In March and April 2009, an outbreak of H1N1 influenza A virus infection was detected in Mexico, with subsequent cases in many other countries. On 11 June 2009, WHO raised its pandemic alert level to the highest level (phase 6), indicating widespread community transmission in at least two continents. The influenza virus can be transmitted through sneezing and coughing through large-particle aerosols, as well as by contact with surfaces that have been contaminated with respiratory droplets 1.
Although the incubation period has not been established for pandemic H1N1 influenza A infection, it could range from 1 to 7 days, and most likely from 1 to 4 days 2.
Immunocompetent patients with pandemic H1N1 influenza A virus infection are likely to be contagious from 1 day before the development of signs and symptoms until resolution of fever. Longer periods of shedding may occur in children (especially young infants), the elderly, patients with chronic illnesses, and immunocompromised hosts 3.
The aim of this work
This was an epidemiological study of children with pandemic influenza A (H1N1) in one medical center (Egypt).
Patients and methods
In this retrospective case series study, we reviewed the files of 95 children admitted at Imbaba fever hospital, Giza (Egypt), with pandemic H1N1 influenza, confirmed by a reverse transcription-PCR from June 2009 to May 2010. There were 63 males and 32 females, mean age 9.6±4.74 years.
We extracted the following data from their hospital charts: age, sex, residence, clinical features at presentation, course, duration of the illness, treatment used and their outcome. Also, investigations were performed for history of medical conditions that may be risk factors for influenza-related complications.
All patients were admitted because of the presence of at least three of the clinical symptoms of fever, rhinitis, cough, and gastro-intestinal tract symptoms at the time of the pandemic; the diagnosis of influenza A (H1N1) was confirmed by laboratory tests:
- A complete blood count.
- C-reactive protein.
Nasopharyngeal swab specimens with a synthetic tip (polyester) and plastic shaft were obtained as soon as possible following the onset of symptoms. The collection vial in which the swab was placed contained 1–3 ml of viral transport media and was placed on ice (4°C) or refrigerated immediately for transportation to the central labs of the ministry of health. Then, PCR – nucleic acid amplification tests, using primers, were carried out.
The collected data were tabulated and analyzed using the SPSS program (SPSS Inc., Chicago, Illinois, USA); the Z-test was used to compare between 2 percentages of two groups.
Over a period of about 12 months, 95 children were admitted to Imbaba fever hospital; they were laboratory-confirmed cases of pandemic H1N1 influenza.
Figure 1 shows that the percentage of male patients was higher than female patients (66.7 and 33.3%, respectively). The age range study group was 1–18 years, mean 9.6±4.74 years.
We found that the percentage of affected children living in suburban areas was 49.5%, that in rural areas was 30.5% and that in urban areas was 20%, with significant statistical difference between them (P=0.002) (Fig. 2).
According to complete blood count, there was relative lymphocytosis and some cases associated with leukocytosis, mainly in cases of pneumonia.
Table 1 shows that the most common manifestations were fever (100%), sore throat (87.4%), and cough (75.8%).
Fourteen children had radiographic changes compatible with pneumonia [eight cases of bronchopneumonia (8.4%) and six cases of lobar pneumonia (6.3%)] (Fig. 3).
Only 10 children in the study group had previous medical problems (six had bronchial asthma and one case each of diabetes mellitus, epilepsy, congenital heart, and glucose 6 phosphate dehydrogenase).
Figure 4 shows that 81 children were completely cured by the usual dose of oseltamivir and 14 children had complications of pneumonia and bronchopneumonia, and required treatment by an extended dose of oseltamivir; 11 children improved and three had complications and had to be admitted to the ICU, with no recorded mortality.
In our study, the age of the patients ranged from 1 to 18 years, mean 9.6±4.74 years. In our study, the incidence of H1N1 was higher in male patients than female patients (66.7 and 33.3%, respectively).
We found that residence in suburban or rural areas was a risk factor for the development of H1N1 as most of the patients were from these areas. This may be because of overcrowded conditions, poor ventilation, and low health education in suburban areas, and this is in agreement with study carried out by David et al. 4.
The majority of patients with pandemic (H1N1) 2009 infection develop mild upper respiratory tract symptoms; this was similar to that of seasonal influenza but gastrointestinal symptoms were more common in the former. The most common presenting symptoms in our study were fever (100%), sore throat (87.4%), and cough (75.8%). The result of our study is in agreement with that of another study carried out in the USA for 642 confirmed cases in early outbreak for the same age group; it was found that fever, cough, and sore throat were the most common presenting symptoms 5. Another study of 863 confirmed cases in Ontario (Canada) also found that fever, cough, and sore throat were the most significant symptoms 6.
Fourteen children had radiographic changes compatible with pneumonia [eight bronchopneumonia (8.4%) and six lobar pneumonia (6.3%)]. In another study, 66 patients with pandemic H1N1 influenza underwent chest imaging; the most common findings were patchy consolidation involving lower and central lung zones 7.
Only three children were admitted to the ICU. Two of these children had difficulty in breathing and they had risk factors of asthma and one child had encephalitis; she was 5 years old and presented to our hospital with altered conscious level, fever, and signs of influenza-like illness. Cerebrospinal fluid) examination indicated clear aspect with high tension and mainly lymphocytes. In a study carried out on 58 children in Canada, it was found that one patient also had symptoms similar to encephalitis; the patient presented with disturbed conscious level with status epileptics. MRI showed no specific changes in white matter, EEG showed focal slowing, and cerebrospinal fluid showed no abnormalities 6.
In this study, clinical deterioration is characterized by primary viral pneumonia and failure of multiple organs. The duration of hospital admission was 2–7 days, mean 4.71 days; this is in agreement with the study carried out by O'Riordan et al. 6.
All confirmed cases of pandemic (H1N1) in this study received the usual dose of oseltamivir (tamiflu), and the patients with complications were administered extended double doses. The 2009 flu pandemic was caused by a new strain of the H1N1 influenza virus, which usually has a mild disease course and responds well to oseltamivir; the mortality rate was zero in our study groups.
Pandemic H1N1 influenza did not appear to cause more severe disease than seasonal influenza. It affected mainly adolescents and young adults. Asthma was a more significant risk factor for severe disease. Neuraminidase inhibitors should be used as early as possible when reverse transcription-PCR for H1N1 infection is positive. Infection control measures are very important for the prevention of disease.
Conflicts of interest
There are no conflicts of interest.
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