# Global Child and Adult Health: Infectious Disease Priorities

## Introduction

Infectious diseases remain the leading cause of morbidity and mortality in low- and middle-income countries (LMICs), disproportionately affecting children under five. While immunization and public health interventions have dramatically reduced deaths from vaccine-preventable diseases, **pneumonia, diarrheal diseases, malaria, tuberculosis, and HIV** continue to drive global health burden. Med-peds physicians with global health interests must understand the epidemiology, prevention, and management of these priority infections across the lifespan.

## The Global Burden of Infectious Disease

| Disease | Annual Deaths (Children <5) | Annual Deaths (All Ages) | Key Prevention | First-Line Treatment |
|---------|---------------------------|-------------------------|---------------|---------------------|
| Pneumonia | ~700,000 | >2.5 million | PCV, Hib vaccine, zinc | Amoxicillin (non-severe); ampicillin + gentamicin (severe) |
| Diarrheal diseases | ~500,000 | ~1.5 million | Rotavirus vaccine, WASH | ORS + zinc supplementation |
| Malaria | ~400,000 | ~600,000 | RTS,S/R21 vaccine, ITNs, SMC | ACTs (uncomplicated); IV artesunate (severe) |
| Tuberculosis | ~200,000 | ~1.3 million | BCG (severe forms) | RIPE regimen |
| HIV/AIDS | ~80,000 | ~650,000 | PMTCT, PrEP | Dolutegravir-based ART |

Infectious diseases account for approximately **4 of the top 10 causes of death** in LMICs. **Under-5 mortality**: ~5 million deaths annually; 50% are due to infectious causes. Leading infectious causes of child death: **pneumonia** (~700,000), **diarrheal diseases** (~500,000), **malaria** (~400,000 in children under 5) **Tuberculosis**: ~1.3 million deaths annually; leading single-agent infectious cause of death globally. **HIV**: ~650,000 deaths annually; pediatric HIV remains a major challenge with 1.7 million children living with HIV.

## Pneumonia

### Pediatric Pneumonia

Leading infectious cause of death in children under 5 worldwide. Major pathogens: **Streptococcus pneumoniae**, **Haemophilus influenzae type b**, **RSV**, influenza. **Integrated Management of Childhood Illness (IMCI)**: WHO algorithm for community and health center-level diagnosis and treatment using respiratory rate, chest indrawing, and danger signs. Treatment: Oral amoxicillin for non-severe pneumonia; parenteral ampicillin plus gentamicin for severe pneumonia. **Prevention**: PCV13/15, Hib vaccine, and zinc supplementation reduce pneumonia incidence and mortality.

### Adult Pneumonia

Leading infectious cause of hospitalization in adults globally. Community-acquired pneumonia pathogens vary by setting; **S. pneumoniae** remains the most common worldwide. **TB must be considered** in any adult with cough >2 weeks in high-prevalence settings. Pneumococcal vaccination and influenza vaccination are key adult preventive strategies. HIV-associated pneumonia: **Pneumocystis jirovecii** pneumonia (PCP) remains a major opportunistic infection.

![Global burden of pneumonia across age groups](illustration-global-pneumonia-burden.jpg)

## Diarrheal Diseases

Second leading cause of death in children under 5; ~500,000 deaths annually. Key pathogens: **Rotavirus**, **Cryptosporidium**, **Shigella**, enterotoxigenic E. coli, cholera. **Oral rehydration solution (ORS)** is the cornerstone of treatment; has saved an estimated 50 million lives since introduction. **Zinc supplementation**: 10-20 mg/day for 10-14 days reduces duration and severity; WHO/UNICEF recommendation. **Rotavirus vaccine**: Has dramatically reduced rotavirus hospitalizations and deaths where introduced. In adults, diarrheal diseases in LMICs are commonly due to contaminated water and food; cholera outbreaks affect all ages. **WASH interventions** (Water, Sanitation, and Hygiene) are critical population-level prevention strategies.

## Malaria

**Plasmodium falciparum** causes the vast majority of malaria deaths; sub-Saharan Africa bears >90% of burden. Most deaths occur in children under 5; severe malaria presents with cerebral malaria, severe anemia, respiratory distress. **Diagnosis**: Rapid diagnostic tests (RDTs) and thick/thin blood smears. **Treatment**: Artemisinin-based combination therapy (ACT) is first-line for uncomplicated falciparum malaria; IV artesunate for severe malaria. **RTS,S/AS01 (Mosquirix)** and **R21/Matrix-M**: WHO-recommended malaria vaccines for children in endemic areas. **Chemoprevention**: Seasonal malaria chemoprevention (SMC) with SP-amodiaquine for children in the Sahel; IPTp with sulfadoxine-pyrimethamine for pregnant women. Adults in endemic areas develop **partial immunity**; malaria in non-immune travelers is a medical emergency.

