(CNN) — With cases reported in locations around the world, the spread of novel coronavirus has travelers on edge. Much is still unknown about the outbreak, and health officials are urging caution.

The US State Department on Sunday issued an advisory warning travelers against cruise travel.

“US citizens, particularly travelers with underlying health conditions, should not travel by cruise ship,” the warning reads.

“CDC notes that older adults and travelers with underlying health issues should avoid situations that put them at increased risk for more severe disease. This entails avoiding crowded places, avoiding non-essential travel such as long plane trips, and especially avoiding embarking on cruise ships.”

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All travelers should be aware of the virus, pay close attention to travel advisories, steer clear of heavily impacted areas and exercise preventive measures.

Here’s what travelers should know about the virus outbreak:

Cruise line cases and precautions

The State Department’s cruise advisory comes as the Grand Princess cruise ship, where more than 20 coronavirus cases were confirmed Friday, prepares to dock Monday at the Port of Oakland in California.

A multi-day disembarkation process and quarantining of passengers will follow, officials say.

In February, the Diamond Princess cruise ship was quarantined for two weeks in Yokohama, Japan. More than 700 people contracted the virus aboard the ship, and at least seven of those patients have died.

Cruise lines have recently instituted flexible rebooking policies.

Princess Cruise Line has created a temporary cancellation policy valid for cruises departing up to May 31, 2020.

Carnival Cruise Line recently sent letters to guests booked through May 31 offering options to reschedule and onboard credits for those who proceed with their plans. Other cruise lines have extended similar offers.

Many cruises to and from mainland China and other Asian destinations were canceled or modified earlier in the outbreak, according to Cruise Critic, an online cruise community and review site.

Cruise Lines International Association (CLIA) has continuously updated its protocols for members in efforts to prevent the introduction of the illness aboard ships.

CLIA members are to “deny boarding to all persons who have traveled from, visited or transited via airports in South Korea, Iran, China, including Hong Kong and Macau, and any municipality in Italy subject to lockdown (quarantine) measures by the Italian Government … within 14 days prior to embarkation,” one of the organization’s guidelines reads.

Denied boarding for anyone who has had close contact with anyone suspected to have coronavirus and pre-boarding illness screening and temperature checks are also outlined.

Individual cruise lines also have their own policies and screening procedures to guard against introducing the illness.

Flight cancellations and increased flexibility

Airlines all over the world have canceled flights amid the outbreak, and service to China has been suspended by many carriers.

Some airlines, including United, American, JetBlue and Delta, have recently built more flexibility into new bookings, waiving change fees for some travel periods in March.

United Airlines was the first US carrier to cut its domestic flight schedule due to a sharp drop in demand. United plans to cut flights in the US and Canada by 10% and overseas flights by 20% in April. Other carriers across the globe are similarly cutting services.

Delta has suspended flights between the United States and China through April 30. Service to Japan, Milan, Italy, and Seoul, South Korea, has also been impacted, and waivers have been issued for various destinations heavily impacted by the outbreak.

Other airlines, including British Airways, Lufthansa, Air France, Cathay Pacific, Qantas, Emirates and more, have similarly slashed or suspended service.

In Japan, Japan Airlines and All Nippon Airways have announced they will reduce the number of domestic flights as the country records a growing number of virus cases.

Travelers with upcoming plans should check with their airlines and look for advisories posted on carriers’ websites.

Airline cleaning efforts

Some airlines have bumped up their sanitation efforts to stem the virus’ spread, and the US Centers for Disease Control and Prevention recently released guidance on aircraft cleaning.

Delta Air Lines started using a fogging technique in February “with a highly effective, EPA-registered disinfectant” on flights arriving in the US from Asia.

Fogging is being performed on all trans-Pacific flights arriving into the US, the airline said, and those procedures are being expanded to more inbound international flights with a focus on flights coming from places with reported coronavirus cases.

While disinfecting is helpful, frequent hand washing is among a traveler’s best defenses, infectious disease experts say.

