CARTAS AL EDITOR

Pediatric hospitalizations for the novel influenza a H1N1/2009

Gustavo Sánchez-Huerta, MSc,^I Norma Matías-Juan, MC,^I Adela Dominguez-Basurto, MC,^II Manuel Pacheco-Ruelas, MC, Rodolfo Norberto Jiménez-Juárez, MC.^I

^IHospital, Dr Daniel Méndez Hernández.
^IIFellow of Paediatric Department.

Dear editor: The clinical characteristics of infection by the novel influenza virus A H1N1/2009 in adults have been spread since the beginning of the pandemic. Nevertheless, this has not occurred thus far in paediatric patients, even though this is an important age group due to medical complications and high rates of hospitalization, as well as its role in transmission, especially by school-age children.

We reviewed the medical files at the paediatric department of the Infectious Diseases Hospital, “National Medical Center La Raza, IMSS,” for patients admitted from April to May 2009 with a hospitalization diagnosis of influenza or probable influenza.

During the process, we found 46 medical files with the diagnosis of influenza. In 34 cases, PCR was performed to detect RNA specific for the novel influenza virus A H1N1/2009.1 We found 16 laboratory-confirmed influenza cases (47.05%). The median age was 30.5 months (range 6-180 months) and only two patients were under 1 year of age; 75% of the cases were under 60 months. Symptoms more frequently reported were cough (87.50%), fever (81.20%), rhinorrhea (75%) and respiratory distress (43.75%); the laboratory variants more frequently reported were leucopenia and thrombocytopenia (both 25%), and 18.75% reported an increase in AST and DHL. Duration of hospitalization was 2 to 12 days (median, 5). Of the 16 laboratoryconfirmed influenza cases, nine patients were previously healthy, two patients had hemato-oncology disease and five patients had diseases not considered a risk factor for influenza.

Though obesity is considered a risk factor for adults, only one hospitalized child was overweight and none were obese, while 10 children were eutrophic and five were malnourished. Four subjects had pneumonitis, one of those had lobar pneumonia and another had multifocal pneumonia. One patient with leukemia developed neutropenic colon and no co-infective microorganism was isolated. None of the patients needed ventilatory assistance using endotracheal intubation, and there were no deaths. All the patients were treated with oseltamivir, dosage according weight, with no adverse reactions by day 5.

After a significant search in PubMed, Scielo, Embase, Latinindex and Medigraphic, no case series were found of pediatric patients with influenza A H1N1/2009; ours is the first reported in Mexico. We observed that the operational definition of the influenza A H1N1/2009 profile was not specific whatsoever. The clinical characteristics considered are the same as those for other respiratory viruses: fever, cough and rhinorrhea. For adults, the operational definition for the clinical diagnosis of influenza or ILI (fever and cough) was not present in four laboratory-confirmed cases. The clinical diagnosis was a challenge, with the majority of cases requiring laboratory confirmation.

The differences between our series and others reported are:^2-5

• Moderate severity and good resolution of clinical disease;

• Concentration of clinical cases in children under 5 years of age without risk factors.

In their epidemiological surveillance, the IMSS⁶ and the Health Department identified the 10 to 19 years age-group as having a higher incidence of influenza A H1N1/2009. Regarding hospitalization rates, children less than 1 year of age had a higher incidence. Our series has some differences as compared to the national trend, possibly because the hospital is a referral medical center.

The clinical features observed are not much different than those reported in the international literature; nevertheless, determining the risk factors for hospitalization and complications due to influenza A H1N1 is a research question that needs to be resolved so that the general physician (first contact) can make the best decision for the patient in terms of shorter follow-up, hospitalization for serious cases, and identifying which patients should be managed with oseltamivir.

References

1. WHO information for laboratory diagnosis of pandemic (H1N1) 2009 virus in humans– update. 2009. (Accessed January 10, 2009). Available at: http://www.who.int/csr/resources/publications/swineflu/WHO_Diagnostic_recommendationsH1N1_20090521.pdf.         [ Links ]

2. Hackett S, Hill L, Patel J, Ratnaraja N,Ifeyinwa A, Farooqi M, et al. Clinical characteristics of paediatric H1N1 admissions in Birmingham, UK. Lancet 2009; 374: 605.         [ Links ]

3. Koliou M, Soteriades ES, Toumasi MM, Demosthenous A, Hadjidemetriou A. Epidemiological and clinical characteristics of influenza A(H1N1) infection in children: The first 45 cases in Cyprus, June-August 2009. Eurosurveillance 2009; 14: 1-3.         [ Links ]

4. O’Riordan S, MB Chir, Barton M, Yau Y. Risk factors and outcomes among children admitted to hospital with pandemic H1N1 influenza. CMAJ 2009. DOI:10.1503/cmaj.091724.         [ Links ]

5. Libster R, Bugna J, Coviello S, Hijano DR, Dunaiewsky M, Reynoso N, et al. Pediatric Hospitalizations Associated with 2009 Pandemic Influenza A (H1N1) in Argentina. NEJM 2010; 362: 45-55.         [ Links ]

6. Echevarría-Zuno S, Mejía-Aranguré JM, Mar- Obeso AJ, Grajales-Muñiz C, Robles-Pérez E, González-León M, et al. Infection and death from influenza A H1N1 virus in Mexico: a retrospective analysis. Lancet 2009 DOI:10.1016/ S0140-6736(09)61638-X        [ Links ]

7. Secretary of Health. Situación Actual de la epidemia. Monografía en Internet. [Accessed February 8, 2010]. Available at: http://portal.salud.gob.mx/sites/salud/descargas/pdf/influenza/ situacion_actual_epidemia_030210.pdf.         [ Links ]