The number of coronavirus infections — and fatalities — has jumped in recent days. The pneumonia-causing illness that infects the respiratory tract is now responsible for 106 deaths in China as of Tuesday, up from 82 the day before, and more than 4,600 infections, up from 2,744 on Monday, the biggest rise in one day since the virus was first diagnosed in December, health officials in China said.

The outbreak has spread rapidly in over the last seven days. It is believed to have originated in Wuhan, likely at a food market. On Sunday, Zhou Xianwang, the Mayor of Wuhan, said that 5 million people had left the city before travel restrictions were imposed ahead of the Chinese New Year. China also said that it will refurbish and re-open the Xiaotangshan Hospital on the outskirts of Beijing, built during the 2002-2003 SARS outbreak.

The U.S. State Department ordered the evacuation of all U.S. personnel at the Consulate in Wuhan. It infected people in Hong Kong, Australia, Malaysia, Thailand, France, Japan, Taiwan, Vietnam, Singapore, South Korea, Macao and Nepal. There have also been five confirmed cases in the U.S., U.S health officials said.

In an effort to stem the spread of the virus from its suspected origin, transport bans were instituted in 16 cities with a combined population of 50 million people. Officials in Wuhan, a city with 11 million residents, said they had temporarily closed the area’s outgoing airport and railway stations, and suspend all public transport. Long-distance trains and buses from Huanggang, a neighboring city with 7.5 million people, will stop running indefinitely from midnight Friday local time.

The spread was helped by China’s Lunar New Year holiday, which began Friday. “This is the wild card,” Tanner Brown, a Beijing-based journalist, wrote for MarketWatch. “People unfamiliar with China have trouble understanding the immense travel phenomenon that occurs during Lunar New Year, when, over a one-month period, some 3 billion people are on the move, many returning to their home towns and regions but others vacationing. Peak travel occurs this week.”

The virus has spread in China, helped by the country’s Lunar New Year holiday.

Another reason for the rapid spread: While some people are canceling travel plans in China and opting to stay home over the holiday period, others may not yet have experienced the worst of the symptoms, believe themselves to be well enough to travel and/or could be reluctant to pay up to $400 to change a flight — especially if they believe they merely have a common cold. In fact, previous iterations of the coronavirus are very similar to a common cold.

People may not know they’re carrying the virus, and doctors don’t yet know how long it takes to develop. Symptoms include a runny nose, headache, cough, sore throat, fever and a general feeling of being unwell, according to the CDC.

Ma Xiaowei, the director of China’s National Health Commission, said that the virus had an incubation period of 10 to 14 days, during which the virus can be contagious but the patients does not display symptoms. That would mark a major difference between the coronavirus and SARS.

“From observations, the virus is capable of transmission even during incubation period,” Ma told a news conference, according to a report in the South China Morning Post. “Some patients have normal temperatures and there are many milder cases. There are hidden carriers.”

Previous iterations of the coronavirus are very similar to a common cold.

But more severe coronaviruses can become more serious and progress to pneumonia. “Human coronaviruses can sometimes cause lower-respiratory tract illnesses, such as pneumonia or bronchitis,” it added. “This is more common in people with cardiopulmonary disease, people with weakened immune systems, infants, and older adults. Two other human coronaviruses, MERS-CoV and SARS-CoV have been known to frequently cause severe symptoms.”

Nasty bugs like coronaviruses can last for days on objects. The sinister sounding Methicillin-resistant Staphylococcus aureus (more commonly known as MRSA) lasted longest (168 hours) on material from a seat-back pocket while the bacteria Escherichia coli O157:H7 (also known as E.coli, which can cause kidney problems) survived longest (96 hours) on the material from the armrest of planes, according to research presented in 2014 to the American Society for Microbiology.

In an attempt to remain competitive, airlines have decreased their turnaround times in recent years. Many budget airlines have reduced turnaround times to 25 minutes by removing the seat pockets. Other airlines have managed to have long-haul turnaround times of 90 minutes. Not only do planes get new plane load of passengers, they often get a completely different crew. Deep cleans are not always possible during such turnarounds, which could aid in the transmission of the coronavirus.

Office workers pick up 30% to 50% of the organisms that are left on surfaces.

After flying, most people take public transport. You may avoid stainless steel poles on subways and buses, but do you touch turnstiles and ticket machines? They are arguably touched by even more people, says Charles Gerba, a microbiologist at the University of Arizona. Commuters are 6 times more likely to develop an acute respiratory infection if they traveled recently by bus or tram, a 2011 published in the BMC Journal of Infectious Diseases concluded.

What can you do? Aisle seats will be touched most often by other people as they’re trying to find their own, Gerba says. In 2008, members of a tour group experienced diarrhea and vomiting in an airplane flight from Boston to Los Angeles. Other passengers who suffered secondary infections were either sitting next to those infected — or unsuspecting passengers seated in aisle seats, according to a study published in the journal Clinical Infectious Diseases.

We may move away if we see someone sneeze at the water cooler or on a train, but touching objects is a faster way to transmit viruses, Gerba says. He recommends using hand sanitizers or disinfectant wipes, particularly at the office where people may be reluctant to stay home if they’re sick. One 2014 study, presented at an American Society for Microbiology meeting in Washington, D.C., office workers pick up 30% to 50% of the organisms that are left on surfaces.

A new study published in the Lancet looking at five of six family members with the virus said the it’s spreading from person to person, rather than exclusively from animals or infected food, and can be transmitted in social, family and even hospital environments. It also now being spread by people who have not been to Wuhan. “This is a novel coronavirus, which is closest to the bat severe acute respiratory syndrome (SARS)-related coronaviruses found in Chinese horseshoe bats.”