Avian Influenza in Egyptian Slum Settlements- The Epidemiology February 9, 2009Posted by Nora in Environmental Health, Global Health.
Tags: avian influenza, developing countries, infectious disease
The influenza pandemic of 1918 was one of the greatest causes of mortality of its time. It resulted in the deaths of up to 50 million individuals worldwide. According to Dr. Trampuz, the avian influenza ( H5N1) virus has fulfilled two of the three criteria that lead to the pandemic of 1918; the current strain of avian influenza has the capability to infect humans and result in high mortality, and the human population is, as a whole, immunologically naïve . The final criterion, human to human transmission of this virus has not been fulfilled. Achievement of this criterion would require mutation of the avian influenza virus genome. Since viruses mutate often and easily it is reasonable to extrapolate the H5N1 realization of the third criterion . As you probably know, Egypt as a country has been tackling cases of avian influenza as of March 2006. According to the most recent World Health Organization (WHO) statistics, nineteen out of a total of fourty-threeindividuals who contracted avian influenza died as a result. I think that the squatter settlements or the Ashwaiayat in Cairo, are particularly relevant when trying to demonstrate Cairo’s unique vulnerability to avian influenza. For the purposes of this blog, I will use “Manshiet Nasser” to represent the slums of Cairo, as they are all relatively similar.
As of April 2007, “Manshiet Nasser” is, as are most settlements, lacking in the basic provisions of urban life. This includes water supply, sewage systems and electricity. Often, families of seven to ten members live in one room. Houses with more than one floor entail several families occupying each floor. In between the alleys a large ditch serves as the public latrine as well as the area for waste disposal. Animals are bred inside the houses, or outside depending on the financial capabilities of that particular family. The settlers purchase containers of water used to cook, clean, and bathe. The inhabitants of this settlement are primarily concerned with providing a source of income for their families, and the practice of child labor is extensive.
According to the WHO, influenza viruses are spread by the inhalation of infectious droplets and skin contact followed by transfer to the upper respiratory tract . Due to these individuals close living quarters an infected individual will quickly transfer the infection to the members of his/her family through skin contact and airborne droplet inhalation. Thus, in the event that Avian influenza becomes transmissible from human to human, this community will become a reservoir for avian influenza. Morbidity data from the Egyptian Department of Health Services as of 2000 shows 9.5% of all Egyptian children suffering from Acute Respiratory Infection. In comparison, studies performed by USAID in “Manshiet Nasser” from the 1980’s through the mid- 1990’s showed 69% of children having some sort of infectious disease and 49% afflicted with a respiratory illness. This drastic difference between slum dwelling and non-slum dwelling children cannot be attributed in its entirety to close living quarters, but it is certainly a factor in the increased transmission of infection and respiratory illness.
This same logic may be, in turn extended to avian influenza; as a successful (or mutated, and thus, pandemic inducing) avian influenza virus will have the capability to bind to receptors on the respiratory tract in a more cohesive fashion than it already does. In the event of a pandemic, the inhabitants of this settlement will contract avian influenza rapidly as the conditions for transmission will be favorable.
In the event of a H5N1 mutation, these settlements will very likely become a reservoir for avian influenza. As of today, a viable genetic mutation causing influenza transmissible from human to human has not occurred. It is pertinent, then to discuss the current strain of Avian influenza, and the environmental determinants of its transmission. Avian influenza may be transmitted from poultry to human through several environmental pathways. According to the WHO, infected poultry has been found to shed the virus in their fecal matter, saliva and nasal secretions. The main force behind the secondary spread of this virus is not animals, as expected, but humans.According to Dr. Capua, and Dr. Alexander,
“Strong evidence has implicated the movements of caretakers, farm owners and staff, trucks and drivers moving birds or delivering food in the spread of the virus both onto and through a farm”.
Avian influenza has been demonstrated to persist in water for periods ranging from 1.5 to 17 days . According to the WHO, it has also been shown to survive in feces for at least four days at room temperature; and with increased preservation of infectivity as temperatures decrease. Consequently shared water or food may become contaminated by mechanical transfer of contaminated feces.
The inhabitants of this settlement often breed poultry as their only or possibly as an additional source of income. Unfortunately, according to Dr. Meliegy, the avian influenza virus was characterized as being deeply entrenched within the Egyptian poultry population as of February 2006 . Given the modes of transmission indicated above, the limited water supply is very relevant to the transmission of this virus. Limited water supply and accordingly limited hygienic practices will only serve to increase the spread of the virus. This is evidenced by the rate of diarrheal diseases, as diarrheal diseases are often spread by fecal-oral contamination of the water and food supply.
The rate of this contamination form is much higher in this community with diarrheal diseases in children at 42% as compared to the Egyptian Department of Health Statistics indications of a 7% prevalence rate of diarrheal diseases in Egyptian children. Not only does avian influenza have a high mortality rate; it is also undesirable for humans to continue to become infected with the influenza virus through birds due to the possibility of the mutation of the virus into one capable of causing infection of pandemic proportions. This mutation may arise in two scenarios; the first is the simultaneous infection of a human with H5N1 and the human influenza virus resulting in genetic re assortment. This situation is exceedingly likely given the high rates of respiratory infection present in this community. The second scenario involves an antigenic shift and the Darwinian principles of natural selection.
Please look out for part two of this post, “Avian Influenza in Egyptian Slum Settlements- An Action Plan”.