The coronavirus has now been confirmed in at least 30 of Africa's 54 countries, officials said, as regional power South Africa warned of a new crisis once the virus begins to spread at home and into crowded low-income communities.

The most alarming confirmation of a first case came from Somalia, the Horn of Africa nation with one of the continent's weakest health systems after nearly three decades of conflict. Tanzania, Liberia and Benin also announced their first cases on Monday.

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African nations have begun imposing travel restrictions as many confirmed cases came from abroad. Algeria cut off all air and sea contact with Europe, effective Thursday.

South Africa announced it will revoke nearly 10,000 visas issued to people from China and Iran, two of the hardest-hit countries, in January and February. It also will require visas from several hard-hit countries that had been visa-free, including the United States and Italy.

Both are dramatic steps that target important business partners at a time when South Africa's economy has again slid into recession.

“The internal transmission risk is now setting in,” South Africa's health minister, Zweli Mkhize, told reporters a day after the country declared an unprecedented national disaster. It has 62 cases, all from abroad. Health officials are investigating two cases of possible local transmission.

"The reality is this: For now, individuals that have been infected thus far are people who can afford going on holiday abroad or they travel for business. Those individuals also have accommodation for self-quarantine," the minister said.

"However, when this outbreak starts affecting our poor communities where families do not have enough rooms or spaces to quarantine those affected, we will experience a crisis."

South Africa might have to impose a "lockdown" if these and other new measures including travel restrictions and school closures don’t work within two weeks, the health minister said: "It's going to be very hard."

Weak health systems

South Africa has one of the most developed health systems in Africa, and global health experts have openly worried for weeks that the virus could quickly overwhelm countries on the continent with weak health systems.

Somalia is one of them. Health Minister Fawziya Abikar said the country's first confirmed case was in a Somali national who had recently arrived from abroad. Somalia's government quickly announced that international flights to the country would no longer be allowed as of Wednesday.

Large parts of Somalia remain under the control of the al-Qaeda-linked al-Shabab armed group, which has been hostile to aid groups and often carries out deadly attacks in the capital, Mogadishu. The insecurity will hurt efforts to contain the virus.

In Liberia, the executive director of the country's environmental protection agency tested positive after arriving last week from Switzerland.

Liberia, along with neighbours Sierra Leone and Guinea, was devastated by an Ebola outbreak from 2014 to 2016 that killed more than 11,300 people.

"There is no cause for panic," Information Minister Eugene Lenn Nagbe said.

Tanzania's health ministry said the country's first confirmed case was a 46-year-old Tanzanian woman who recently traveled from Belgium. Tanzania came under unusual criticism from some global health officials last year after the East African nation was accused of not sharing information about a possible Ebola virus case.

Tough measures

Medical staff of the Ethiopian health ministry prepare to screen passengers at Addis Ababa Bole International Airport [File: Luke Dray/Getty Images]

In light of the situation, several African nations have implemented drastic measures in the hope of slowing down the spread of the coronavirus.

In East Africa, Indian Ocean holiday paradise Seychelles closed schools for at least two weeks in Mahe, the largest of the archipelago's islands, after three confirmed cases of the coronavirus on its shores, the health ministry said.

Ethiopian Prime Minister Abiy Ahmed announced on his Twitter account on Monday that schools, sport events and large gatherings would be suspended in the East African country for 15 days.

In West Africa, Ghana closed all schools and universities and banned public gatherings, including services in mosques and churches, after it confirmed its sixth coronavirus case.

Ghana and Liberia also imposed a temporary ban on noncitizens travelling from countries that have recorded 200 or more cases of the pandemic.

Cameroon confirmed two additional cases of the virus, bringing the total number of infected people to five.

Concern over rising numbers

For most people, the coronavirus causes only mild or moderate symptoms, such as fever and cough. But severe illness can occur, especially in the elderly and people with existing health problems.

Worldwide, over 169,000 people have been infected and 6,500 have died while nearly 77,000 have recovered, most of them in China.

Across Africa, health experts worried that other virus cases were going undetected.

"We have to ask the question: How strong are our monitoring systems, especially those in rural areas or with limited technology? That is a reality on the continent and perhaps why we have not yet seen a surge in cases," public health researcher Shakira Choonara told The Associated Press.

Professor Cheryl Cohen with South Africa's National Institute for Communicable Diseases expressed concern that the current numbers could rise rapidly.

"The major area for the virus is now Europe, and we are connected more to Europe and US than we are with China," she said.