“We have never seen so many cases in the spring”

Positivity for SARS-CoV-2 in primary health care settings increased almost 8 times in just four weeks: from 2.2% in the first week of May to 17.1% in the last, according to the latest report of the Acute Respiratory Infections Surveillance System coordinated by the Carlos III Institute of Health.

This percentage is similar to the percentage seen by Covid last fall and early winter, when it contributed to the traditional collapse of medical centers around this time. On the other hand, the estimated incidence doubled in two weeks, from 33.5 cases per 100,000 people to 74.8.

Since the start of 2024, incidence has remained low, neither completely disappearing nor recovering, with an overall positive rate of 8.4% in the 2023–24 season.

“There is growth,” he admits. Angela Dominguez, Coordinator of the Vaccine Group of the Spanish Society of Epidemiology. “What happened was we were at a very low level. Even if it increases a little, it will grow significantly. But it warns us of the importance of maintaining constant vigilance.”

In contrast, the flu positivity rate is 1.5% and the estimated incidence is 6.6 cases per 100,000 inhabitants, which has been at the baseline level for several months.

However, four years after the emergence of SARS-CoV-2 It is still difficult to distinguish flu from Covid by eye. “There are some characteristics that are more typical of Covid,” Dominguez admits, “but all respiratory tract infections are similar, so they are seen together.”

The Acute Respiratory Disease Surveillance System collects data on the frequency of various symptoms, and while cough and general malaise are very common with both flu and Covid, fever is more common with the former than with the latter.

Yes, the virus differs in its behavior. As influenza and RSV return to their classic seasonality, coronavirus continues to appear at the most unexpected times: spring and summer.

“Just as the influenza virus lasts longer in winter, which is compounded by staying indoors and worse ventilation, this does not happen with SARS-CoV-2,” says the epidemiologist.

Primary care departments are starting to get used to treating colds in the spring. “We’ve never lived so much in this era,” he admits. Isabel Gimenofamily physician at the Isla de Osa Medical Center (Madrid) and representative of the Spanish Society of General Practitioners and Family Physicians (SEMG).

The doctor explains that diagnostic tests are only performed on older people, so “we don’t know very well what the burden of the disease is.” According to Carlos III, the greatest positivity this season is among adults aged 45 and 64 (11.9%) and over 65 (11%).

“You can intuitively predict when a person has Covid, but not be sure,” Gimeno says. “Today I saw an 80-year-old woman with a cold and she has smelled like Covid since she came in: we tested her and she tested positive. “Influenza is now seen less frequently in older people.”

Even (temporary) loss of smell is no longer a hallmark. Carlos III estimates that anosmia occurs in 5.4% of people with Covid, compared with 4.8% of those who contracted the flu.

Options and vaccines

SARS-CoV-2 is not only increasing its presence in primary care consultations. The positivity rate for the virus among those hospitalized for the respiratory infection is 25.4%, doubling in just two weeks. However, for influenza the figure is 0.7%.

Hospitalization rates are estimated to have increased from 2.2 cases per 100,000 residents to 3.6. 29.7% of Covid hospitalizations are due to pneumonia, 4.2% of intensive care unit admissions and 8.2% of deaths.

51% of those hospitalized with Covid have high blood pressure. It is the most common comorbidity, followed by metabolic diseases such as diabetes (43.1%), cardiovascular diseases (41%) and respiratory diseases (40.6%).

The most identifiable variant in both primary and hospital care is BA.2.86, with mostly sublineages classified as JN.1 in more than 80% of cases at both levels of care.

The World Health Organization (WHO) announced in April that new Covid vaccines for next season should be based on the variant, “although We are observing the growth of two sub-options: KP.1 and KP.2.“, comments the family doctor.

“The FDA is still debating whether to recommend a JN.1 or a KP.1 vaccine,” he notes. Both are subvariants of BA.2.86, which is a subvariant of Omicron.

In contrast, XBB.1.5 and similar variants, which were most common in the fall (and for which the latest messenger RNA vaccines were developed), have been in the minority for months.

“Vaccination recommendations will likely remain the same in terms of the population they target,” Gimeno says. This, people over 60 years of age or people younger but with risk conditionspregnant women and essential public service personnel, such as health workers or police.

Angela Dominguez agrees. “Obviously, vaccination will be very important for people over 60 and with underlying health conditions. As for the rest of the population, we still have to see.”