Influenza Pandemic Risk Assessment and Preparedness in Africa

This report states that Influenza pandemics are rare but recurring events that have periodically affected humanity since ancient times. They are invariably associated with a rapid surge, experienced globally, in the number of cases of respiratory illness and death. Three
pandemics occurred during the previous century: in 1918 (Spanish flu), 1957 (Asian flu)
and 1968 (Hong Kong flu). The 1918 pandemic is considered one of the most lethal
infectious disease events in the history of humanity: it killed 40–50 million people within
a year, and took its heaviest toll on young adults in the prime of life. Subsequent
pandemics were much milder, with an estimated two million deaths in 1957 and one
million deaths in 1968. During the past pandemics, the groups most severely affected were
similar to those affected during normal seasonal influenza, i.e. the very young, elderly,
chronically ill and persons with compromised immune systems.

According to the report, for almost two years, health experts at WHO and elsewhere have been monitoring a new and extremely severe influenza virus, the highly pathogenic H5N1 strain. Since mid-2003, this virus has caused the largest and most severe outbreaks of highly pathogenic disease ever recorded in poultry. Some 150 million domestic birds have died or been culled in nine south-east Asian nations. Losses for the agricultural sector have been estimated at US$ 10 billion.

In December 2003, infections in people exposed to sick birds were identified. Since
then, at least 120 human cases have been laboratory confirmed in four Asian countries
(Cambodia, Indonesia, Thailand and Viet Nam); more than half of these people have died.
Unlike normal seasonal influenza, where infection causes only mild respiratory symptoms
in most people, the disease caused by H5N1 follows an unusually aggressive clinical
course, with rapid deterioration and high fatality. Primary viral pneumonia and multiorgan
failure are common. In the present outbreak, most cases have occurred in previously
healthy children and young adults. The species barrier is significant: the virus does not
easily jump from birds to humans. However, a major implication for human health is that
the virus will change into a form that will spread easily from person to person.

The arrival of highly pathogenic H5N1 avian influenza on the African continent
would be of great concern for human as well as animal health. Though the densities of
human and poultry populations are generally lower in Africa than in south-east Asia, the
poultry production systems have many similarities which could create multiple
opportunities for human exposure, if outbreaks occur in African poultry. In Africa, many
households keep backyard flocks which often mingle freely with wild birds. Most such
flocks scavenge for food, often entering households or sharing outdoor areas where
children play.

In Africa, the risk of human infection from an avian H5N1 virus can be expected to
be similar to that seen in Asia. To date, the majority of human cases in Asia have been
linked to close contact with infected domestic birds, with especially high risks thought to
occur during home slaughter, defeathering, butchering and preparation for cooking.
Consumption of inadequately cooked poultry and poultry products (including eggs and
blood) is an additional risk. African households, especially in rural areas, traditionally slaughter and consume birds when signs of illness appear in backyard flocks. As in Asia,
such practices could prove difficult to change.

The occurrence of human cases, even sporadic, would create enormous new
challenges for health systems and services that are already fragile and overburdened. Early
detection of human cases is unlikely. Surveillance systems are weak and unlikely to pick
up cases of a disease with symptoms similar to those of common illnesses. Health service,
human and financial resources have been overwhelmed by the demands of AIDS,
tuberculosis and malaria. Laboratory confirmation of human H5N1 infections requires
technology, finances and trained personnel.