T.S. Eliot might have famously called April “the cruelest month.” But data from the Centers for Disease Control and Prevention (CDC) shows that it is in fact January that deserves the honor.

More people die in Southern California during January than any other month, according to CDC data that shows the number of deaths and their causes over the last five years.

Within Januaries from 2013 to 2017, 46,962 people died in California. December comes in second at 44,219 deaths. March and February are third and fourth with 42,620 and 40740 deaths respectively.

Here are the top five causes of deaths during January:

— Atherosclerotic heart disease (hardening or blocking of the arteries): 4,653

— Alzheimer’s disease: 3,127

— Lung cancer: 2,208

— Heart attack: 2,314

— Chronic obstructive pulmonary disease (COPD): 2,239

These numbers beg the question: Why are the winter months so dangerous? And why is January the deadliest?

No straight line can be drawn between cause and effect to explain this phenomenon. Yet doctors and medical professionals who see these numbers manifesting in the form of crowded emergency rooms and deceased patients admit: It gets pretty bad in January.

Flu a factor?

A majority of individuals in January might have died from heart and lung issues.

But people with these types of underlying health conditions might get into serious trouble if they are also stricken by the flu, said Dr. Salvador Hernandez, chief of the infectious diseases department at Kaiser Permanente Orange County.

“If you are an elderly person with heart disease or COPD and get the flu, it could get really complicated,” he said.

The flu, Hernandez says, might be just what causes the January bump when it comes to fatalities in Southern California.

He says he starts seeing emergency rooms and hospitals get really crowded by mid-January.

“There may be many reasons for this increase,” Hernandez said. “Large numbers of people are traveling during the holidays. People are gathering in closed areas — malls, homes, airports. It could take up to seven days for flu symptoms to surface.”

Just in the last two weeks, two people have died in Orange County from the flu, Hernandez said, adding that the most recent victim was a 48-year-old man.

When you combine all these factors with how people don’t take care of themselves during the holidays, the consequences can be deadly, he said.

“You tend to put off that doctor’s visit for after the holidays,” Hernandez said. “People are pretty busy during the holidays and usually aren’t paying attention to their health.”

‘A little bit of a bump’

Los Angeles County sees an uptick in deaths this time of year as well, said Dr. Jonathan Lucas, the county’s Medical Examiner.

“We get only a small percentage of the natural deaths,” he said. “But, even then, we see a little bit of a bump.”

Lucas said he’s noticed the January increase not just in Los Angeles County, but also in San Diego where he recently served as chief deputy medical examiner.

January is also prime time when it comes to other communicable diseases such as measles and whooping cough, said Dr. Alexandra Clark, division chief for general pediatrics at Loma Linda University Health.

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Q&A: Science, politics and the worst pandemic in 100 years Getting vaccinated against virus-caused diseases such as influenza, measles and whooping cough is the best form of prevention, she added.

“There’s nothing in life that doesn’t have a risk and vaccines have a slight risk, too,” she said. “But the risk of falling sick and experiencing a significant complication from the infection is far greater than any risk factor posed by the vaccine itself.”

Hernandez agrees, saying vaccination is the only way “we can make a dent.”

“It’s not perfect, but it’s the best way,” he said. “A seat belt may not save your life in a major accident, but it will save you in a minor collision. The flu vaccine is similar. It’s better than nothing.”

Data reporter Nikie Johnson contributed to this story.