MONTREAL -- During a pandemic, feverish newborns need to receive proper attention from their parents, and particularly from health care professionals, warns a new study published by researchers at the Montreal Children's Hospital.

The extra vigilance is warranted, not because they may have been infected with the coronavirus, but because they may have a potentially life-threatening infection.

Typically, about 10 per cent of newborns with fever have a life-threatening infection; this percentage doubled to 20 per cent during the study period, from March 2020 to March 2021.

"There has been a decrease in the transmission of viral infections, due to health measures," said the study's lead researcher, Dr. Brett Burstein. With social distancing and everyone wearing masks, there was almost no influenza, rhinovirus, or other viruses that usually circulate.

"So when a baby came to the emergency room with a fever, the proportion that had significant bacterial infections went up a lot."

While the proportion of serious infections (such as bacterial meningitis, urinary tract infections and bacteremia) doubled, the number of emergency room visits to the Children's Hospital for feverish infants under three months of age decreased by two thirds.

Since the beginning of the pandemic, many people avoided going to emergency rooms out of a fear of catching the virus and to make room for others they supposed to be the "really sick" ones. At the Montreal Children's Hospital, there has been a 60 per cent decrease in visits to the ER.

Fever in a newborn under three months of age is always a concern, Dr. Burstein said.

"Newborns don't have a well-developed immune system and they don't have the benefit of vaccines," he explained. "So, already, we're talking about a vulnerable population as far as infections are concerned."

About 2 per cent of all full-term babies will be seen for fever in their first few months of life, and 90 per cent of these cases will be mild and require only minimal care.

However, between March 2020 and March 2021, the proportion of babies with fever who had meningitis or bacteremia (the presence of bacteria in the blood) jumped from 1 per cent to 3.5 per cent.

"This increase tells us that during the pandemic, during the health measures, we need to be especially careful with newborns who have a fever," said Dr. Burstein.

"There is a decrease in the number of feverish babies, with no decrease in significant infections."

The infections of greatest concern have not decreased at all, he added. So, when a baby has a fever during the pandemic and there are health measures in place, it's more likely to be something of concern than the normal viruses that are circulating. Even a urinary tract infection in a baby can turn into a serious health problem fairly quickly.

The message to parents and doctors is, therefore, very clear: be more careful than ever with a baby who has a fever during the pandemic and health restrictions.

Especially since feverish babies can be particularly difficult to diagnose, as they "trick" doctors into thinking they are quite well, even though they are actually very sick, Dr. Burstein said.

They look fine until the last moment, "and then they crash," he said. 

The findings were published in the medical journal JAMA Network Open.

This report by The Canadian Press was first published in French on July 15, 2021.