As health officials report a surge of winter viruses, health experts are warning that heart disease symptoms can sometimes mimic respiratory illnesses.

Four viruses are circulating in the U.S., sparking concerns of a possible "quademic."

Respiratory syncytial virus (RSV), influenza, COVID-19 and norovirus are all at "very high levels" around the country, experts warn. 

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The American Heart Association (AHA) confirmed that certain viruses have been linked to increased risk of heart attack and stroke. 

"The highest risk is within three days of infection, but remains heightened for up to 90 days," the AHA stated on its website.

Johanna Contreras, M.D., a cardiologist at Mount Sinai Fuster Heart Hospital in New York City, said she has seen people mistaking virus symptoms for serious heart complications.

Some patients who experience shortness of breath, wheezing, coughing, swelling and palpitations may assume their symptoms are linked to a cold when these could be signs of heart failure, she said in a release sent to Fox News Digital.

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Weakness, fever, dizziness and chest pain could also mask potentially life-threatening conditions.

Those may include pulmonary embolism (blood clot in the lungs), heart attack, pericarditis (inflammation around the lining of the heart), heart failure or viral myocarditis (inflammation of the heart muscle), according to Mount Sinai cardiologists.

Viruses can provoke an inflammatory condition, which can lead to or worsen cardiac conditions, according to Dr. Icilma Fergus, director of cardiovascular disparities for the Mount Sinai Health System in New York City.

"Typically, those [viruses] that make one sicker and promote a hypercoaguable state (an increased tendency to form blood clots) are more dangerous," she told Fox News Digital. 

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"The focus has now been increasingly placed on RSV and norovirus on top of the known influenza and COVID viruses."

Anuradha Lala, M.D., another cardiologist at Mount Sinai in New York City, noted that the body’s immune system creates an inflammatory response to fight and eliminate the virus — but this inflammation could inadvertently harm cardiac tissue. 

"If you have a known heart condition, viral infections can bring on exacerbations — or a worsening of the underlying tissue — whether it is atrial fibrillation, coronary heart disease or heart failure," she noted in the release.

A recent patient at the hospital recently experienced severe shortness of breath, weakness, palpitations and fatigue, fearing they had heart failure, she noted. 

"After they had bloodwork taken, there was a frantic moment when we could not reach the patient to share results that revealed a significantly elevated troponin level, which can be linked to a heart attack," she shared in the release. 

"Although we suspected the worst, we eventually reached the patient and they were hospitalized with influenza A and severe viral myocarditis. They were treated appropriately and luckily there was a good outcome."

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Older adults — as well as those who are immunocompromised or have a history of heart issues or other underlying conditions — are particularly at risk for cardiac complications, according to the Mount Sinai cardiologists. 

"Anyone is susceptible, even healthcare providers — and anyone who is not paying attention to their symptoms may get sick with potentially life-threatening complications," Fergus said in the report.

Patients who notice persistent chest pain and palpitations after a viral illness should consider ruling out myocarditis, which is inflammation of the heart muscle, according to Contreras.

It is important to discuss any post-virus symptoms with a healthcare professional, especially for those in high-risk groups, health experts told Fox News Digital.

Specific symptoms that warrant emergency attention include chest pain, difficulty breathing or staying awake, feelings of passing out, or extremes of blood pressure.

Swelling of the legs may also be linked to cardiac events — especially if there is also an underlying heart condition or risk factors such as obesity, diabetes or a family history of heart disease, Lala stated in the Mount Sinai release.

During the cold, damp winter months, certain viruses may thrive and become more virulent, Fergus told Fox News Digital. 

"People should stay vigilant and observe for symptoms of an impending cold," she advised. "Get tested to know what virus you have, as the antiviral treatments are different."

People should take measures to avoid exposure to winter illnesses and seek treatment if they become ill, especially if they have an underlying condition, Fergus advised.

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It is recommended that those who are in vulnerable groups get vaccines when available, the cardiologist added.

The American Heart Association recommends following the below precautions to reduce the chances of contracting a virus: 

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Heart disease remains the leading cause of death in the U.S., according to the American Heart Association.

An Ebola outbreak has been reported in the Democratic Republic of the Congo (DRC).

At least a dozen cases of the hemorrhagic fever have been reported in the Bolamba health zone, which is located in the Équateur Province in the DRC. Eight deaths have been reported.

Colomba Mampuya, president of the Red Cross/Ecuador committee, reportedly shared the information with media on Jan. 27.

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Meanwhile, the neighboring country of Tanzania has been grappling with an outbreak of Marburg fever.

"This is an unusually high death rate, even for Ebola," said Jacob Glanville, CEO and president of biotechnology company Centivax in San Francisco.

