A dangerous winter virus outbreak in the United States is showing unusual persistence, even though it usually peaks during the winter and subsides at the end of March, prompting health authorities to take extraordinary measures.
According to federal data, the positivity rate for respiratory syncytial virus (RSV) tests was around 7.5%, compared to just 5% in the same period last year, reflecting higher than usual activity for this time of year.
Faced with this situation, several states decided to extend the vaccination period against the virus until at least April 30, in an unprecedented move aimed at keeping pace with the infection season continuing for a longer period than usual.
Wastewater monitoring data from the Centers for Disease Control and Prevention shows that about half the country is experiencing moderate levels of virus spread, with a clear concentration of cases in the Midwest and Northern Plains.
States such as Michigan, Minnesota, South Dakota, Wyoming, Iowa, Kansas, Nebraska and Vermont recorded the highest levels of spread, while moderate levels appeared in other states including California, Hawaii, Illinois, Louisiana, Nevada, New Mexico, Tennessee and West Virginia.
In contrast, more than 30 states, particularly in the South, Southwest and West Coast, are still recording low levels of the virus, including Florida, Texas, Colorado, Oregon, Virginia and Washington.
In explaining this unusual pattern, Dr. Robert Hopkins, medical director of the National Infectious Disease Foundation, said that the virus season was delayed this year and extended into the spring, a fact also confirmed by warnings from the Centers for Disease Control and Prevention indicating the possibility of continued high activity until April in several regions.
Despite this spread, indicators of pressure on the health system have begun to gradually decline, as visits to emergency departments and hospital admissions have decreased, but they remain high among children under the age of four.
Infants, especially those under eight months old, are the most vulnerable to complications, as the virus can lead to conditions such as bronchiolitis and pneumonia, and some cases may require the use of ventilators or oxygen, as explained by Dr. Yvonne Maldonado of Stanford University.
The data indicates that between 2 and 3 out of every 100 infants under three months are hospitalized annually due to the virus, while the number of admissions of children under five ranges between 58,000 and 80,000 cases, with between 100 and 300 deaths recorded.
Data from Minnesota — which has the highest levels of spread this season — also showed that the virus is currently causing more hospitalizations than the flu or COVID-19, although this year's peak was lower than the previous two seasons.
Regarding prevention, health authorities recommend vaccinating all infants born during the virus season, especially if mothers did not receive the vaccine during pregnancy or their vaccination status is unknown, in addition to giving preventive doses to some of the most vulnerable children between the ages of 8 and 19 months.
Extending the vaccination period allows doctors and hospitals to continue providing vaccines and antibodies for a longer period, while emphasizing the importance of protecting the most vulnerable groups.
The virus is not only dangerous for children, as the elderly, especially those with weakened immune systems, are more susceptible to serious complications, although symptoms in healthy adults are often mild and resemble a common cold.
It is estimated that the virus causes between 110,000 and 180,000 hospitalizations annually in the United States of people aged 50 and older, and can lead to severe respiratory illness or death.
Despite the availability of vaccines, vaccination rates among the elderly remain relatively low, with only about 38% of those aged between 60 and 74 years having received the vaccine, and the rate rising to 41.5% among those over 75 years of age, with a notable variation between regions and population groups.
