The burden of influenza A and B in Mexico from the year 2010 to 2013: An observational, retrospective, database study, on records from the Directorate General of Epidemiology database

Figures & data

Figure 1. Classification of the population by influenza diagnosis and by ILI and SARI episodes, 2010–2013. Acronyms: ILI, influenza-like illness; SARI, severe acute respiratory infection.

Table 1. Summary of demographic characteristics by influenza status.

	Influenza-positive	Influenza-negative
	N = 20,527	N = 55,558
Sex, male, n (%)	9,578 (46.7)	26,995 (48.6)
Age, years^*
Median (range)	29.0 (0–111)	26.0 (0–109)
Age groups, n (%)
0–4 years	2,618 (12.8)	16,990 (30.7)
5–17 years	3,728 (18.2)	5,779 (10.5)
18–49 years	10,320 (50.4)	19,076 (34.5)
50–64 years	2,540 (12.4)	6,005 (10.9)
≥65 years	1,256 (6.1)	7,442 (13.5)
missing	65 (0.3)	266 (0.5)
Region, n (%)
Center	6,377 (31.1)	16,931 (30.5)
Center-West	4,442 (21.6)	12,913 (23.2)
North	4,963 (24.2)	10,110 (18.2)
South-Southeast	4,745 (23.1)	15,604 (28.1)
Patient type
Ambulatory, n (%)	12,965 (63.2)	21,084 (37.9)
Hospitalized, n (%)	7,562 (36.8)	34,474 (62.1)

* age was available for 20,462 influenza-positive and 55,292 influenza-negative records.

N: Number of ILI+SARI records with samples tested for influenza.

n: number of records within given category.

Acronyms: ILI, influenza-like illness; SARI, severe acute respiratory infection.

Table 2. Summary of outcome by diagnosis, influenza type and season.

		ILI				SARI				Total
		Flu_A		Flu_B		Flu_A		Flu_B		Flu_A		Flu_B
		N = 10764		N = 1490		N = 7806		N = 467		N = 7806		N = 467
Season	Outcome	n	%	n	%	n	%	n	%	n	%	n	%
2010	Death	60	1.7	0	0.0	170	5.8	0	0.0	230	3.6	0	0.0
	Discharged	204	5.8	5	2.0	555	19.0	2	5.7	759	11.8	7	2.4
	Follow-up	773	22.1	43	16.9	42	1.4	5	14.3	815	12.7	48	16.6
	In Treatment	1595	45.5	156	61.4	1740	59.6	10	28.6	335	51.9	166	57.4
	Non severe cases	622	17.7	45	17.7	226	7.7	7	20.0	848	13.2	52	18.0
	Severe cases	249	7.1	4	1.6	177	6.1	11	31.4	426	6.6	15	5.2
	Transferred	2	0.1	1	0.4	8	0.3	0	0.0	10	0.2	1	0.3
	Missing	120	—	7	—	2	—	3	—	122	—	10	—
2011	Death	10	2.4	0	0.0	47	14.6	1	3.1	57	7.8	1	0.5
	Discharged	37	9.0	4	2.2	59	18.3	4	12.5	96	13.1	8	3.7
	Follow-up	79	19.3	49	26.6	2	0.6	2	6.3	81	11.1	51	23.6
	In Treatment	158	38.6	97	52.7	141	43.8	7	21.9	299	40.9	104	48.1
	Non severe cases	90	22.0	20	10.9	35	10.9	8	25.0	125	17.1	28	13.0
	Severe cases	35	8.6	14	7.6	34	10.6	10	31.3	69	9.4	24	11.0
	Transferred	0	0.0	0	0.0	4	1.2	0	0.0.	4	0.5	0	0.0
	Missing	7	—	8	—	0	—	0	—	7	—	8	—
2012	Death	59	1.4	1	0.1	256	9.4	6	2.7	315	4.5	7	0.8
	Discharged	262	6.0	20	2.9	749	27.4	47	21.0	1011	14.3	67	7.3
	Follow-up	1445	33.2	138	20.1	42	1.5	2	0.9	1487	21.0	140	15.4
	In Treatment	1926	44.3	436	63.4	1093	40.1	86	38.4	3019	42.7	522	57.2
	Non severe cases	490	11.3	76	11.0	333	12.2	52	23.2	823	11.6	128	14.0
	Severe cases	155	3.6	17	2.5	239	8.8	31	13.8	394	5.6	48	5.3
	Transferred	10	0.2	0	0.0	17	0.6	0	0.0	27	0.4	0	0.0
	Missing	206	—	3	—	7	—	0	—	213	—	3	—
2013	Death	79	3.6	4	1.2	245	13.4	6	3.5	324	8.1	10	1.9
	Discharged	249	11.5	33	9.5	519	28.4	40	23.1	768	19.2	73	14.1
	Follow-up	498	22.9	96	27.7	20	1.1	2	1.2	518	13.0	98	18.9
	In Treatment	1000	46.1	173	50.0	636	34.8	75	43.4	1636	40.9	248	47.8
	Non severe cases	238	11.0	25	7.2	279	15.3	31	17.9	517	12.9	56	10.8
	Severe cases	104	4.8	14	4.0	117	6.4	19	11.0	221	5.5	33	6.4
	Transferred	2	1	1	0.3	12	0.7	0	0.0	14	0.4	1	0.2

ILI = Episodes with influenza like illness.