"This suggests either that more active cases have been identified, or that this strain is more lethal than average for prior strains, or that medical care was unusually poor for these subjects," he told Fox News Digital. 

The cases were identified in isolated villages, which improves the odds of outbreak isolation and increases the chance that medical care was substandard, Glanville noted. 

"However, biopsy samples should immediately be sequenced to rule out a new and potentially more lethal form of Ebola," he said.

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Samuel Scarpino, director of AI and life sciences and professor of health sciences at Northeastern University in Boston, reiterated that the ongoing situation in rural DRC is "quite serious."

"While the risk of widespread transmission is likely low, local impacts could still be substantial," he told Fox News Digital. 

"It is essential that the international community provides medical and public health support to DRC and that vaccines be made quickly available in both the affected and surrounding areas."

Both experts agreed that the U.S. is not at risk.

"Because Ebola only spreads from symptomatic individuals, the risk that a traveler could spark a small cluster of cases outside of DRC is very low," Scarpino said.

"We will be watching the situation closely, but currently, the risk to the U.S. is incredibly low."

Ebola occurs when someone is infected with orthoebolavirus zairense, which is a virus mainly found in sub-Saharan Africa, according to the Centers for Disease Control and Prevention (CDC).

The virus was first discovered in 1976 in the DRC.

The resulting disease is life-threatening, causing death in up to 90% of cases.

Initial symptoms of Ebola disease include "dry" symptoms like fever, aches, pains and fatigue, the CDC stated.

As the disease progresses, the person may experience "wet" symptoms like diarrhea, vomiting and unexplained bleeding.

Symptoms usually begin within eight to 10 days of exposure, according to the same source.

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The sickness is spread through contact with bodily fluids from someone who has been infected. 

In rare cases, it may spread from contact with an infected animal.

The best ways to prevent infection are to avoid contact with bodily fluids of infected people, to wear the proper protective equipment in high-risk environments, and to monitor for symptoms to ensure timely medical attention.

There are two FDA-approved medications (monoclonal antibodies) available to treat Ebola disease: mAb114 (Ansuvimab, also known as Ebanga) and REGN-EB3 (Inmazeb).

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Patients should also receive supportive care, including fluids and electrolytes, medicine to treat symptoms and any necessary treatment for infections, according to the CDC.

A child in California is presumed to have H5N1 bird flu, according to the San Francisco Department of Public Health (SFDPH).

As of Dec. 23, there had been 36 confirmed human cases of bird flu in the state, according to the California Department of Public Health (CDPH).

This represents more than half of the human cases in the country.

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The latest pediatric patient, who lives in San Francisco, experienced fever and conjunctivitis (pink eye) as a result of the infection.

The unnamed patient was not hospitalized and has fully recovered, according to the SFDPH.

The child tested positive for bird flu at the SFDPH Public Health Laboratory. The U.S. Centers for Disease Control and Prevention (CDC) will perform additional tests to confirm the result.

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It is not yet known how the child was exposed to the virus and an investigation is ongoing.

"I want to assure everyone in our city that the risk to the general public is low, and there is no current evidence that the virus can be transmitted between people," said Dr. Grant Colfax, director of health, in the press release. 

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"We will continue to investigate this presumptive case, and I am urging all San Franciscans to avoid direct contact with sick or dead birds, especially wild birds and poultry. Also, please avoid unpasteurized dairy products." 

Samuel Scarpino, director of AI and life sciences and professor of health sciences at Northeastern University in Boston, is calling for "decisive action" to protect individuals who may be in contact with infected livestock and also to alert the public about the risks associated with wild birds and infected backyard flocks. 

"While I agree that the risk to the broader public remains low, we continue to see signs of escalating risk associated with this outbreak," he told Fox News Digital.

Experts have warned that the possibility of mutations in the virus could enable person-to-person transmission.

"While the H5N1 virus is currently thought to only transmit from animals to humans, multiple mutations that can enhance human-to-human transmission have been observed in the severely sick American," Dr. Jacob Glanville, CEO of Centivax, a San Francisco biotechnology company, told Fox News Digital.

"This highlights the requirement for vigilance and preparation in the event that additional mutations create a human-transmissible pandemic strain."

As of Jan. 10, there have been a total of 707 infected cattle in California, per reports from the California Department of Food and Agriculture (CDFA).

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In the last 30 days alone, the virus has been confirmed in 84 dairy farms in the state.

Cases of tularemia, also known as "rabbit fever," are on the rise in the U.S., according to a new report from the Centers for Disease Control and Prevention (CDC).

