Female Aedes aegypti mosquito as she was in the process of obtaining a "blood meal." (credit: US Department of Health and Human Services )

Puerto Rico has declared a public health emergency amid an ongoing outbreak of dengue infections, a mosquito-spread viral infection that can cause fever, aches, rash, vomiting, and, in about 5 percent of cases, a severe disease marked by internal bleeding and shock.

The US territory has tallied 549 cases since the start of the year, representing a 140 percent increase compared with cases tallied at this point last year, according to the territory's health department . The Associated Press reported that more than 340 of the 549 cases have been hospitalized.

In 2023, the island nation of more than 3.2 million people had over 1,000 cases of dengue throughout the year.

Enlarge / A brightly colored transmission microscope image of measles viruses. (credit: Getty | BSIP )

A team of health experts from the Centers for Disease Control and Prevention arrived in Chicago Tuesday to help respond to a flare-up of measles cases at a migrant shelter in the city's Pilsen neighborhood, according to CNN .

So far, there have been four cases identified at the Halsted Street shelter: two young children, one recovered and one hospitalized in good condition as of March 10; and according to an announcement on Monday, March 11 , two adults who were reported in good condition.

The four cases come just days after the city's health department announced a measles case in a Chicago resident with no recent travel outside of the city and no reported connection with the shelter. The case, announced on March 7 , was the first measles case identified in the city since 2019, officials noted. It remains unclear how that resident contracted the highly infectious virus, though the health department noted that the person had been in contact with domestic and international travelers. The person was said to be recovering well at home, and their infectious period ended on March 6.

Enlarge / An electron micrograph of norovirus. (credit: Getty| BSIP )

Officials in Alabama have shut down an elementary school for the rest of the week and are conducting a deep clean after 773 of the school's 974 students were absent Wednesday amid an explosive outbreak of gastrointestinal illness.

Local media reported that only 29 students were absent from Fairhope West Elementary School on Tuesday. However, the situation escalated quickly on Wednesday as word spread of a stomach bug going around the Gulf Coast school. A spokesperson for the county school district told AL.com that 773 students and 50 staff were absent Wednesday. It's unclear how many of the absences are due to sickness or precaution.

Health officials are now investigating the cause of the gastrointestinal outbreak, collecting specimens for testing. So far, officials are working under the assumption that it is norovirus, a highly infectious gastrointestinal bug that can survive hand sanitizer and transmit easily from surfaces, food, and water. The symptoms of the unidentified illness align with norovirus: vomiting, diarrhea, abdominal cramps, and nausea.

Enlarge / A child with measles. (credit: Greene, Charles Lyman )

Florida health officials on Sunday announced an investigation into a cluster of measles cases at an elementary school in the Fort Lauderdale area with a low vaccination rate, a scenario health experts fear will become more and more common amid slipping vaccination rates nationwide.

On Friday, Broward County Public School reported a confirmed case of measles in a student at Manatee Bay Elementary School in the city of Weston. A local CBS affiliate reported that the case was in a third-grade student who had not recently traveled. On Saturday, the school system announced that three additional cases at the same school had been reported, bringing the current reported total to four cases.

On Sunday , the Florida Department of Health in Broward County (DOH-Broward) released a health advisory about the cases and announced it was opening an investigation to track contacts at risk of infection.

Enlarge / This thin section transmission electron microscopic (TEM) image reveals numerous spheroid-shaped Enterovirus-D68 (EV-D68) virions. (credit: CDC/ Cynthia S. Goldsmith, Yiting Zhang )

2022 was the bad year that wasn't—at least for a mysterious paralyzing condition in children.

In the decade before, hundreds of young, healthy kids in the US abruptly felt their limbs go weak. Debilitating paralysis set in. In recent years, around half of affected children required intensive care. About a quarter needed mechanical ventilation. A few died, and many others appear to have permanent weakness and paralysis.

Researchers quickly linked the rare polio-esque condition to a virus known for causing respiratory infections, often mild colds: enterovirus D68, or EV-D68 for short. Identified decades ago, it's a relative of polio, one of the over 100 non-polio enteroviruses that float around. But when EV-D68 began surging, so did the mysterious paralyzing condition, called acute flaccid myelitis, or AFM. The menacing pair seemed to come in waves every other year, likely starting with a cluster of cases in California in 2012 . In 2014, there were 120 AFM cases in 34 states . In 2016, 153 cases in 39 states. In 2018, 238 cases in 42 states. By contrast, there were just a few dozen cases or so in each of the years in between, cases that were sporadic or unrelated to EV-D68.

