in their surroundings have ordered anti-epidemic measures. At the same time, however, seven reported infections are, according to Croatian experts, a typical picture of occurrence in the country. Index.hr ↗

This is also helped by the profile of the disease itself. Seventy to eighty percent of infected people have no symptoms at all and most of the rest overcome something like the flu. Severe neurological complications — meningitis or encephalitis — affect fewer than one in a hundred infected people. This is precisely why the number of confirmed cases cannot be read as the number of infected, but rather as the number of those who ended up at a doctor.

Croatia is therefore doing what it has practiced. Neighboring Serbia is in a similar situation: from June 1 to August 30, they recorded 18 cases in seven districts, seven more than a week earlier. The average age of infected people is 63.2 years, which corresponds to the fact that severe illness threatens especially the elderly. The season there usually lasts from June to November and the main transmitter is the mosquito species Culex pipiens. Danas ↗

An unexpected number came from the north

If West Nile surprised anyone this year, it is not the Balkans. On the same day that Zagreb was spraying, Dutch authorities confirmed infection in a 39-year-old woman from Amstelveen near Amsterdam. The key point is that she contracted the virus in the Netherlands, not on holiday, and developed meningitis. NOS ↗

By Wednesday, this number more than doubled. The Dutch institute RIVM reports nine people who became infected directly in the Netherlands — just a week ago there were three. Cases come from the provinces of Utrecht, North Brabant, North Holland and South Holland. One of the infected, a man over 75 years old from Utrecht with underlying health problems, died and the institute lists him as the first death from infection acquired directly in the country. Along with him, a woman from the Drenthe region also succumbed to the virus in August, but RIVM does not include her in this count. The probability of infection continues to be rated as very low. NOS ↗ NU.nl ↗

However, Greece has the worst numbers in Europe and does not fit the pattern of "the south is used to it." The National Public Health Organization EODY, as of September 2, records 290 confirmed cases and 24 deaths, with 58 new infections in just the last week. Sixty-three patients are in hospitals, including 32 in intensive care units. The most affected is the Athens agglomeration — Pallini, Marathon, Acharnes and northern suburbs including Agia Paraskevi and Chalandri — and spraying is taking place directly around the capital. Balkanweb ↗ TVN24 ↗

The difference is therefore not between south and north, but between what these numbers mean in individual countries. Seven cases in Croatia is a repetition of a known pattern in a country that has a practiced apparatus for it. Nine domestic infections and the first domestic death in the Netherlands are a more significant signal precisely because the local institute still rates the risk of infection as very low. And 290 cases with 24 deaths in Greece show that "a normal season" in southern Europe can mean this too.

A different mosquito, a different disease, a similar concern

Health authorities are following the same pattern with another disease. It is not just about the number of cases, but about where the vector has already established itself. In the Italian town of Cuneo in Piedmont, Mayor Patrizia Manasserová issued an order for emergency measures on Monday after the local health authority announced a suspected case of chikungunya virus infection. La Stampa ↗

The wording in the order itself is interesting. Chikungunya is transmitted by mosquitoes of the Aedes genus, including the tiger mosquito, which according to the city is "permanently present" on its territory. Not introduced, not seasonal — established. This is a state that can create conditions for local transmission if the suspicion is confirmed. However, Cuneo so far only reports suspected infection.

What this means for vacationers

Croatia is the number one holiday destination for Slovaks and Czechs and spraying in Zagreb sounds like a reason for concern. But the numbers do not support this — the risk is comparable to other summers and city spraying is rather a sign of a functioning health service than a failure.

More practically useful is what the Croatian hygienists themselves recommend and what applies equally at home: repellents, long sleeves and trousers during times of greatest mosquito activity, window screens, and especially removal of standing water. Buckets, barrels, vases, flower pots and old tires should be emptied at least once or twice a week because it is in these that larvae hatch.

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