Caused by the bacteria Francisella tularensis, the disease commonly infects rabbits, hares and rodents. However, it is zoonotic, which means it can spread from animals to humans.

The bacteria is a "tier-1 select agent," a classification given to agents and toxins that "present the greatest risk of deliberate misuse with significant potential for mass casualties or devastating effects to the economy, critical infrastructure or public confidence, and pose a severe threat to public health and safety," per the CDC. 

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Although tularemia is relatively rare, with only 2,462 diagnoses between 2011 and 2022, cases have risen 56% compared to the prior decade (2001 to 2010), as reported in the CDC’s Morbidity and Mortality Weekly Report.

"Increased reporting of probable cases might be associated with an actual increase in human infection, improved tularemia detection or both," the report states.

Daniel Ruderfer, M.D., chief of the Division of Pediatric Infectious Diseases at Hackensack Meridian K. Hovnanian Children's Hospital in New Jersey, believes that the increase in cases is mostly due to improved microbiology detection methods.

"The traditional method of confirming cases has historically been via growth in culture and antibody testing," he told Fox News Digital. 

"However, newer detection methods, such as PCR testing, are likely a major contributor to the increase in reported cases."

Humans can contract the disease through bites from deer flies or ticks, contact with infected animals, or exposure to contaminated water or aerosols, the same source stated.

Symptoms of tularemia can vary depending on the type of disease.

General symptoms include chills, headache, malaise, fatigue, anorexia, myalgia, chest discomfort, cough, severe sore throat, vomiting, diarrhea, and abdominal pain, according to Ruderfer.

"Depending on the location of the infected bit or scratch, people can develop localized lymphadenopathy (enlarged lymph nodes) and a cutaneous ulcer at the infection site," he said. 

"Other manifestations include conjuctivitis, pneumonia and potentially even bloodstream infections."

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The death rate from the disease is typically low, less than 2%, but the CDC noted that it can be as high as 24% in rare, severe cases.

Tularemia can be treated with antibiotics, but no vaccine is currently available.

"The infection is absolutely dangerous and potentially life-threatening if not treated with appropriate antibiotics," said Ruderfer.

Those most at risk include children between 5 and 9 years of age, older men, American Indian and Alaskan Native people, and those living in central U.S. states, according to the report.

The general population is not at an "obvious" risk for infection unless they come into physical contact with an infected rabbit, tick or deer fly, the expert noted. 

Those who hunt or interact routinely with rabbits should see a doctor if they develop any concerning symptoms, he advised.

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"Many factors might contribute to the higher risk for tularemia in this population, including the concentration of Native American reservations in central states and sociocultural or occupational activities that might increase contact with infected wildlife or arthropods," the CDC wrote.

The patient in Louisiana who was hospitalized with severe bird flu illness was found to have a mutated version of the virus, the U.S. Centers for Disease Control and Prevention (CDC) announced last week.

The fact that the virus mutated within the patient suggests that it could potentially spread from human to human.

The CDC analyzed samples of the H5N1 virus that were collected from the patient, comparing its genomic sequences to those of infected dairy cows, wild birds, poultry and other animals, the agency stated.

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"The analysis identified low frequency mutations in the hemagglutinin gene of a sample sequenced from the patient, which were not found in virus sequences from poultry samples collected on the patient’s property, suggesting the changes emerged in the patient after infection," the CDC said.

"While these low frequency changes are rare in humans, they have been reported in previous cases of A(H5N1) in other countries and most often during severe disease."

Based on the discovery of these genetic changes in the virus, health officials recommend performing "ongoing genomic surveillance" in people and animals, taking steps to contain bird flu outbreaks among dairy cattle and poultry, and taking steps to prevent transmission when exposed to infected animals or environments.

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The CDC maintains that the risk to the general public is still low.

"The same mutations were not present in viral genomes sampled from the backyard birds that presumably infected the individual," Samuel Scarpino, director of AI and life sciences and professor of health sciences at Northeastern University in Boston, confirmed to Fox News Digital. 

"Because the mutations were present in the human patient, but not the backyard birds, this suggests that the mutations arose during the course of that individual’s infection."

Dr. Marc Siegel, clinical professor of medicine at NYU Langone Health and Fox News senior medical analyst, told Fox News Digital, shared his thoughts on the significance of this finding.

"It is somewhat concerning that the H5N1 bird flu virus found in the Louisiana patient showed a mutation that allowed it to enter the upper airways more easily in this patient, but this mutation has been seen before," he told Fox News Digital.

The good news, the doctor noted, is that there have not been any reports of the Louisiana patient transmitting the virus to other humans.

