The relatively low number of coronavirus cases in Africa so far "have raised hopes that African countries may be spared the worst of the pandemic", in the words of the UN. But at the same time it urges caution.

There is a general consensus among those in charge of health policy on the continent that testing rates are woefully low, and this could be distorting our understanding of how far the virus has spread.

As countries move beyond the lockdown phase-only testing and surveillance will allow governments to really know what is going on.

Of course, there are wide variations in testing policy across the more than 50 countries but cases could be going undetected, epidemiologists say.

The early apparent successes in combatting the spread of the virus were notable, and the number of cases has not risen as quickly as elsewhere.

Many countries acted swiftly where, to varying degrees, lockdowns, partial lockdowns, bans on large gatherings, curfews and border closures were introduced.

South Africa, Cameroon, Mauritania and parts of Nigeria launched massive community door-to-door campaigns to screen people and identify potential cases for testing.

Some island nations and countries with smaller populations on the continental mainland have kept the numbers low.

Seychelles last reported a case in early April and the 11 confirmed coronavirus cases have all recovered. Namibia had not had a case for more than a month until two women who were in quarantine, after arriving from neighboring South Africa, tested positive on 21 May.

In Mauritius two people who had been repatriated from India and placed in quarantine tested positive on Sunday - the first new cases for more than a month.

The South African authorities imposed a very strict lockdown which appeared, in its initial phase, to slow the spread of the virus. But President Cyril Ramaphosa, while announcing an easing of the lockdown, said the country should expect infection numbers to "rise even further and even faster".

"The coronavirus pandemic in South Africa is going to get much worse before it gets better," he added.

Nonetheless, South Africa may be in a better position than many other countries on the continent as it is now administering around 10 tests per 1,000 people every day. The country's testing capacity is also growing.

Huge discrepancies

But continent-wide there is a mixed picture.

The director of the Africa Centres for Disease Control and Prevention (Africa CDC), Dr John Nkengasong, said that in mid-May, only 1.3 million tests had been conducted across the continent.

That translates to a continental average of one test per 1,000 people. There are however huge discrepancies between countries.

Smaller and wealthier nations, like Mauritius, have some of the highest rates, even by global standards.

On 12 May, the government there said it had carried out more than 73,500 tests, which is the equivalent of 61 tests for every 1,000 people - a higher figure than either Germany or the UK at that point.

Less affluent countries and those experiencing ongoing internal conflict have tested the least.

According to figures compiled by the International Rescue Committee, Chad has done 0.1 tests per 1,000 people and Mali 0.17 per 1,000.

But Nigeria, the continent's most-populous country - and one of the richest, has carried out 0.23 tests per 1,000.

In response to this low figure, the Nigerian government says it is focused on clusters of outbreaks rather than mass testing of the population.

Chikwe Ihekweazu, director-general for the Nigeria Centre for Disease Control, said in late April: "I would rather go a little bit slower and get it right than speed into a situation that we will end up regretting."

There are also big gaps in the data, such as in Tanzania, which stopped testing. President John Magufuli declared a thanksgiving period to celebrate a decline in the number of people with coronavirus - despite significant numbers of positive cases continuing to be detected along its borders with Kenya and Zambia.

Neighbours have announced border closures fearing an upsurge in imported cases.