Doctors in Nigeria have gone on strike, demanding face masks and pay that reflects the rising risk.

Hospital staffers in Guinea-Bissau had to shutter a treatment ward after nearly everyone on the floor got sick.

Nurses in Cameroon are working through fevers — even dodging tests — because they can’t afford to lose a shift’s wages.

The coronavirus pandemic has tightened its grip on much of Africa, where reported cases have more than tripled over the last month, jeopardizing overstretched medical teams as the need for care soars.

From the pandemic’s early days, leaders across the continent urged prevention and took aggressive action — sealing borders, tracing contacts and building extra isolation wards — asserting that many places lacked the resources to withstand unchecked outbreaks.

Now African health officials and medical professionals are raising concerns about cracks in a crucial armor: Infections among health-care workers have shot up 203 percent since late May, according to the World Health Organization’s Africa arm, following a spike in community transmission and a drop in access to protective gear.

The trends have alarmed epidemiologists at the Africa Centers for Disease Control and Prevention, who warned in a June report that most countries face a “catastrophic shortage” of medical professionals.

While the novel coronavirus has infected devastatingly high shares of health-care workers worldwide, African nations, on average, have far fewer staffers who can fill in on the front lines. The sub-Saharan region has 0.2 doctors for every 1,000 people, according to World Bank data — well below the world average of 1.6. (North America has 2.6, and the European Union has 3.7.)

“We cannot stand by and watch our colleagues all get infected,” said Ndukwe Emmanuel Ifeanyi, a national committee member of the Nigerian Association of Resident Doctors, which represents 40 percent of the country’s physicians. “We don’t have enough manpower.”

Travel and export restrictions have cut off a key flow of medical supplies, health officials said, further exposing doctors and nurses.

“We will lose more of an already very, very finite resource,” said Noreen Hynes, director of the Geographic Medicine Center of the Division of Infectious Diseases at Johns Hopkins University.

Tedros Adhanom Ghebreyesus, the WHO director-general from Ethiopia, stressed in March that massive outbreaks could quickly overwhelm hospitals, which are short-staffed across the continent.

Africa carries a disproportionately small fraction of the world’s caseload, though testing remains limited in some areas. But with infections on the rise, health leaders say medical staffs are up against growing obstacles to fend off worst-case scenarios — particularly in West Africa. Funds are often tight.

Liberia is rationing masks and gloves from the 2014-2016 Ebola crisis. The country had recorded more than 650 coronavirus cases by Tuesday — at least 45 of which were health-care workers.

“We’re maximizing the very little resources we have,” said Sia Wata Camanor, chief medical officer at the John F. Kennedy Medical Center in the capital, Monrovia.

She advises staffers to take regular breaks, avoid unnecessary risks and stay home if they start feeling off.

“A positive health worker is very dangerous,” she said. “You expose your colleagues and you expose patients.”

The virus, she tells employees, could stick around like malaria. They must stay healthy and motivated. Recruits are scarce.

Eghosa Owie, a 26-year-old general practitioner in Lagos, Nigeria — Africa’s most populous city — is eyeing the exit.

“There are hardly any medical graduates I know who have not considered leaving the country,” he said, speaking from his quarantine room at a converted hotel. “It’s another epidemic in Nigeria.”

Owie caught a mild case of the coronavirus about two weeks ago. But his workplace conditions bothered him more than his sore throat: He had to make one N95 mask last for two weeks when it was likely only safe for one shift.

How could he help people if he couldn’t protect himself?

Morale is dragging, he said. Some doctors went on strike earlier this month, angry about having to buy their own face masks, among other grievances.

The number of health-care workers in Nigeria who have tested positive (987) has more than doubled from May 19 to June 23, WHO data shows. Some have ended up on ventilators. Ten have died.

Owie, who grew up speaking Nigerian pidgin, passed the time in isolation studying for an English test to work in the United Kingdom.

“All of my classmates, they’ve already taken and passed the test,” he said. “I don’t think — from what I’ve been seeing — that I want to stay here and work in these conditions.”

A couple rooms over in the makeshift quarantine center, another doctor clicked through a digital copy of “The 7 Habits of Highly Effective People.”

Odumade Afolabi, 32, thought he’d quit his job at a private hospital in time to avoid this hassle.

As a doctor who worked eight-hour pandemic days, he still needed to sell perfume on the side to cover his bills. The $500 monthly salary didn’t go far.

So, when an HIV prevention nonprofit offered to pay him three times more, he agreed to start after one last week of shifts. That’s when he started coughing.

“I wanted a safer job. An office job,” he said from his isolation bed. “The risk as a doctor is surreal. The pay doesn’t show that.”

In Guinea-Bissau, an outbreak among health-care workers last month caused the top hospital’s intensive care section to close for a week of deep cleaning.

Practically all the doctors and nurses went into quarantine, said Monica Negrete, head of the country’s Doctors Without Borders mission.

“If someone broke their leg or had a heart attack,” she said, “we had nowhere to take them.”

The episode seemed like a warning, Negrete said. Cases are steadily rising, and less than 2,000 workers are trained to treat patients in a nation of nearly 2 million.

Far fewer can handle serious cases.

In central Cameroon, 293 health-care workers have tested positive for the coronavirus, but experts say the true number is probably much higher.

“We lack tests to test the staff,” said Charlot Essiane, a medical union leader in the capital, Yaoundé.

Some members notice symptoms and opt to self-isolate. One young nurse tapped out after a CT scan found lesions in her lungs.

Patients have to wait longer and longer.

“People who arrive at 7 a.m. aren’t seen by medical staff until 10 a.m.,” Essiane said. “Sometimes noon.”

Tracy, a nurse in the city who spoke on the condition that only her nickname be used out of fear of retaliation, said staffers at her hospital clock in even when they’re feeling sick — they’d rather not miss a day of wages.

A few avoid the tests, she said. She took one in late May after she developed a fever at her fiance’s urging.

The result: positive. She was forced to wait four days to receive medication for the pain.

“They said the hospital had run out,” Tracy said. “I was fighting alone.”

She tried to reach one of her friends — a physician fresh out of school. He’d gotten sick right before she went into quarantine.

“The head of doctors told me, ‘The guy is gone,’ ” she said. She’s still not sure whether that means he left or died.

Borso Tall in Dakar, Senegal, and Oris Aigbokhaevbolo in Lagos, Nigeria, contributed to this report.