Scientists in Brazil say they have isolated and identified a new strain of the A(H1N1) swine flu virus from a patient who was hospitalized in São Paulo in April and who has since made a complete recovery. The scientists don’t know if the new strain causes more severe infections.
The new strain came from a sample isolated from a 26-year old São Paulo man who started to have symptoms of flu shortly after returning from Mexico. He was hospitalized on 24 April and has since made a full recovery. While in hospital the patient gave a sample for analysis.
A team at the Instituto Adolfo Lutz in São Paulo, led by virologist Dr Terezinha Maria de Paiva, isolated the new strain, A/São Paulo/1454/H1N1, from this sample at the end of April.
Using electron microscopes, another team at Instituto Adolfo Lutz, led by Cecília Luiza Simões, looked at nucleotide sequences in the new strain.
They looked in particular at segments number 4 and 7. Segment 4 codes for the protein Hemagglutinin (HA) which is responsible for virus infectivity and triggers the production of antibodies in the human immune system. Segment 7 codes for the matrix proteins (MP) M1 and M2, which help the virus to develop and maintain its structure.
When they compared segment 4 and segment 7 of the new A/São Paulo/1454/H1N1 strain against the novel swine flu reference strain A/Califórnia/04/H1N1 they found that segment 7 appeared to be “completely conserved” while segment 4 showed a number of discrete alterations in nucleotide and amino acid sequences.
The complete nucleotide sequences for these HA and MP segments have been published in GenBank, the American open access gene sequence database, under access numbers GQ247724 (for the HA gene) and GQ250156 (for the MP).
News of the new strain, together with the newly reported deaths of two people in Argentina to the swine flu virus, have added to fears that South America is heading for a tough winter dominated by the flu pandemic.
Together with the two new deaths in Argentina, there are two in Chile, and another in Colombia, bringing the total number of officially recorded deaths to swine flu in South America to 5.
On Tuesday, Chile’s reported total of lab confirmed cases leapt from 2,355 to 3,125.
Argentina has reported 733 cases, Peru 113, Brazil 69, Ecuador 84 and four other South American countries have reported nearly 120 between them, according to AFP news agency.
The Southern Hemisphere is entering the flu season now, whereas production for the swine flu virus vaccine is still months away from completion, so southern countries will have to face the pandemic without them.
While the current strain appears to cause mostly mild infections with few deaths compared to the number of cases, there are fears that it will mutate to a more severe form. And the worry is, that the more “hosts” that are present in a population without immunity, the bigger the chance that it will mutate.
The last time this happened with a pandemic strain was the 1918 Spanish flu which killed millions of people worldwide. It started as a mild version, mutated to a much deadlier form and then returned in a second wave. And like this new strain of H1N1 swine flu, the group most severely affected was healthy young adults, unlike the seasonal flu which mostly strikes the sick and the elderly.
Sources: AFP, Instituto Adolfo Lutz.
Written by: Catharine Paddock, PhD