It’s a worst-case scenario for many times over, and it’s happening in two European countries just 20 miles apart.

At least 120 people are known to have contracted the Crimean coronavirus (CCV) in the last three months in Crimea, a peninsula on the Mediterranean coast annexed by Russia in 2014, but doctors are still searching for up to 600 cases in the region.

“We have a powerful epidemiological infrastructure, but we are scrambling to know where people have been exposed,” said Aleksandra Naliskova, a medical doctor and researcher at the Joint Institute for Virology in Novosibirsk, Russia.

The virus is no stronger than cold viruses, but there are several that transmit rapidly between people, including SARS and Ebola. In March, the World Health Organization sounded the alarm and Russia shut off its borders for 30 days.

In Greece, where six people have been reported to have been infected with the virus, health officials and the European Commission tried to head off the crisis by banning all visits and cargoes from the region, canceling exams, public gatherings and meeting with patients. The European Commission also launched a monitoring network to monitor outbreaks.

In Washington, health officials have had to adapt. The virus spread quickly on board a passenger jet flying from Dubai to Athens. Between November 2013 and March this year, there were no cases until one was detected a month ago.

“In this case, an international traveler carried the virus from the region to Athens,” said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases. “That’s not much better than a civilian coming from Afghanistan or Iraq and bringing it here.”

Maryland officials closed an insecticide plant after finding traces of the virus in tree leaves. More about the CDC's outbreak response and response plans at arkiv.msd.gov/aboutus/sanity/.

Influenza has a history of clustering, and the virus didn’t stay at 1.5 percent that month. That suggests there could be a lot more cases.

“My first conclusion is that we have a virulent and lethal pathogen,” said John Howard, president of The Ohio State University College of Veterinary Medicine.

More worrisome, however, is the potential financial impact.

In the aftermath of the 2009 pandemic, many children in the U.S. got vaccinated. That’s because the CDC advised that children younger than 6 months should be vaccinated along with the general public to protect them from sudden pneumonia, which often comes from pertussis, or whooping cough.

The European Union instituted a similar rule for at least two years because adults can infect children with the virus and help spread it, while pregnant women aren’t affected by the disease.

“For almost a decade, we have taken appropriate measures to guard against further spread of influenza in Europe,” said Pierre De Clercy de Boursac, WHO’s representative in Belgium. “Fortunately, so far, there has been no evidence of continued transmission.”

Concentrations of the virus have been reported on the island of Karpathos and in western Greece.

“The situation in Greece appears to be rapidly improving but it remains a major concern,” De Clercy de Boursac said.

More cases are expected because the virus can linger for months and even years in some insects, which some have reported in their traps.

“Our theory is that the virus may survive in bat saliva and cross into humans. This is hard to determine because the virus appears to have switched species,” said Naliskova.

Because Ukraine borders Crimea, the virus seems unlikely to spread into Russia. The European Commission said it won’t be tightening any borders with countries in that region.

At the state and federal level, the CDC has been updating its pandemic pandemic response plan and asking states for advice.

“The last time we did a pandemic pandemic-control plan, the flu pandemic was a decade ago,” said Dr. Bruce Gilden, the director of CDC’s Office of Public Health Preparedness and Response. “We’re trying to understand the time, resources and implications of a new viral agent that is emerging.”