Africa will likely see higher numbers of coronavirus cases in coming weeks because of the likelihood some are slipping through the net, the head of a regional disease control body said on Thursday.

The virus has multiplied in Africa more slowly than Asia or Europe, but 34 nations on the continent have now reported a total of more than 600 cases. Worldwide, it has infected nearly 220,00 people and killed nearly 9 000.

“We are picking some people but we are also missing some people,” said John Nkengasong, head of the Africa Centres for Disease Control and Prevention (CDC) which is a branch of the African Union bloc.

“The situation will get worse before it gets better because the chances are clear that people have slipped through.”

Many countries worldwide have suspended flights, closed borders and banned public gatherings to curb its spread.

Nkengasong said the number of confirmed cases in Africa was expected to rise in coming days and such travel bans would delay but ultimately fail to contain the virus.

“Anyone who has followed pandemics over the years, you know that doesn’t work,” he told a news conference in the Ethiopian capital. “When you lock down countries, you should understand clearly how to unlock the country.”

It was very likely, he said, that “people are coming in and they are slipping through and we are not picking them.”

Nkengasong said testing was going to increase as more kits became available. U.S. company Abbott, Swiss-based Roche Diagnostics and California-based Cepheid’s GeneXpert were all ramping up production, he said. The testing could be rolled out quickly through existing HIV infrastructure, he said.

Matshidiso Moeti, the World Health Organisation’s (WHO) Africa head, was less concerned than the CDC head about missing cases.

“We actually don’t believe that there are large numbers of African people who are undetected and infected,” she said on a teleconference with the media.

Moeti said 40 African countries can now test for the virus, up from just South Africa and Senegal at the start of February.

WHO Africa is planning to help countries set up pop-up hospitals that could be equipped with ventilators and oxygen, she added.

Moeti said countries should isolate suspected and confirmed cases but without cutting off other nations.

In Kenya, which has seven confirmed cases, the government will start doing random screenings for coronavirus, Health Minister Mutahi Kagwe said.