2.7 m Kenyans may be exposed to Covid-19, study shows

Scientists and doctors now say Kenya could be in the eye of a Covid-19 storm, estimating that the number of people exposed to the virus is 2.7 million.

Blood samples from several places across the country show there could be a huge gap between confirmed cases and the number of people exposed to the coronavirus.

The data contained in a study by the Kenya Medical Research Institute (Kemri) and Wellcome Trust suggests that many more Kenyans have already been exposed to respiratory diseases than have been identified by surveillance activities.

It found that as many as 12.4 per cent of Nairobi residents could be having the virus. With a population of about 4.5 million, it means slightly more than 550,000 city dwellers could be infected.

According to the study, the prevalence of antibodies to SARS-CoV-2 among blood donors ranged from 1.1 per cent in Uasin Gishu to 12.4 per cent in Nairobi.

Some 500,000 people in the Rift Valley and 400,000 in western Kenya could have been exposed to the virus, it adds. 

There is no data from the northern parts of the country. In Kisumu, the third largest town in Kenya, some 7.5 per cent of the samples tested positive.

It means as many as 90,000 people could have been exposed to coronavirus. The researchers relied on 2,535 blood samples donated between April 30 and June 16. They say Kenya should expect “severe disease…though this has not yet happened”.

“There is a large gap between the confirmed cases identified by rapid response teams in testing and tracing, and the numbers of individuals in the population that we believe have been exposed based on antibody data,” notes the study.

It is now thought that people have had the deadly Covid-19 disease for a long time as governments around the world are testing citizens for coronavirus antibodies, to work out this theory.

The report does not say why this is the case though the country has reported a rising number of Covid-19 asymptomatic cases, leading to the government announcing a home-based care model “in order to stop the health system from being overwhelmed by the pandemic”.

ASYMPTOMATIC

It is estimated that 78 per cent of patients are asymptomatic or have mild symptoms. Just days ago, Health Chief Administrative Secretary Rashid Aman said the country has entered the Covid-19 peak season, starting from July through to September.

That means Kenya should brace itself for more coronavirus cases, he added. The country had had 6,951 confirmed cases after testing 173,355 samples by Thursday.

Nairobi still leads with 3,526 cases.  It is followed by Mombasa with 1,548. In Mombasa, where chances of getting infected are the highest in the country, the study estimates that 100,000 people – or 8.6 per cent of the coastal city's population – have been exposed to Covid-19. Interestingly, there is no data from the northern parts of the country.

“There is a large gap between the confirmed cases identified by rapid response teams in testing and tracing and the number of individuals in the population that we believe has been exposed, based on antibody data,” the study says.

Globally, the cases have hit 11 million and more than 550,000 deaths.  The number of deaths in Kenya has reached 149.

While the first Kenyan case was confirmed on March 4 and announced on March 13 by Health Cabinet Secretary Mutahi Kagwe, there are high chances that many people may have been infected and survived without realising it.

If the pattern holds, the results from the study on antibody prevalence from blood donor samples in the country raise the tantalizing prospect that many Kenyans who never knew they had been infected had already encountered the virus, and survived.

The Kemri team tested donated blood for proteins made by the body to attack foreign substances such as viruses and bacteria scientifically known as antibodies.

The presence of these antibodies in blood indicates the individual has ever been infected — even if that person never showed symptoms.

While the team of scientists said that the large numbers of the population that have been exposed would lead models to predict significant numbers of severe cases and deaths, county hospitals in which monitoring for pneumonia admissions is established are not seeing high numbers of admissions.

County hospitals where monitoring of pneumonia admissions is well established have not recorded high Covid-19 numbers.

REOPENING ECONOMY

It means people are not getting severely sick or are asymptomatic, the study goes on. It is the asymptomatic carriers that are a cause of worry for the government.

Information from the National Registry of Diseases shows that there was an increase of pneumonia cases from the time Kenya reported its first coronavirus case.

Pneumonia is one of the complications of severe Covid-19.  Between January and early February, the number of pneumonia cases was 137,667. It then shot up dramatically to 195,504.

The pattern – an increase from January and then a plateau – is not similar for the same period in 2019.

While this latest study is important because blood donors are a convenient sample of the community, it acknowledges that “we may not be representatively sampling the country’s population”.

The researchers say accurate antibody testing is critical in helping determine when and how to begin restarting the economy and sending Kenyans back to work.

“Testing a sample of the population for antibodies tells us how many people have been exposed to the virus,” it says.

Random testing of 2,535 blood samples testing suggests many more Kenyans have already been exposed to Covid-19 than have been identified by surveillance activities.

Antibodies are thought to stay positive for several months and can be a gateway to determining whether a person has been infected before can be detected by testing the blood.

Normal PCR tests on throat and nose swabs only reveal active infection and cannot reveal people who have recovered from infection.

“Testing a sample of the population for antibodies tells us how many people have already been exposed to the virus at some time in the past,” reads the study.

The Kemri study, however, may not be representative of the general population as the sample sizes were too small for the results to be extrapolated to the wider population. For instance, in Nairobi only 137 blood samples were tested for antibodies.

“The ideal way of estimating exposure to Covid-19 in the Kenyan population would be visiting randomly selected homesteads to collect and then test blood samples.  This has not been practical under current restrictions,” the researchers noted.

Scientists believe that accurate antibody testing is seen as a critical tool to help determine when and how to begin restarting the economy, and sending people back to work.

DEADLY VIRUS

President Uhuru Kenyatta last week said reopening the economy would depend on measures put in place to stop the spread of the deadly virus and the level of preparedness by devolved governments.

Mr Kenyatta said the decision to reopen the economy would be determined by the county government’s capacity to respond to new cases of Covid-19 effectively.

The findings come at a time new global studies suggest that people testing negative for Covid-19 may still have some immunity.

Researchers at Karolinksa Institute, Sweden, found that for every person testing positive, two were found to have T-cells which identify and destroy infected cells. This was seen even in people who had mild or symptomless cases of Covid-19.

But it's not yet clear whether this just protects that individual, or if it might also stop them from passing on the infection to others.

The team of researchers tested 200 people for both antibodies and T-cells. Some were blood donors while others were tracked down from the group of people first infected in Sweden, mainly returning from earlier affected areas like northern Italy.

This could mean a wider group have some level of immunity to Covid-19 than antibody testing figures, like those published as part of the UK Office for National Statistics Infection Survey, suggest.

It's likely those people did mount an antibody response, but either it had faded or was not detectable by the current tests.