## Tuberculosis

### Pediatric TB

**1.3 million children** develop TB annually; ~200,000 die. Diagnosis is challenging: children often have **paucibacillary disease** with negative sputum smears. Diagnostic tools: clinical scoring systems, tuberculin skin test (TST), interferon-gamma release assays (IGRAs), GeneXpert MTB/RIF on induced sputum or gastric aspirate. Treatment: Standard four-drug regimen (RIPE: rifampin, isoniazid, pyrazinamide, ethambutol) adapted for weight; shorter regimens for non-severe disease under evaluation. **BCG vaccination**: Provides protection against severe forms (miliary TB, TB meningitis) but does not prevent pulmonary TB.

### Adult TB

10.6 million new cases annually; 1.3 million deaths (2022 WHO data) **HIV-TB coinfection**: TB is the leading cause of death in people living with HIV; all HIV patients should be screened for TB. **Drug-resistant TB**: MDR-TB and XDR-TB require prolonged, toxic regimens; bedaquiline and pretomanid have improved outcomes. **Latent TB infection (LTBI)**: Treatment with isoniazid (9 months) or rifampin (4 months) prevents progression to active disease. TB preventive therapy is recommended for all HIV-positive individuals and household contacts.

## HIV/AIDS

### Pediatric HIV

**Mother-to-child transmission (MTCT)**: Can occur during pregnancy, delivery, or breastfeeding. **Prevention of MTCT (PMTCT)**: Maternal ART during pregnancy and breastfeeding reduces transmission to <2%. **Early infant diagnosis (EID)**: HIV DNA PCR at 4-6 weeks of age; early ART initiation is critical. Children on ART require regular viral load monitoring, growth assessment, and adherence support. **Cotrimoxazole prophylaxis**: Recommended for all HIV-exposed and HIV-infected children to prevent PCP and other opportunistic infections.

### Adult HIV

**Test and treat**: WHO recommends immediate ART initiation regardless of CD4 count. First-line regimens: Dolutegravir-based combinations (TLD: tenofovir, lamivudine, dolutegravir) **Opportunistic infection prophylaxis**: Cotrimoxazole for CD4 <200, isoniazid preventive therapy for LTBI. **Pre-exposure prophylaxis (PrEP)**: Highly effective prevention strategy for high-risk individuals. **Long-acting injectable ART**: Cabotegravir-rilpivirine every 2 months; lenacapavir every 6 months; improving adherence.

![HIV care cascade from testing through viral suppression across ages](illustration-hiv-care-cascade.jpg)

## Neglected Tropical Diseases

Affect >1 billion people globally, predominantly in the poorest communities. **Soil-transmitted helminths**: Mass drug administration with albendazole or mebendazole in school-age children. **Schistosomiasis**: Praziquantel treatment; affects >200 million people. **Visceral leishmaniasis**: Fatal without treatment; liposomal amphotericin B is first-line. **Chagas disease**: Benznidazole treatment; screening of at-risk populations including immigrants.

![Priority infectious diseases and interventions across the lifespan in LMICs](illustration-global-id-priorities.jpg)

## Clinical Pearls

ORS and zinc supplementation remain the most impactful interventions for reducing diarrheal disease mortality in children globally. Malaria vaccines (RTS,S and R21) represent a breakthrough in malaria prevention; they complement but do not replace vector control and chemoprevention. Pediatric TB is underdiagnosed due to paucibacillary disease; a high index of suspicion and contact tracing are essential. PMTCT with maternal ART has dramatically reduced pediatric HIV; early infant diagnosis and treatment are critical for those who acquire HIV. Med-peds physicians working in global health settings must be familiar with WHO treatment algorithms and IMCI guidelines.

## References

1. World Health Organization. *World Health Statistics 2023: Monitoring Health for the SDGs*. WHO; 2023.
2. Bhutta ZA, Das JK, Walker N, et al. Interventions to address deaths from childhood pneumonia and diarrhoea equitably. *Lancet*. 2013;381(9875):1417-1429.
3. World Health Organization. *WHO Consolidated Guidelines on Tuberculosis. Module 5: Management of TB in Children and Adolescents*. WHO; 2022.
4. Datay MI, Boulle A, Mant D,"; Lancet. Global burden of childhood pneumonia and diarrhoea. *Lancet*. 2013;381(9875):1405-1416.