SARI = Episodes with severe acute respiratory infection.

Flu_A = Episodes positive for Influenza A.

Flu_B = Episodes positive for Influenza B.

N = number of episodes.

n = number of episodes in a given category.

% = n / Number of episodes with available results × 100.

Figure 2. Seasonal pattern of laboratory-confirmed influenza A or B activity, 2010–2013.

Figure 3. Summary of context, outcomes and impact for healthcare providers.

Table 3. Occurrence of influenza A and B by age group, within all ILI+SARI records, 2010–2013.

		Influenza A
	ILI+SARI records	All subtypes^*		subtype H1N1		subtype H3N2		Influenza B
	N	n	% (95%CI)	n	% (95%CI)	n	% (95%CI)	n	% (95%CI)
Overall	76,085	18,570	24.4 (24.1–24.7)	10,510	13.8 (13.6–14.1)	4,019	5.3 (5.1–5.4)	1,957	2.6 (2.5–2.7)
Age groups
0–4 years	19,608	2,296	11.7 (11.3–12.2)	1,021	5.2 (4.9–5.5)	581	3.0 (2.7–3.2)	322	1.6 (1.5–1.8)
5–17 years	9,507	3,030	31.9 (30.9–32.8)	1,758	18.5 (17.7–19.3)	710	7.5 (6.9–8.0)	698	7.3 (6.8–7.9)
18–49 years	29,396	9,624	32.7 (32.2–33.3)	5,824	19.8 (19.4–20.3)	1,856	6.3 (6.0–6.6)	696	2.4 (2.2–2.5)
50–64 years	8,545	2,393	28.0 (27.1–29.0)	1,467	17.2 (16.4–18.0)	440	5.1 (4.7–5.6)	147	1.7 (1.5–2.0)
≥65 years	8,698	1,168	13.4 (12.7–14.2)	409	4.7 (4.3–5.2)	417	4.8 (4.4–5.3)	88	1.0 (0.8–1.2)
Years
2010	21,911	6,545	29.9 (29.3–30.5)	2,202	10.0 (9.7–10.5)	1,604	7.3 (7.0–7.7)	299	1.4 (1.2–1.5)
2011	10,159	738	7.3 (6.8–7.8)	375	3.7 (3.3–4.1)	162	1.6 (1.4–1.9)	224	2.2 (1.9–2.5)
2012	23,823	7,289	30.6 (30.0–31.2)	6,093	25.6 (25.0–26.1)	440	1.8 (1.7–2.0)	915	3.8 (3.6–4.1)
2013	20,192	3,998	19.8 (19.3–20.4)	1,840	9.1 (8.7–9.5)	1,813	9.0 (8.6–9.4)	519	2.6 (2.4–2.8)

* H1N1 + H3N2 + A/not subtyped.

N: Number of ILI+SARI records with samples tested for influenza (diagnosis might be + or -).

n: number of records within given category.

%: percentage within diagnosed cases = 100*n/N for each given category.

Acronyms: CI, confidence interval; ILI, influenza-like illness; SARI, severe acute respiratory infection.

Table 4. Influenza-positive diagnoses, A, B or both, per ILI+SARI records, by influenza seasons.

	ILI+SARI records N	Influenza (A+B) diagnoses, n (%)	Influenza A diagnoses, n (%)	Influenza B diagnoses, n (%)
Jan 2010–Mar 2010	9,576	2,370 (24.7)	2,359 (24.6)	11 (0.1)
Apr 2010–Mar 2011	15,829	5,005 (31.6)	4,530 (28.6)	475 (3.0)
Apr 2011–Mar 2012	22,462	7,360 (32.8)	7,247 (32.3)	113 (0.5)
Apr 2012–Mar 2013	13,939	3,012 (21.6)	1,825 (13.1)	1,187 (8.5)
Apr 2013–Dec 2013	14,279	2,780 (19.5)	2,609 (18.3)	171 (1.2)

N: Number of ILI+SARI records with samples tested for influenza (diagnosis might be + or -).

n: number of records within given category.

%: percentage within diagnosed cases = 100*n/N for each given category.

Acronyms: ILI, influenza-like illness; SARI, severe acute respiratory infection.