"We know the mutations to look out for in terms of the potential to spread among humans" based on previous research, Siegel said. 

"It is important that surveillance among domestic poultry and dairy cattle is extensive," he added. 

Scarpino agreed that while the mutations are "concerning," they "likely do not represent an increased risk to the public."

"Similar events — mutations arising during infection that increase risk in humans — occurred with the individual who was infected with H5N1 from wild birds in Canada and have happened a number of times during previous H5N1 outbreaks outside the U.S. and Canada," he told Fox News Digital. 

"To date, it does not appear as though the individual in Louisiana transmitted the infection to other people."

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The doctor cautioned, however, that the more opportunities the virus has to infect people, the more likely similar mutations will occur and spark a "chain of transmission" in humans. 

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"Each human infection represents a spin of the epidemic roulette wheel," Scarpino said. 

"We need to take active steps to eliminate H5N1 infections in agricultural populations and better understand why so many wild birds continue to be infected."

Travel is a big part of the holiday season, with statistics showing that more than 119 million Americans plan to embark on some type of journey between Christmas and New Year's.

Unfortunately, traveling also increases the risk of getting sick — but there are steps you can take to increase your chances of staying healthy while away from home.

"When you're traveling, when you're on the road, there's a lot of risk of stress and disorientation," Dr. Marc Siegel, clinical professor of medicine at NYU Langone Health and Fox News senior medical analyst, told Fox News Digital.

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"You're not in your usual habitat, and that can make people disoriented, upset, anxious or even sleep-deprived, especially when changing time zones."

Siegel shared some of his top tips for preventing illness during holiday travel.

Staying hydrated has been shown to boost the immune system and protect against illness.

Water is always best, but other hydrating fluids include plain coffee or tea, sparkling or flavored waters, 100% vegetable juice, and milk or milk alternatives.

It’s best to travel while "well-exercised," Siegel said.

"If you have a regular exercise routine, I wouldn't suspend it a week before travel," he said.

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"If you're regularly exercising, sleeping right and eating right before you go, I think that that puts you in much better shape when you're traveling."

Siegel said he’s a "big believer" in wiping down surfaces, especially when traveling by plane.

"You wouldn't believe what these surfaces carry — we've studied that," he said. "There are a lot of germs in that tray table, and it's the person next to you who could be sick." 

"When you're about to take a trip, it is a good time for you to think about whether you’re up-to-date on your vaccines," Siegel said.

One immunization that isn’t given enough attention, according to the doctor, is Tdap, a combination vaccine that protects against tetanus, diphtheria and pertussis (whooping cough).

It is given at least once every five to 10 years.

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"There's a ton of whooping cough around this year," Siegel said. "Thousands of cases are reported, but many thousands aren't."

The doctor also recommends the shingles shot for those over the age of 50 and the pneumonia vaccine for people 60 and older.

"When you're under stress from travel, that might be when you could get sick," Siegel said, as the immune system isn't functioning at an optimal level. 

"That's when shingles might reappear," he warned. "Shingles is actually a chickenpox virus that's dormant in your body for years, but can recur at times of stress."

The Centers for Disease Control and Prevention (CDC) also recommends that everyone 6 months and older receives COVID and flu vaccinations, with rare exceptions.

For those who take multiple daily medications, the doctor recommends traveling with one pill bottle and putting the various pills in it, making it less likely for any to get misplaced.

"Make sure you have more than enough," he advised. "You never know when you're going to get delayed, especially around holiday travel."

Siegel recommends bringing three or four extra days of pills for all medications.

"Depending on what chronic illnesses you may have, it's a good idea to be up-to-date with blood draws and visits to your doctor" before traveling, he added.

It can be challenging to maintain a regular sleep cycle while traveling, Siegel noted, especially when time zones are changing.

"The more you can catch some winks while traveling, the better off you're going to be," he said.

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For those who have trouble falling asleep while on the road, Siegel recommends identifying what makes you drift off at home and using those same techniques.

"I get asked a lot for sleeping aids," he said. "For people who are traveling on long trips, I personally am uncomfortable giving medication if the patient hasn't been taking it already."

While masks "got a bad name" during the pandemic because of mandates, Siegel noted that they are tools that can be used for those who are ill or at a higher risk. 

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"If you're a person who’s at risk of an infectious disease or has a chronic illness, the last thing you need is to get the flu, COVID or RSV."

The doctor recommends considering a mask for tight spaces where there are a lot of people around.

"You don't know what they have or what they are harboring," he said.

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"That's why I would consider one, especially if you're at high risk."

Overall, Siegel said, "staying hydrated, eating right and sleeping properly as best as possible is the way to go in decreasing stress while traveling."