Spring is beautiful, but it may also be making you feel miserable.

Ticks are out in record numbers, pollen is everywhere, and the common cold is hitting its seasonal peak.

Meanwhile, an unusual hantavirus outbreak on a cruise ship sounds like a movie plot, but it’s a sharp reminder of why global health connectivity matters. I’ll walk you through what disease detectives are piecing together, answer a Covid vaccine question, and close with some good news.

Let’s dig in!

Disease weather report

Ticks keep on ticking–NORTHEAST LEADS IN TICK BITE ER VISITS

It’s an unusual year for ticks.

Emergency department (ED) visits for tick bites are running at roughly 114 per 100,000 people per week, nearly double the typical rate at this time in previous years (60-70 per 100,000).

The Northeast is bearing the brunt of it, with the Midwest running a close second.

It’s not clear whether this is just an earlier year or a worse year overall. Time will tell.

Data from CDC; Annotated by Your Local Epidemiologist.

ED data are a remarkable window into public health because data are quick, and so many Americans use emergency departments as their primary or urgent care.

Why are people going to the ED for a tick bite? Four main reasons:

1. They don’t know what to do. It’s hard to know whether a bite is dangerous, how long the tick has been attached, or what symptoms to watch for. When in doubt, people default to the place they know will help, and that’s the ED.
2. They can’t remove it safely on their own. Removing a tick incorrectly (such as burning it or smothering it with petroleum jelly) can cause it to release more saliva and, theoretically, increase the risk of infection. If someone can’t see it well, can’t reach it, or is too anxious to do it calmly, getting a clinician’s hands and eyes involved is helpful.
3. They need antibiotics. If a tick has been attached long enough in a high-risk Lyme area, a prophylactic dose of doxycycline is genuinely time-sensitive, though urgent care or a family doctor can handle it just as well.
4. They have symptoms that are emergencies, such as anaphylaxis or tick paralysis.

What this means for you: Prevention goes a long way. Most pathogens can only be transmitted after a tick feeds for some time, so call your physician if one has been attached more than 36–48 hours. Use tweezers for removal (the only recommended method). And remember: nymphs are the size of a poppy seed.

Feeling crummy? It’s likely the common cold and/or allergies

The common cold is approaching its spring peak while other respiratory viruses become dormant. If you’re feeling crummy right now, it’s probably a cold.

Percent of positive tests for respiratory viruses. Source: NREVSS; Annotated by Your Local Epidemiologist

Or it may not be a virus at all. Much of the U.S. is suffering from allergies, and allergy season is getting longer and more intense.

Plants are releasing pollen about 40 days earlier than they used to and stopping about two weeks later, thanks to rising temperatures. Higher CO2 levels mean more pollen per plant.

Pollen.com map

What this means for you: Check the pollen forecast, rinse your nose with saline (use distilled water), and shower before bed to wash pollen off.

For medication, go with second-generation antihistamines like Zyrtec over Benadryl (Benadryl has been around since the 1940s but carries more side effects.) Always check with your doctor. Also, here is a great room-by-room guide you may find useful.

Spotlight: What hantavirus and a cruise ship are reminding us

Over the weekend, news broke of a small but alarming outbreak aboard a cruise ship traveling from Argentina to South Africa: three deaths, one critically ill, and three additional suspected cases of hantavirus. (Two cases have been confirmed so far.)

Hantavirus kills 40–60% of those it infects, making it one of those viruses that would make a terrifying movie. While it is very rare, random cases do pop up—even in the U.S.—when rat droppings are aerosolized. (You may remember Gene Hackman’s wife, Betsy Arakawa, died last year in New Mexico.)

But this situation is unusual because multiple cases are suspected within a very confined space, and the ship is coming from Argentina, which is home to a particularly nasty strain of hantavirus. (More below.)