“Even if there is virus in the inanimate environment, it’s not going to jump off the seat and bite you in the ankle,” says Dr. William Schaffner, a professor of medicine in Vanderbilt University’s division of infectious diseases.

“You’ve got to touch it, and then touch your nose or your mouth. So it’s those hands we have that are the important intermediary. And that’s where I would put the emphasis,” he said.

The CDC advises washing hands often with soap and water for at least 20 seconds. An alcohol-based hand sanitizer with at least 60% alcohol can be used when soap and water are not available.

Traveler screening procedures

In a tweet on March 1, US President Donald Trump announced additional screening of travelers from “designated high-risk countries.”

Vice President Mike Pence said that anyone traveling to the United States on a flight from Italy and South Korea will receive multiple screenings before arriving in the United States. His comments were made during a coronavirus briefing at the White House on March 2.

Health screenings are already in place in the US for those traveling from China. American citizens, lawful permanent residents and their family members who have been in China within the last 14 days require screening at one of 11 designated US airports.

Those screenings involve a temperature check and observations for symptoms.

Foreign nationals who have visited China in the past 14 days are barred from entering the US.

US citizens and permanent residents returning to the United States who have traveled to Iran within the previous 14 days must enter through an approved airport. Foreign nationals who have traveled to Iran within the last 14 days will be denied permission to travel to the US.

Hand washing is a strong defense; masks are not

Dr. Schaffner has received a lot of questions about whether people should be wearing masks to avoid infection.

He realizes it’s culturally very common in Asia, but he says the CDC doesn’t recommend it for the general public because “the scientific basis showing that people in the community wearing masks actually has any benefit is very thin and questionable.”

More fitted respirator masks may be used in medical settings, but are generally impractical for the general public, Schaffner says.

Good hand hygiene is a better defense.

US Surgeon General Dr. Jerome Adams has urged the public to stop buying masks.

“There are things people can do to stay safe,” Adams said. “There are things they shouldn’t be doing and one of the things they shouldn’t be doing in the general public is going out and buying masks.”

He warned that the risk of infection can actually increase when masks aren’t worn properly.

Travel advisories

An increasing number of travel advisories have been issued by countries around the world, urging caution for select destinations, and discouraging travel to others.

The US State Department’s travel warning for China is at the highest level — Level 4: Do not travel. The department’s warning for travel to Iran, which was already at Level 4 prior to the outbreak, was recently updated to add information about coronavirus.

Travelers should reconsider travel to Italy and South Korea, according to the State Department, while travel to specific areas of those countries — Lombardy and Veneto in Italy and Daegu in South Korea — is discouraged. The department also advises travelers to reconsider travel to Mongolia.

Level 2 warnings, urging increased caution, are in effect for JapanHong Kong and Macau due to the outbreak.

The United Kingdom and Canada are among many other nations that have issued travel warnings for China, South Korea and other destinations.

The US Centers for Disease Control and Prevention (CDC) is discouraging nonessential travel to China, South Korea, Italy and Iran.

Japan and Hong Kong carry lower-level CDC advisories.

All travelers should avoid contact with sick people and clean their hands frequently.

Attractions closed and events canceled

Some museums in Milan, Paris, Japan and elsewhere have closed temporarily to stem the spread of the virus.

Disney parks in Asia are closed, as is Universal Studios Japan, and some of Japan’s crowd-pleasing cherry blossom festivals have been called off.

In Shanghai, Disneyland has reopened shops and restaurants but the theme park remains shut.

Travelers should monitor attraction closures and event status in their destinations.

Most travel insurance is unlikely to cover this situation

Airlines are relaxing their policies and some major hotel chains are waiving cancellation fees, but recouping all the costs associated with trips canceled due to coronavirus fears is far from guaranteed.

An outbreak of a virus is not covered under most standard trip cancellation insurance policies, according to TravelInsurance.com.

“For those who purchased a Cancel for Any Reason (CFAR) optional upgrade, however, some measure of trip cancellation protection may be available,” according to Stan Sandberg, co-founder of TravelInsurance.com.

Those holding existing policies should contact their providers to see if their plans offer any coverage.

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