Influenza Season Intensifies in the Southern Hemisphere
PAHO Warns of Overlapping Viruses

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On July 1, the Pan American Health Organization (PAHO) issued an “Epidemiological Alert on Seasonal Influenza and Other Respiratory Viruses in the Southern Hemisphere.” With the Southern Hemisphere's winter respiratory season in full swing, influenza activity is rising in several countries, and the alert urges governments to prepare for a growing burden on their health systems.

What happened: the rise of influenza B and co-circulation

The epidemic is centered on influenza A (subtype H3N2), but what the alert flags in particular is that the share of influenza B has risen sharply in recent weeks. This trend is reported to be especially pronounced in Brazil and Chile. H3N2 carries a high risk of severe illness in older adults, while influenza B has a relatively larger impact on children — and the two are spreading at the same time.

On top of that, respiratory syncytial virus (RSV) and the novel coronavirus are co-circulating over the same period. When several viruses spread simultaneously, it becomes harder to tell them apart from symptoms alone, and severe cases tend to concentrate in pediatric wards and ICUs, straining medical resources.

Context: vaccines and regional disparities

PAHO's top priority is vaccination of high-risk groups: older adults, people with underlying conditions, infants, pregnant women, and health-care workers. The vaccine formulation for the Southern Hemisphere is set each year in February and March, and manufacturing and distribution take several months, so by the time of the July alert the peak vaccination period should already be under way. Even so, in many countries the pace of distribution to rural and remote areas lags behind the cities.

PAHO is also asking national governments to strengthen surveillance systems and to prepare pediatric wards and ICUs to receive patients.

My perspective

The first thing I look at when I read this alert is the world of institutional care. In facilities where people with chronic illness or disability live or attend day programs, vaccinating both residents and staff is directly tied to preventing in-house clusters. In Japan's long-term care facilities, group vaccination before winter has become well established, but facilities in Latin America, short-staffed as they are, tend to be caught in a paradox: there simply is no one on hand to organize the vaccination in the first place. From the vantage point of rehabilitation, too, respiratory-infection season is when getting patients out of bed and into training stops, and functional decline in older adults advances all at once. Managing an epidemic is a matter of infection control and, at the same time, a matter of preventing the need for care.

The differences at the level of systems are also worth watching. Countries like Chile and Costa Rica, with relatively strong primary-care vaccination networks, respond to the same PAHO alert at a completely different speed from countries where public health care has been hollowed out by fiscal crisis. Preparedness for an epidemic that “everyone knows will come every year” is a mirror of a country's underlying primary-care capacity.

The indicators to watch are the share of influenza B in PAHO's weekly respiratory-virus situation report, and news of pediatric ICU occupancy rates in Brazil, Chile, and Argentina. Whether the share of influenza B begins to fall by mid-August will determine how high the peak of this season turns out to be.

Glossary

alerta epidemiológica = epidemiological alert. cocirculación = the co-circulation of several viruses. vacunación estacional = seasonal vaccination.

The influenza season, repeating year after year, is an annual exam that tests the underlying strength of a health system.

※ This article is the author’s commentary based on public information. Please confirm the latest figures, dates and procedures with governments and primary sources. Quotations are kept minimal and sources are cited.