Increased demand due to the severe flu season has led to spot shortages of flu medications, but other problems in the supply chain are not far behind.

Hospitals and pharmacies across the United States have reported spot shortages of flu vaccines, medications, and test kits during the peak of flu season.

Some pharmacies that have run out of the flu vaccine don’t plan on restocking their shelves, even as the Centers for Disease Control and Prevention (CDC) has continued to urge Americans to get the flu shot.

Physician practices that have run low on the rapid flu test kit are foregoing the test altogether, or reserving it for patients with milder symptoms.

Demand for the antiviral medication Tamiflu has outstripped local supply in many places around the country. One pharmacy changed up the capsule form so children could take it.

Hospitals also face a shortage of smaller IV bags used to administer fluids to people admitted to the hospital for flu and other conditions.

And the American Red Cross has reported shortages of blood supplies as donations have suffered due to flu and cold weather.

The American Society of Health-System Pharmacists’ Drug Shortages center reported that only the powdered form of two generic versions of Tamiflu were in short supply due to increased demand. Oral capsules of Tamiflu and generics were unaffected.

Spot shortages are driven in part by the severity of this year’s flu season, which is on track to becoming one of the worst in recent years.

According to the CDC, hospitalizations due to the flu had risen to 60 per every 100,000 people as of Feb. 9.

One doctor who listened in on a CDC briefing earlier this month told WBRC in Alabama that spot shortages are more a problem of getting the drugs and test kits to where they’re needed, rather than a supply issue.

When many people seek out vaccination or treatment for flu-like symptoms over a short time, local supplies may run out before they can be replenished.

Pharmacies may also be hesitant to stock too many vaccine shots — or restock when they run out — because unused supplies will expire in June and need to be discarded. This can lead to less-than-complete vaccine coverage for an area.

The flu kit shortage, though, was worsened when the U.S. Food and Drug Administration (FDA) removed two brands — Osom and QuickVue — from the market because they were “performing poorly, resulting in many misdiagnosed cases.”

Even before flu season hit, some health professionals had been raising the alarm about the country’s lack of preparedness and its shaky medical supply chain.

In October, Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, told Newsweek that about 30 essential medical items made outside the United States are at risk of shortage. This includes drugs and IV bags.

A major flu outbreak in the countries where these products are made could keep people from getting to work and interrupt the manufacture of those products.

But it’s not just pandemics that can impact the country’s medical supplies.

Healthcare company Baxter International said that it lost “multiple production days” at its manufacturing facility in Puerto Rico after Hurricane Maria in September.

This led to a shortage of smaller-volume IV bags, which are made at that facility. The shortage worsened when hospital demand for these bags increased during the flu season.

Modern Healthcare reports that only one other manufacturer supplies the United States with these smaller-volume IV bags. That company wasn’t able to offset the supply lost after the hurricane.

In an effort to ease these shortages, federal regulators gave Baxter approval to import large saline bags from its facility in Mexico.

Shortages aren’t unique to IV bags, though.

A report by the U.S. Government Accountability Office found that there were 427 drug shortages in the country in 2015. More than half had been ongoing since at least the previous year.

Demand for these drugs is often ongoing, unlike flu vaccines that are good only for one season.

The dominant influenza virus strains change from one flu season to the next. Some strains may even change their genetic makeup rapidly during the year.

Each year’s flu vaccine is the FDA’s best guess of which strains will occur during the upcoming season. But this sometimes misses the mark. Initial reports have stated that this year’s vaccine was only 36 percent effective.

Which is why Sen. Edward Markey (D-Mass.) and other senators called last week for a $1 billion investment in finding a universal flu vaccine that would allow a lifetime of protection with only one or two shots.

A universal vaccine would enable people to get vaccinated any time during the year. This would reduce the surges in demand that currently occur around this time.

But it won’t solve the other problems that make it hard to get enough medications to where they need to go in the country.

And it definitely won’t prevent natural disasters like Hurricane Maria from striking facilities where drugs and medical supplies are made.

Still, it’s one less thing to worry about at the start of flu season.