So disease detectives are working urgently to piece together what happened to these seven people, assess the risk to everyone else on that ship, and the risk to South Africa (and the world) waiting at the other end. Five questions, specifically, are worked in parallel:

• Are there more cases? The ship hasn’t been allowed to dock, and passengers are being asked to monitor symptoms. Unfortunately, the incubation period (how long the virus lives before symptoms arise) can be weeks.
• I can’t even imagine how terrified these poor passengers are because of the level of uncertainty.
  • This situation is ethically extremely tricky:
  • isolate the people on the ship that may contain an exposure source vs. deboard all 150 passengers and isolate them as best as possible. Deboarding comes with risks. The risk-benefit final decision is made by the cruise operator, the ship’s captain, the Cape Verde health authorities, the WHO, and the governments of the nationals on board.
• Where did it come from? Hantavirus lives in rodents. Did someone encounter infected droppings at a port stop in Argentina? Is there a rodent on the ship that is spreading droppings throughout air vents? Investigators are testing rodents and any droppings found onboard.
• What do patients have in common? Epidemiologists are mapping each case: cabin location, dining arrangements, shore excursions, and daily routines. They’re looking for the thread connecting these seven people and separating them from hundreds of others who are so far okay.
• How is it spreading? Hantavirus is not typically transmitted person-to-person. It is known to spread when people inhale aerosolized particles from infected rodent urine, droppings, or saliva.
• But, importantly, there is one type of hantavirus that can spread from person to person, and guess where it comes from? Argentina (where this boat sailed from).
• Investigators need to confirm how this outbreak is spreading because if person-to-person transmission is occurring, the risk calculus changes quickly.
• What is the pathogen itself? The virus is being genetically sequenced to determine its strain and whether it has mutated.

Answers to these questions will come, but there is a silver lining.

This is unfolding in South African waters. South Africa has very fast data, is home to some of the world’s best epidemiologists, and is a true team player in the world of global health, willing to work with (and alert) other countries.

What this means for you: Risk to Americans is essentially nil right now, and the probability of a pandemic remains very, very low.

But let this be a reminder that diseases don’t see borders.

As the U.S. pulls back from institutions like the World Health Organization, it weakens epidemiologists’ ability to communicate across countries, ultimately undermining our ability to protect Americans.

Question grab bag

My grandpa asked me this, so I suspect it’s on a lot of minds: Do I really need a spring Covid shot?

My answer to him: It’s messy, but I would say yes.

Current CDC guidance recommends two updated doses per year for people over 65:

one in fall, one in spring. A recent CDC study (blocked from publication by political appointees, but valid) found that the winter vaccine continues to provide 55% additional protection against severe disease and death.

Last year, around 40,000 people still died from Covid-19.

That said, robust data comparing one versus two annual doses are genuinely scarce.

What we do know: summer Covid waves have occurred for six straight years, and recent summer waves have been larger than winter ones. If that pattern holds, June or July is when things pick up, making late May the sweet spot for vaccination.

Age matters, too.

Older immune systems have a harder time holding onto immunological memory, which is why the guidance skews toward more frequent boosting for seniors.

The data aren’t perfect, but for older adults, the benefits still outweigh the risks.

Good news

• Infant formula is (confirmed) safe! A new FDA report tested infant formula for heavy metals (arsenic, lead, cadmium, and mercury) and PFAs. Levels were well below European standards, which are the strictest in the world.
• Physician burnout is declining for the third consecutive year, to 41% (down from 48%). Although there is a whole lot more progress to be made, it is important to understand what is driving this trend and keep pushing for structural changes.
• There was a big drop in bird flu detections last week. It’s the turn of the season, and detections are down among backyard chickens, commercial farms, and wild birds. Last week brought only one new report of a poultry facility with H5N1.
• A Danish study showed promising impacts of Wegovy, an obesity drug, on heavy drinking. In the 108-person study, people with alcohol use disorder and obesity reported reduced days of heavy drinking in a month-long period (–41·1 percentage points) than before they started on Wegovy. This is the first controlled trial that looked at impacts of the drug on alcohol consumption. It’s a small study, so there’s more work to be done, but the results are promising.

Bottom line

We may be out of the winter season, but public health never gets boring. Stay healthy out there!

Love, YLE

Your Local Epidemiologist (YLE) is founded and operated by Dr. Katelyn Jetelina, MPH PhD—an epidemiologist, wife. YLE reaches over 425,000 people in over 132 countries with one goal: “Translate” ever-evolving public health science so that people are well-equipped to make evidence-based decisions. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below: