INSIGHT-Puzzled scientists seek reasons behind Africa's low fatality rates from pandemic

* Africa's COVID-19 fatality rates lower than Europe, U.S.
* Experts cite youthful population, strict lockdowns
* Could TB vaccine also offer protection against COVID-19?

By Alexander Winning
JOHANNESBURG, Sept 29 (Reuters) - Africa's overburdened
public health systems, dearth of testing facilities and
overcrowded slums had experts predicting a disaster when
COVID-19 hit the continent in February.
The new coronavirus was already wreaking havoc in wealthy
Asian and European nations, and a United Nations agency said in
April that, even with social-distancing measures, the virus
could kill 300,000 Africans this year.
In May the World Health Organization (WHO) warned that
190,000 people on the continent could die if containment
measures failed. Yet as the world
marks 1 million COVID-19 deaths, Africa is doing much better
than expected, with a lower percentage of deaths than other
continents.
The continent's case fatality count stands at 2.4%, with
roughly 35,000 deaths among the more than 1.4 million people
reported infected with COVID-19, according to Reuters data as at
late Monday. In North America, it is 2.9% and in Europe 4.5%
Hard-hit countries such as Italy and Britain have recorded
fatality counts of 11.6% and 9.0% respectively, compared to 1.6%
for Ethiopia, 1.9% for Nigeria and 2.4% for South Africa, the
continent's worst affected country.
Hospitals in many African countries say COVID-19 admission
rates are falling.
"Based on what we have seen so far it is unlikely that we
are going to see anything at the scale that we are seeing in
Europe - both in terms of infections and mortality," said
Rashida Ferrand, a London School of Hygiene and Tropical
Medicine professor working at the Parirenyatwa Group of
Hospitals in the Zimbabwean capital Harare.
Experts say that some COVID-19 deaths in Africa probably are
being missed. Testing rates in the continent of about 1.3
billion people are among the lowest in the world, and many
deaths of all types go unrecorded. South Africa saw some 17,000 extra deaths from natural
causes between early May and mid-July, 59% more than would
normally be expected, according to a July report from the South
African Medical Research Council. That suggests the death toll
from COVID-19 could be significantly higher than the official
figure, currently over 16,000, researchers say.
Even so, there is wide agreement that COVID-19 fatality rates
have not so far been as bad as predicted.
Why? Scientists and public health experts cite a number of
possible factors, including the continent's youthful population
and lessons learned from previous disease outbreaks. African
governments also had precious time to prepare due to the
relative isolation of many of their citizens from airports and
other places where they could come into contact with global
travellers.
Some scientists also are exploring the possibility that a
tuberculosis vaccine routinely given to children in many African
countries might be helping reduce deaths from COVID-19.
Another theory being considered is whether prior exposure to
other coronaviruses including those that cause the common cold
has provided a degree of resistance in some of the very
communities once thought to be most vulnerable.
"There is a lot of circumstantial evidence," Salim Abdool
Karim, a South African infectious disease specialist who has
advised the government on COVID-19, told Reuters, "but there is
no smoking gun."

LESSONS LEARNED
The virus hit Africa later than other continents, giving
medical personnel time to set up field hospitals, source oxygen
and ventilators, and learn from improvements in treatment
elsewhere.
"We got the gift of time," said Thumbi Mwangi, senior
research fellow at the University of Nairobi's Institute of
Tropical and Infectious Diseases. "We had an amount of
preparation that others did not."
One reason could be that international travel is limited in
many African countries, and travelling domestically can be more
difficult than on other continents, Matshidiso Moeti, WHO
regional director for Africa, told a news conference on
Thursday.
The continent's governments have also battled deadly
infectious diseases such as Ebola, which killed more than 11,000
people in West Africa in 2013-16. So officials took notice when
the new coronavirus started spreading around the globe rapidly
early this year. Many African countries were quick to introduce screening at
airports, suspend flights from heavily affected nations and
enforce social distancing measures and mask wearing.
Within a week of Kenya reporting its first case, schools
were shut, incoming travellers had to undergo a mandatory
quarantine and large gatherings were banned. Nigeria, Africa's
most populous nation, imposed a ban on interstate travel and a
curfew. Many of its land borders had already been closed since
August 2019 to cut down on smuggling, which helped fight the
pandemic too.
South Africa introduced one of the world's toughest
lockdowns in late March, when the country had confirmed just 400
cases. "Africa brought down the hammer earlier in terms of
coronavirus lockdowns," said Tim Bromfield, regional director
for East and Southern Africa at the Tony Blair Institute for
Global Change, a U.K.-based think tank.
Experts also point to the continent's demographics.
Research has found that the risk of developing severe
COVID-19 increases with age.
A 2019 United Nations report said 62% of sub-Saharan
Africa's population was under 25 and just 3% 65 or over. In the
U.N.'s Europe and North America region, 28% were under 25 while
18% were age 65 and up.
Chikwe Ihekweazu, director general of the Nigeria Centre for
Disease Control, attributed his country's relatively low case
mortality rate in part to the fact that the majority of patients
were between the ages of 31 and 40.

CROSS-PROTECTION?
Scientists in several countries including South Africa are
testing whether the century-old Bacille Calmette-Guérin (BCG)
vaccine, widely used on the continent against tuberculosis,
provides a degree of cross-protection.
BCG vaccines have been shown to protect against other viral
respiratory illnesses, and a study published in the scientific
journal Proceedings of the National Academy of Sciences in July
found that countries with higher vaccination rates for
tuberculosis had lower peak mortality rates from COVID-19.
Studies have also started in South Africa and Zimbabwe to
assess the impact of past exposure to other coronaviruses.
More than half of Africa's urban population is concentrated
in slums, where access to water for hand washing is scarce, and
physical distancing is near-impossible.
Diseases spread rapidly under such conditions, but some
scientists wonder whether that may have been an unexpected boon
in this case. There is some evidence that T cells developed by
the body's immune system after exposure to other common cold
coronaviruses could help fight off COVID-19. "I would say that is at least a plausible explanation as to
why there are different levels of resistance to the virus in
different populations," said Thomas Scriba, an immunologist and
deputy director of the South African Tuberculosis Vaccine
Initiative.
Others are more sceptical.
"All other regions have been exposed to coronaviruses, have
poor people and slums and have received BCG vaccination," said
Humphrey Karamagi, team leader for data and analytics at the
WHO's Africa office. "We are most probably looking at a mix of
multiple factors working together - and not a single magic
bullet."
For Sam Agatre Okuonzi, from the Arua Regional Referral
Hospital in Uganda, the doomsday predictions were informed by
entrenched prejudices, including that the continent is prone to
disease.
"COVID-19 has shattered a lot of biases about disease in
general but also about Africa," he told Thursday's briefing.
"The severity of the pandemic has not played out in line with
the outrageous predictions."