Enlarge / A baby with measles. (credit: CDC )

The Centers for Disease Control and Prevention is putting clinicians on alert about the growing risk of measles cases and outbreaks amid a global surge in transmission .

In an outreach message sent Thursday , the CDC told clinicians to look out for patients who have a rash accompanied by a fever and other symptoms of measles, as well as patients who have recently traveled to countries with ongoing measles outbreaks .

Between December 1, 2023, and January 23, 2024, there have been 23 confirmed measles cases in the US, including seven direct importations by international travelers and two outbreaks with more than five cases each, the CDC noted. Most of the cases were in unvaccinated children and teens.

Enlarge / Parents with children who are suffering from respiratory diseases are lining up at a children's hospital in Chongqing, China, on November 23, 2023. (credit: Getty | Costfoto/NurPhoto )

Last week, news stories and a posting on an infectious disease surveillance system raised fears that another novel respiratory pathogen with pandemic potential was mushrooming in northern areas of China—namely Beijing and Liaoning province. The reports referenced " undiagnosed pneumonia " in " clusters " of children, hospitals that were "overwhelmed," and parents who were questioning whether "authorities were covering up the epidemic."

But, rather than a sequel to the COVID-19 pandemic, the situation appears to be merely a side effect of it. According to independent experts and the World Health Organization, it's most likely that China is now experiencing a roaring comeback of a mix of common respiratory infections that were muted during the global health crisis. Many other countries experienced the same surges in the past year or two, including the US. As with the other countries, the wave of infection in China is mostly affecting children, who were less exposed to all sorts of pathogens amid the health restrictions, leaving them more vulnerable to infections now.

The global explosion of COVID-19 transmission and subsequent pandemic health measures severely disrupted common cycles of many infectious diseases worldwide, knocking seasonal respiratory infections like adenoviruses and RSV (respiratory syncytial virus) off their annual cycles. In the US, the 2020-2021 flu season was virtually nonexistent, for instance. But, as the novel coronavirus abated and restrictions lifted, those pathogens vigorously returned. (The US also experienced early and intense peaks of RSV and flu last year.)

Enlarge / Travelers walk through Union Station as they travel ahead of the Thanksgiving holiday in Washington, DC, November 21, 2023. (credit: Getty | Saul Loeb )

As Americans prepare for the Thanksgiving holiday this week, respiratory viruses are ramping up, creating hazardously infectious conditions for mass travel and multi-generational family gatherings.

Flu is on the rise in most of the country, with six Southern states and the District of Columbia already seeing high levels of influenza-like illnesses (ILI) activity. Louisiana has reached "very high" ILI activity, the Centers for Disease Control and Prevention reported in the latest flu surveillance update . The percentage of flu tests coming back positive is also increasing nationwide, with only one region, the Mid-Atlantic region, showing a stable week-over-week positivity rate. But the CDC noted that its rate overall is trending upward.

This year's flu season is again starting early; the current flu activity levels are about four to six weeks ahead of when we usually see them. And with activity already at highs in many states, there's a good chance that we'll once again see extremely high levels in some places—moving from red to the dreaded deep purple on CDC's scale, which we saw last year.

Enlarge / A baby with measles. (credit: CDC )

The World Health Organization and the US Centers for Disease Control and Prevention are sounding the alarm over the global rise of measles cases, deaths, and outbreaks as vaccination rates struggle to recover from a crash during the COVID-19 pandemic.

Between 2000 and 2019, estimated worldwide coverage of the first dose of a measles-containing vaccine rose from 72 percent to 86 percent. But amid the global public health crisis in 2020, the vaccination rate fell to 83 percent, and then to 81 percent in 2021—the lowest since 2008.

According to a new joint report by WHO and the CDC published this week, coverage of first-dose measles vaccines recovered slightly in 2022, rising to 83 percent. But of 194 WHO countries, only 65 (34 percent) reached a target vaccination rate of 95 percent or above for the first measles vaccine. Further, two doses are needed to stop the disease, and the estimated coverage rate for two doses was only 74 percent in 2022, up from 71 percent in 2021. Overall, the gains in vaccination weren't enough to prevent a comeback from the highly contagious and sometimes deadly virus.