A worker at a fish-processing factory in Ghana's Atlantic seafront city of Tema infected 533 other workers at the facility with the coronavirus, Ghana's President Nana Akufo-Addo has said in a broadcast.
Ghana's health authorities reported the outbreak at the industrial facility late on Friday, but did not provide details.
"All 533 persons were infected by one person," President Akufo-Addo said.
He did not provide details of how the disease spread in the facility or if safety measures had been in place.
He said that the 533 positive cases, which represents around 11.3 percent of Ghana's total infections, were part of a backlog of about 921 cases going back as far as April 26 that are only recently being reported.
The new cases pushed Ghana's total since the pandemic was first reported in the country in mid-March to 4700 as of Sunday night, the highest number of infections in West Africa.
The president said 22 people have died of coronavirus-related causes, while 494 had recovered.
With 160,501 tests since the outbreak, Akufo-Addo said Ghana had carried out more tests per million people than any other country in Africa.
"The implementation of our strategy of aggressively tracing, testing and treating is our surest way of rooting out the virus," Akufo-Addo said.
He announced an extension of a ban on public gatherings until the end of May, and schools and universities will remain closed.
Akufo-Addo eased a three-week lockdown on Ghana's two main cities, Accra and Kumasi, on 19 April amid concerns over a prolonged lockdown on the economy.
Deaths in Africa
As many as 190,000 people across Africa could die in the first year of the coronavirus pandemic if crucial containment measures fail, the World Health Organization (WHO) warns.
New research also predicts a prolonged outbreak over a few years.
"It likely will smoulder in transmission hot spots," says WHO Africa head Matshidiso Moeti.
This patchier and slower pattern of transmission sets Africa apart from other regions, WHO experts say.
Other factors taken into account are the region's younger populations who have "benefitted from the control of communicable diseases such as HIV and tuberculosis", as well as lower mortality rates.
The study finds that between 29 million and 44 million people in the WHO African region could get infected in the first year of the pandemic. Between 83,000 and 190,000 could die in the same period, it warns.
The estimates are based on prediction modelling, and focus on 47 countries in the WHO African region with a combined population of one billion - Egypt, Libya, Tunisia, Morocco, Eritrea, Sudan, Somalia and Djibouti are not included.
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Across the whole of the African continent more than 2,000 coronavirus deaths have been recorded by Africa's Centre for Disease Control. By comparison, 140,000 have died in Western Europe, where the virus took hold several weeks earlier.
Cases have been recorded in every African nation except Lesotho.
South Africa has the highest number of confirmed cases - more than 8,200 and 160 deaths - while Algeria has the most deaths - 483.
"Covd-19 could become a fixture in our lives for the next several years unless a proactive approach is taken by many governments in the region," Dr Moeti says in a WHO statement.
"We need to test, trace, isolate and treat."
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