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The U.S. Centers for Disease Control and Prevention (CDC) is warning of a public health situation representing an epidemiological nightmare. Three powerful germs are converging this season: influenza, COVID-19, and respiratory syncytial virus (RSV).

The influenza (flu) virus circulates at this time of year in the northern hemisphere. Typically, the flu spreads gradually during this season, rising to a peak in cases in January and February. However, this year it began to spread early. The circulating strain is called “H3N2,” a variant known since 1968, which tends to cause more severe cases.

What happens in the southern hemisphere in terms of the spread of influenza generally indicates what will happen north of the equator. And this season, the flu came up to two months earlier in several countries, such as Australia, causing more cases and more severe cases, in what was called the worst influenza season in years.

In a normal season, RSV circulates in autumn and winter without triggering warning signs. But experts say the rise in cases this year may be because the virus has found a more vulnerable population of infants and children, since they were not exposed to the virus because they were in lockdown during the pandemic, and they therefore have less immunity.

For the same reason, pregnant women were not exposed to RSV, as they would have been in a normal situation, and they did not pass on natural immunity to their babies.

In the case of COVID, it is clear that this coronavirus is here to stay, and new variants are circulating. Doctor David Ho, director of the Aaron Diamond Aids Research Center at Columbia University, and his team of researchers presented an overview of COVID-19 strains to add to the list.

These variants, named BQ.1, B.Q.1.1, XBB, and XBB.1, all evolved from Omicron, are capable of evading both vaccine-derived immunity and the body’s natural immunity created after infection. The degree of vulnerability depends on how many vaccinations the person has received, whether they received boosters, and whether they got COVID-19.

Most people who get the flu will recover within a period of a few days to less than two weeks. However, some may develop complications (pneumonia, for example) as a result of the flu, some of which can be life-threatening.

Sinus and ear infections are examples of moderate complications of the flu, while pneumonia is a serious complication. 

Other possible severe complications triggered by the flu may include:

• inflammation of the tissue surrounding the heart (myocarditis),
• inflammation of brain tissue (encephalitis),
• inflammation of muscle tissue (myositis), 
• and multi-organ failure (kidney failure and respiratory failure).

An infection of the respiratory tract by the flu virus can trigger an inflammatory response in the body and can lead to sepsis. 

The flu can also worsen other chronic health problems. For example, people with asthma may have asthma attacks while they have the flu, and people with chronic heart disease may have their condition exacerbated by the flu, according to the CDC.

RSV, on the other hand, usually causes cold-like symptoms and goes away on its own within a week or two. However, in infants and young children, and in older people with weakened immune systems or pre-existing conditions, it can cause a serious lung infection.

As explained by the CDC, people infected with RSV are usually contagious for three to eight days. However, some infants and people with weakened immune systems may continue to spread the virus even after they no longer show symptoms, for up to four weeks. 

Children are often exposed to and infected with RSV outside the home, such as at school or in day care centers, especially because of the vulnerability created by the COVID-19 pandemic. They can then transmit the virus to other family members.

RSV can survive for many hours on hard surfaces like tables and crib rails. It also often survives on soft surfaces for shorter periods of time.

Beyond the new variants in circulation, other factors come into play when predicting a new wave of COVID-19, including the following:

• The new strains that scientists are studying have spike protein mutations that are capable of neutralizing antibodies.
• The circulation of the virus is facilitated now that most people have returned to their normal activities, including group activities.
• In addition, during winter, there are more gatherings of people indoors.
• Most social spaces, and other spaces, no longer require the use of face masks.
• While vaccination campaigns stopped the first strains, the vaccination rate is lower for boosters. 

Influenza, RSV, and COVID share symptoms, including some symptoms affecting the upper respiratory tract, and modes of transmission. They also share their targets — those they infect most easily:

• People 65 years old and older,
• people of any age with certain chronic conditions (such as asthma, diabetes, heart disease, or lung disease), 
• people with diseases compromising the functioning of their immune system,
• pregnant women,
• and children under five years of age, but especially children under two years of age and premature infants.

What can happen when these three microorganisms come together? Do they fight over the same population group?

Some experts are talking about a “tripledemic,” a scenario where each virus is competing with the others. Others doubt that COVID and the flu circulate simultaneously with the same level of transmissibility, due to a phenomenon known as “viral interference,” which occurs when infection with one virus reduces the risk of contracting another. In fact, this is what probably happened with the drop in flu cases under lockdown during the COVID pandemic.

But now the rules are different, because societies have opened up again to return to “normality” and the public health barriers imposed to control the virus are no longer in place.

Therefore, everyone agrees that measures must be taken to weaken and limit the spread of these germs. The measures for all three viruses are: staying home if the person is sick, talking to your doctor, wearing a mask in closed or crowded places, not sharing utensils, and washing hands frequently.

In the case of the flu and COVID, vaccination is the best form of individual and collective protection. The flu is a seasonal infection, so the best way to prevent it is to get vaccinated every year. The virus that causes it is constantly changing, so scientists have to reformulate the vaccine to make it effective every year. People should be vaccinated when recommended by health officials, since it usually takes two weeks from the time of the shot for the immune system to achieve maximum protection.

The same rule applies for COVID. Vaccination remains the best way to stop the coronavirus, as seen during the wave of infections after Omicron, which were mild compared to the attack of the Delta variant.

In addition, vaccines continue to fulfill their main function: preventing severe disease and hospitalization from COVID, especially in the elderly or people with pre-existing conditions.

There is no vaccine against RSV. Maintenance treatment is carried out to keep the person comfortable until the body eliminates the virus from their body. Patients can:

• Bring down their fever and reduce pain with over-the-counter fever and pain reliever medicine, such as paracetamol or ibuprofen. (Children should never take aspirin).
• Drink enough fluids. It is important for people with RSV infection to drink enough fluids to prevent dehydration (loss of body fluids).
• RSV can cause more serious infections such as bronchiolitis, an inflammation of the small airways in the lungs, and pneumonia, an infection of the lungs. It is the most common cause of bronchiolitis and pneumonia in children under one year of age.

Healthy adults and infants infected with RSV generally do not need to be hospitalized. 

But the most vulnerable may need hospitalization if they have trouble breathing or are dehydrated. In severe cases, a person may require additional oxygen or intubation, with mechanical ventilation. In most of these cases, hospitalization lasts only a few days.

A drug called palivizumab is available to prevent severe RSV disease in certain high-risk infants and children. This medicine can help prevent severe RSV disease, but it cannot help cure or treat children who already have severe RSV disease, and it cannot prevent infection.

This story was produced using content from the original study and from other medical research, as well as health and public health sources, highlighted in related links throughout the article.